Chapter 01: Ecosystem

Environment

Ø Environment stands for surroundings. Environment has been defined as ‗the sum

Ø total of all conditions and influences that affect the development of organisms‘. This definition stresses on the totality of environment, implying that every organism including human beings, has its own environment.

Ø A number of terms have often been used as synonyms of geographical environment. These synonyms include habitat, ecology, population-ecology, ecosystem, nutrient cycle, biodiversity, geosphere (zone of life) and ecosphere. In other words, environment is an inseparable whole, consisting of mutually interacting systems of physical and biological elements.

Ø The physical elements include space, landforms, water-bodies, climate, drainage, rocks, soils, mineral wealth, etc., while the biological elements include man, fauna and flora, including micro-organisms.

Experts recognise the following broad categories of environment:

Categories of Environment

1. Physical Environment: The non-living components of environment include landforms, climate, water-bodies, temperature, humidity, air, etc.

2. Cultural Environment: The creations of man on the earth‘s surface are known as cultural Environment or man-made environment.

3. Biological Environment: The biological environment consists of human beings, fauna, flora and micro-organisms.

4. Cognitive Environment or Subjective Environment (Mental Map): The perceived environment is known as cognitive or subjective environment. It differs from person to person. For example, a field has different meanings for a sheep keeper, vegetable grower, grain farmer, rubber planter, industrialist, and builder of colonies.

Salient Features of Environment

The salient features of environment are given below:

(i) At any given point of time, environment is the sum of biotic and abiotic elements.

(ii) Biodiversity, habitat and energy constitute the three basic components of the structure of an environment.

(iii) Environment changes in space and time.

(iv) It is based on the interactive and functional relationship between biotic and abiotic components.

(v) The working of an environment and its dependent systems are governed by the flow of energy.

(vi) Environment generates its own organic matter which differs in space, from region to region and climate to climate.

(vii) Environment tends to maintain an ecological balance.

Habitat

Ø Habitat is the physical environment in which an organism lives (it corresponds to address of an organism).

Ø It is an ecological or environmental area inhabited by particular species of plants, animals, fungi, etc. Many habitats make up the environment.

Ø

A single habitat may be common for more than one organism which have similar requirements.

Ø For example, a single aquatic habitat may support a fish, frog, crab, phytoplankton and many other kinds of organisms.

Ø The various species sharing a habitat thus have the same ‗address‘. Forest, river etc. are other examples of habitat.

Ø All habitats are environments but all environments are not habitats

Man and Environment

Ø Geography often been defined as the study of man‘s relationship with the environment. According to Miss Semple—a leading American geographer of the early 20th century, ‗ Man is the product of earth or his environment‘. In 1859, Charles Darwin showed that life developed under the selective action of natural forces. It determines scientifically the position of man as a creature adapted to his environment.

Ø This approach, for the first time was applied by the German geographer—F. Ratzel in anthropology (Human) and political geography. This scientific position of man resulted into the ‗Deterministic School of Thought‘. The point of view of the followers of determinism is that the environment controls the course of human action. In other words, it is the belief that variations in human behaviour around the world can be explained by differences in physical environment and geographical settings.

Biosphere:

Ø The biosphere is the biological component (supporting life) of earth which includes the lithosphere, hydrosphere and atmosphere.

Ø The biosphere includes all living organisms on earth, together with the dead organic matter produced by them.

Ø Biosphere is absent at extremes of the North and South poles, the highest mountains and the deepest oceans, since existing hostile conditions there do not support life [Life is the characteristic feature of biosphere].

Ø

Occasionally spores of fungi and bacteria do occur at great height beyond 8,000 metres, but they are metabolically inactive, and hence represent only dormant life.

Ecosystem:

Ø The term Ecosystem was formally proposed by Tansley, a plant ecologist in 1935.

Ø A system of organisms functioning together with their non-living environment.

Ø An ecosystem can be visualised as a functional unit of nature, where living organisms [producers, consumers, and decomposers] interact among themselves and also with the surrounding physical environment.

Ø Ecosystem varies greatly in size from a small pond to a large forest or a sea.

Ø Forest, grassland and desert are some examples of terrestrial ecosystems; pond, lake, wetland, river and estuary are some examples of aquatic ecosystems. Crop fields and an aquarium may also be considered as man-made ecosystems.

Ø In the ecosystem, biotic and abiotic components are linked together through nutrient cycles and energy flows.

Ø An ecosystem can be of any size but usually encompasses specific and limited species. E.g.: Aquatic Ecosystem. [This is how ecosystem is different from Environment]

Ø Everything that lives in an ecosystem is dependent on the other species and elements that are also part of that ecological community. If one part of an ecosystem is damaged or disappears, it has an impact on everything else.

Difference Between Ecology, Environment & Ecosystem

Ø Ecology is the study of the ecosystems and the environment.

Ø Environment is a group of ecosystems.

Ø Ecosystem is a functional unit of environment (mostly biosphere).

Ø Environment → Can be Almost Everything or a Small region

Ø Habitat → Area where an organism lives.

Ø Biosphere → The region on earth that supports life.

Ø Ecosystem → Producers, Consumers, Decomposers and their relationships (tiny environment). It is the functional unit of the environment

Ø A community of organisms together with the environment in which they live – ecosystem.

Ø The flora and fauna of a geographical area – biodiversity

Components of an Ecosystem

The components of the ecosystem are categorized into abiotic or non-living and biotic or living components. Both the components of ecosystem and environment are same.

Abiotic components:

Ø Abiotic components are the inorganic and non-living parts which act as major limiting factors

Effect Of Abiotic Components On Terrestrial Primary Producers – Plants

Ø Plants are the reason that the other animals are able to survive on land. So the effect of abiotic factors on plants is crucial.

Light

Ø Extremely high intensity favors root growth than shoot growth which results in

increased transpiration, short stem, smaller thicker leaves.

Ø On the other hand low intensity of light retards growth, flowering and fruiting.

Ø When the Intensity of light is less than the minimum, the plants ceases to grow due to

accumulation of CO2 and finally dies.

Ø Out of 7 colours in the visible part of spectrum, only red and blue are effective in photosynthesis.

Ø Plant grown in blue light are small, red light results in elongation of cells results in etiolated plants. Plants grown in ultraviolet and violet light are dwarf.

Frost

Ø Frost results in freezing the soil moisture. The plants growing in such soil, get exposed to direct sun light in the morning, they are killed due to increased transpiration when their roots are unable to supply moisture. This is the main reason for innumerable death of sal seedlings.

Ø As a result of frost, water in the intercellular spaces of the plant gets frozen into ice which withdraws water from the interior of the cells. This results in increasing concentration of salts and dehydration of cells. Thus coagulation and precipitation of the cell colloid results in death of plant. Also, frost leads to formation of canker.

Snow

Ø Snow acts as blanket, prevents further drop in temperature and protects Page seedlings from excessive cold and frost.

Ø Accumulation of snow on tree parts can break the branches or even uproot the tree.

Ø Snow shortens the period of vegetative growth.

Temperature

Ø High temperature results in death of plant due to coagulation of protoplasmic proteins [Some bacteria can survive high temperatures because of their protoplasmic proteins that don‘t coagulate at normally high temperatures].

Ø High temperature disturbs the balance between respiration and photo synthesis thereby causes depletion of food resulting in greater susceptibility to fungal and bacterial attack.

Ø It also results in desiccation of plant tissues and depletion of moisture.

Biotic Components

Primary producers - Autotrophs (self-nourishing)

Ø Primary producers are basically green plants, certain bacteria and algae that carry out photosynthesis.

Ø In terrestrial ecosystem, grasses, plants and trees are the primary producers.

Ø while in aquatic ecosystem, microscopic algae [plankton] are the primary producers.

Consumers — Heterotrophs or Phagotrophs (other nourishing)

Ø Consumers are incapable of producing their own food. They depend on organic food derived from plants, animals or both.

Ø Consumers can be divided into two broad groups namely micro and macro consumers.

Macro consumers

Ø Herbivores are primary consumers which feed mainly on plants e.g. cow. Secondary consumers feed on primary consumers e.g. wolves, dogs, etc.

Ø Carnivores which feed on both primary and secondary consumers are called tertiary consumers e.g. lion which can eat wolves, snakes etc.

Ø Omnivores are organisms which consume both plants and animals e.g. man, bear, etc.

Micro consumers - Saprotrophs (decomposers or osmotrophs)

Ø They are bacteria and fungi which obtain energy and nutrients from dead organic substances (detritus) of plant and animals.

Ø The products of decomposition such as inorganic nutrients which are released in the ecosystem are reused by producers and thus recycled.

Ø Earthworm and certain soil organisms (such as nematodes, and arthropods) are detritus feeders and help in the decomposition of organic matter and are called detrivores

Classification of Ecosystems

Functions Of An Ecosystem

Ø The function of an ecosystem include

o Energy flow through food chain

o Nutrient cycling (biogeochemical cycles)

o Ecological succession or ecosystem development

o Homeostasis (or cybernetic) or feedback control mechanisms

Ø Each will be discussed in detail in the subsequent posts.

Ecology

Ø The term ecology was derived from two. Greek words ‗Oikos‘ meaning home and ‗logos‘ meaning study.

Ø Ecology is a science that deals with the complex and dynamic relationships between organisms and their environment, the two components of nature which are interdependent, mutually reactive and inter-related.

Ø Ecology is the branch of biology concerned with the relations of organisms to one another (energy flow and mineral cycling) and to their physical surroundings (environment).

Ø Literally ecology means the study of the earth's "house-holds" including the plants, animals, microorganisms, people and their environment existing together as interdependent components, as well as the energy flows and material cycles in the physical and biological environment.

Ø Ecology encompasses study of individual, organisms, population, community, ecosystem, biome and biosphere which form the various levels of ecological organization.

Ø The Indian texts of Vedas, the Samhitas, the Brahmanas and the Aranyakas- Upanishads contain many references to ecological concepts. The Indian treatise on medicine, the Caraka-Samhita and the surgical text Susruta-Samhita, show that people during this period had a good understanding of plant and animal ecology.

Levels Of Organizations In Ecology

Ø Ecology not only deals with the study of the relationship of individual organisms with their environment, but also with the study of populations, communities, ecosystems, biomes, and biosphere as a whole Individual: Organism is an individual living being that has the ability to act or function independently. It may be any organism.

Ø Species: Species are a group of living organisms consisting of similar individuals capable of exchanging genes or of interbreeding, considered as the basic unit of taxonomy and denoted by a Latin binomial, e.g. Homo sapiens.

Ø Population: Population is a community of interbreeding organisms [same species], occupying a defined area during a specific time.

Ø Population growth rate is the percentage variation between the number of individuals in a population at two different times. It can be positive due to birth and/or immigration or negative due to death and/or emigration.

Ø The number of individuals per unit area at a given time is termed as population density.

Ø In case of large, mobile animals like tigers, leopards, lions, deer etc., the density may be determined by counting individual animals directly or by the pugmarks (foot imprints) left by the animals in a defined area.

Ø Pugmarks of each individual animals are unique and different from one others. Study of pug marks can provide the following information reliably if analyzed skillfully:

Ø Presence of different species in the area of study.

Ø Identification of individual animals.

Ø Population of large cats (tigers, lions etc.).

Ø Sex ratio and age (young or adult) of large cats. [Even sex of tigers can be determined using pugmarks. http://assets.wwfindia.org/downloa ds/reading_pugmarks.pdf also says the same]

Ø Community: Communities in most instances are named after the dominant plant form (species). For example: A grassland community is dominated by grasses, though it may contain herbs, shrubs, and trees, along with associated insects and animals of different species. A community is not fixed or rigid.

Ø On the basis of size and degree of relative independence communities may be divided into two types: Major Communities and Minor Communities.

Ø Major Communities: These are large sized and relatively independent. They depend only on the sun‘s energy from outside. Eg: Tropical evergreen forests.

Ø Minor Communities: These are dependent on neighboring communities and are often called societies. They are secondary aggregations within a major community. Eg: A mat of lichen on a cow dung pad.

Ø Ecosystem: An ecosystem is a community of organisms interacting with each other and with their environment such that energy is exchanged and system-level processes, such as the cycling of elements, emerge.

Ø Biome: Biome is a large naturally occurring community of flora and fauna occupying a major habitat. E.g. Rainforest biome or tundra biome.

Ø Plants and animals in a biome have common characteristics due to similar climates and can be found over a range of continents.

Ø Biomes are distinct from habitats, because any biome can comprise a variety of habitats (habitat: the natural home or environment of an organism).

Ø Biosphere: The biosphere is the biological component of earth which includes lithosphere, hydrosphere and atmosphere. The biosphere includes all living organisms on earth, together with the organic matter produced by them.

Principles of Ecology

Ø On planet Earth, life exists not just in a few favourable habitats but even in extreme and harsh habitats – scorching Rajasthan desert, perpetually rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, permafrost polar regions, high mountain tops, boiling thermal springs, and stinking compost pits, to name a few. Even our intestine is a unique habitat for hundreds of species of microbes. How is this possible?

Adaptation

Ø Each organism is adapted to its particular environment. An adaptation is thus, ―the appearance or behavior or structure or mode of life of an organism that allows it to survive in a particular environment‖. E.g. Neck of a giraffe.

Ø Adaptation is any attribute of the organism (morphological – when trees grew higher, the giraffes neck got longer; physiological – in the absence of an external source of water, the kangaroo rat in North American deserts is capable of meeting all its water requirements through its internal fat oxidation; behavioral – animals migrating temporarily to a less stressful habitat) that enables the organism to survive and reproduce in its habitat.

Ø We need to breathe faster when we are on high mountains. After some days, our body adjusts to the changed conditions on the high mountain.

Ø Such small changes that take place in the body of a single organism over short periods, to overcome small problems due to changes in the surroundings, are called acclimatization.

Examples of Adaptation

Ø Many adaptations have evolved over a long evolutionary time and are genetically fixed.

Ø In the absence of an external source of water, the kangaroo rat in North American deserts is capable of meeting all its water requirements through its internal fat oxidation (in which water is a byproduct).

Ø It also has the ability to concentrate its urine so that minimal volume of water is used to remove excretory products.

Ø Many desert plants have a thick cuticle on their leaf surfaces and have their stomata arranged in deep pits to minimise water loss through transpiration.

Ø They also have a special photosynthetic pathway (CAM) that enables their stomata to remain closed during day time.

Mutation

Ø Mutation (a change in genetic material that results from an error in replication of DNA) causes new genes to arise in a population.

Ø Further, in a sexually reproducing population, meiosis and fertilization produce new combination of genes every generation, which is termed recombination.

Ø Thus members of the same species show ‗variation‘ and are not exactly identical. Variations are heritable.

Natural Selection

Ø Natural Selection is the mechanism proposed by Darwin and Wallace. Natural selection is the process by which species adapt to their environment.

Ø It is an evolutionary force that selects among variations i.e. genes that help the organism to better adopt to its environment. Such genes are reproduced more in a population due to natural selection.

Ø Those off springs which are suited to their immediate environment have a better chance of surviving, reaching reproductive age and passing on the suitable adaptations to their progeny

Ecotone

Ø An ecotone is a zone of junction or a transition area between two biomes [diverse ecosystems]. It is where two communities meet and integrate.

Ø For e.g. the mangrove forests represent an ecotone between marine and terrestrial ecosystem. Other examples are grassland (between forest and desert), estuary (between fresh water and salt water) and river bank or marsh land (between dry and wet).

Characteristics of Ecotone

Ø It may be narrow (between grassland and forest) or wide (between forest and desert).

Ø As it is a zone of transition, it has conditions intermediate to the adjacent ecosystems. Hence it is a zone of tension.

Ø Usually, the number and the population density of the species of an outgoing community decreases as we move away from community or ecosystem.

Ø A well-developed ecotones contain some organisms which are entirely different from that of the adjoining communities.

Ecological Niche

Ø Niche refers to the unique functional role and position of a species in its habitat or ecosystem.

Ø In nature, many species occupy the same habitat but they perform different functions

Ø The functional characteristics of a species in its habitat is referred to as ―niche‖ in that common habitat. Habitat of a species is like its ‗address‘ (i.e. where it lives) whereas niche can be thought of as its ―profession‖ (i.e. activities and responses specific to the species).

Ø A niche is unique for a species while many species share the habitat. No two species in a habitat can have the same niche. This is because of the competition with one another until one is displaced.

Ø For example, a large number of different species of insects may be pests of the same plant but they can co-exist as they feed on different parts of the same plant

Ecological Succession

Ø Biotic communities are dynamic in nature and change over a period of time. The process by which communities of plant and animal species in an area are replaced or changed into another over a period of time is known as ecological succession.

Ø

Succession is a universal process of directional change in vegetation, on an ecological scale.

Ø Succession occurs when a series of communities replace one another due to large scale destruction (natural or manmade). This process continues with one community replacing another, until a stable, mature community develops.

Primary Succession

Ø Primary succession takes place an over a bare or unoccupied areas such as rocks outcrop, newly formed deltas and sand dunes, emerging volcano islands and lava flows as well as glacial moraines (muddy area exposed by a retreating glacier) where no community has existed previously.

Ø In primary succession on a terrestrial site the new site is first colonized by a few hardy pioneer species that are often microbes, lichens and mosses. The pioneers over a few generations alter the habitat conditions by their growth and development.

Secondary Succession

Ø Secondary succession occurs when plants recognize an area in which the climax community has been disturbed.

Ø Secondary succession is the sequential development of biotic communities after the

complete or partial destruction of the existing community.

Ø A mature or intermediate community may be destroyed by natural events such as floods, droughts, fires, or storms or by human interventions such as deforestation, agriculture, overgrazing, etc.

Ø This abandoned farmland is first invaded by hardy species of grasses that can survive in bare, sunbaked soil. These grasses may be soon joined by tall grasses and herbaceous plants. These dominate the ecosystem for some years along with mice, rabbits, insects and seed-eating birds.

Ø Eventually, some trees come up in this area, seeds of which may be brought by wind or animals. And over the years, a forest community develops. Thus an abandoned farmland over a period becomes dominated by trees and is transformed into a forest.

Trophic Levels

Energy Flow Through an Ecosystem – Trophic Levels:

Ø A food chain is the sequence of energy transfer from the lower levels to the upper or higher trophic levels through complex network of interconnected food chains.

Ø It is the way an organism obtains and sustain physical, chemical and biological factors it needs to survive. Basically, as stated above, all animals depend on plants for their food.

Ø For instance, foxes may eat rabbits, but rabbits feed on grass. Similarly, a hawk eats a lizard, the lizard had just eaten a grasshopper and the grasshopper was feeding on grassblades.

Ø the leaf, the blue-tit eats the caterpillar, but may fall prey to the kestrel. In other words, the food-web is really an energy flow system, tracing the path of solar energy through the ecosystem.

Ø The circuit along which energy flows from producers (who manufacture their own food) to consumers is a one-directional flow of chemical energy, ending with decomposition.

Ø

This relationship is called food-chain. Another example of a food chain is that a caterpillar eats

Ø The flow of energy from producer to top consumers is called energy flow which is

unidirectional.

Ø To understand the energy flow through the ecosystem we need to study about the trophic levels [tropical level interaction].

Ø Trophic level is the representation of energy flow in an ecosystem. The trophic level of an organism is the position it occupies in a food chain.

Ø Trophic level interaction deals with how the members of an ecosystem are connected based on nutritional needs.

Trophic levels

Autotrophs

Green plants (producers)

Heterotrophs

Herbivore (primary consumers)

Heterotrophs

Carnivores (secondary consumers)

Heterotrophs

Carnivore (tertiary consumers)

Heterotrophs

Top carnivores (Quaternary consumers)

Ø Energy flows through the trophic levels from producers to subsequent trophic levels is unidirectional.

Ø Energy level decreases from the first trophic level upwards due to loss of energy in the form of heat at each trophic level.

Ø This energy loss at each tropic level is quite significant. Hence there are usually not more than four-five trophic levels [beyond this the energy available is negligible to support an organism].

The trophic level interaction involves three concepts namely

1. Food Chain

2. Food Web

3. Ecological Pyramids Food Chain:

Ø Transfer of food energy from green plants (producers) through a series of organisms with repeated eating and being eaten link is called a food chain.

Ø E.g. Grasses → Grasshopper → Frog → Snake → Hawk/Eagle.

Ø Each step in the food chain is called trophic level. A food chain starts with producers and ends with top carnivores.

Ø The trophic level of an organism is the position it occupies in a food chain.

Types of Food Chains Grazing food chain

Ø The consumers which start the food chain, utilizing the plant or plant part as their food, constitute the grazing food chain. This food chain begins from green plants

at the base and the primary consumer is herbivore.

Ø For example, In terrestrial ecosystem, grass is eaten by caterpillar, which is eaten by lizard and lizard is eaten by snake.

Ø In Aquatic ecosystem phytoplankton (primary producers) are eaten by zoo planktons which are eaten by fishes and fishes are eaten by pelicans.

Detritus food chain

Ø This type of food chain starts from dead organic matter of decaying animals and plant bodies.

Ø Dead organic matter or detritus feeding organisms are called detrivores or decomposer. The detrivores are eaten by predators.

Ø The two food chains are linked. The initial energy source for detritus food chain is the waste materials and dead organic matter from the grazing food chain.

Ø In an aquatic ecosystem, grazing food chain is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain.

Ø Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism.

Ø Humification and mineralization occur during decomposition in the soil.

Ø Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.

Ø Being colloidal in nature, humus serves as a reservoir of nutrients. The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralization.

Ø Warm and moist environment favor decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in buildup of organic materials.

Food Web:

Ø

Multiple interlinked food chains make a food web. Food web represents all the possible paths of energy flow in an ecosystem.

Ø If any of the intermediate food chain is removed, the succeeding links of the chain will be affected largely.

Ø The food web provides more than one alternative for food

to most of the organisms in an ecosystem and therefore increases their chance of survival.

Ø Also food availability and preferences of food of the organisms may shift seasonally e.g. we eat watermelon in summer and peaches in the winter. Thus there are interconnected networks of feeding relationships that take the form of food webs.

Ecological Pyramids:

Ø The pyramidal representation of trophic levels of different organisms based on their ecological position [producer to final consumer] is called as an ecological pyramid.

Ø The food producer forms the base of the pyramid and the top carnivore forms the tip. Other consumer trophic levels are in between.

Ø The pyramid consists of a number of horizontal bars depicting specific trophic levels. The length of each bar represents the total number of individuals or biomass or energy at each trophic level in an ecosystem.

The ecological pyramids are of three categories.

1. Pyramid of numbers,

2. Pyramid of biomass

3. Pyramid of energy or productivity

Pyramid of Numbers

Ø Pyramid of numbers represents the total number of individuals of different species (population) at each trophic level.

Ø Depending upon the size, the pyramid of numbers may not always be upright and may even be completely inverted.

Ø It is very difficult to count all the organisms, in a pyramid of numbers and so the pyramid of number does not completely define the trophic structure for an ecosystem.

Pyramid of numbers – upright

Ø In this pyramid, the number of individuals is decreased from lower level to higher trophic level.

Ø This type of pyramid can be seen in grassland ecosystem and pond ecosystem.

Ø The grasses occupy the lowest trophic level (base) because of their abundance.

Ø The next higher trophic level is primary consumer - herbivore (example - grasshopper).

Ø The individual number of grasshopper is less than that of grass. The next energy level is primary carnivore (example - rat).

Ø The number of rats are less than grasshopper, because, they feed on grasshopper. The next higher trophic level is secondary carnivore (example - snakes). They feed on rats.

Ø The next higher trophic level is the top carnivore. (Ex: Hawk). With each higher trophic level, the number of individual decreases.

Pyramid of numbers – inverted

Ø In this pyramid, the number of individuals is increased from lower level to higher trophic level. E.g. Tree ecosystem.

Pyramid of Biomass

Ø Pyramid of biomass is usually determined by collecting all organisms occupying each trophic level separately and measuring their dry weight.

Ø This overcomes the size difference problem because all kinds of organisms at a trophic level are weighed. Biomass is measured in g/m2.

Ø The biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate.

Ø Each trophic level has a certain mass of living material at a particular time called as the standing crop.

Ø The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area.

Pyramid of Biomass – Upright

Ø For most ecosystems on land, the pyramid of biomass has a large base of primary producers with a smaller trophic level perched on top.

Ø The biomass of producers (autotrophs) is at the maximum. The biomass of next trophic level i.e. primary consumers is less than the producers. The biomass of next higher trophic level i.e. secondary consumers is less than the primary consumers. The top, high trophic level has very less amount of biomass.

Pyramid of Biomass – Inverted

Ø In contrast, in many aquatic ecosystems, the pyramid of biomass may assume an inverted form. [Pyramid of numbers for aquatic ecosystem is upright]

Ø This is because the producers are tiny phytoplankton that grow and reproduce rapidly.

Ø Here, the pyramid of biomass has a small base, with the consumer biomass at any instant actually exceeding the producer biomass and the pyramid assumes inverted shape.

Ø To compare the functional roles of the trophic levels in an ecosystem, an energy pyramid is most suitable.

Ø An energy pyramid represents the amount of energy at each trophic level and loss of energy at each transfer to another trophic level. Hence the pyramid is always upward, with a large energy base at the bottom.

Ø Suppose an ecosystem receives 1000 calories of light energy in a given day. Most of the energy is not absorbed; some is reflected back to space; of the energy absorbed only a small portion is utilized by green plants, out of which the plant uses up some for respiration and of the 1000 calories, therefore only 100 calories are stored as energy rich materials.

Ø Now suppose an animal, say a deer, eats the plant containing 100 calorie of food energy. The deer uses some of it for its own metabolism and stores only 10 calorie as food energy. A lion that eats the deer gets an even smaller amount of energy. Thus usable energy decreases from sunlight to producer to herbivore to carnivore. Therefore, the energy pyramid will always be upright.

Energy pyramid:

Ø

Concept helps to explain the phenomenon of biological magnification - the tendency for toxic substances to increase in concentration progressively with higher trophic levels.

Ecological Efficiency

Ecological efficiency describes the efficiency with which is transferred from one trophic level to the next.

The number of trophic levels in the grazing food chain is restricted as the transfer of energy follows 10 per cent law – only 10 per cent of the energy is transferred to each trophic level. The decreases at each subsequent trophic level are due to two reasons:

1. At each trophic a part of the available energy is lost in respiration or used up in metabolism.

2. A part of energy is lost at each transformation, i.e. when it moves from lower to higher trophic level as heat.

Limitations of Ecological Pyramids

Ø It does not take into account the same species belonging to two or more trophic levels.

Ø It assumes a simple food chain, something that almost never exists in nature; it does not accommodate a food web.

Ø Moreover, saprophytes (plant, fungus, or microorganism that lives on decaying matter) are not given any place in ecological pyramids even though they play a vital role in the ecosystem.

Chlorinated Hydrocarbons (CHC) or Organochloride – Pollutants And Trophic Level:

Ø Pollutants, especially non-degradable ones move through the various trophic levels in an ecosystem. Non-degradable pollutants mean materials, which cannot be metabolized by the living organisms. Example: Chlorinated Hydrocarbons.

Ø ChlorinatedHydrocarbons or Organochloride or CHC are hydrocarbons whose some or most hydrogen atoms have been replaced by chlorine atoms. E.g. DDT, endosulfan etc.).

Ø A variety of simple chlorinated hydrocarbons including dichloromethane, chloroform,

and carbon tetrachloride.

Applications of CHC

Ø Production of vinyl chloride almost all of which was converted into polyvinylchloride (PVC) [PVC pipes].

Ø Chloroform, dichloromethane, dichloroethene, and trichloroethane are useful solvents. These solvents are immiscible with water and effective in cleaning applications such as degreasing and dry cleaning.

Ø Pesticides and insecticides such as DDT, heptachlor, and endosulfan are CHCs.

Effects of CHC

Ø Dioxins (highly toxic organic compound produced as a by-product in some manufacturing processes), produced when organic matter is burned in the presence of chlorine, and some insecticides, such as DDT, are persistent organic pollutants.

Ø DDT, which was widely used to control insects in the mid-20th century, accumulates in food chains, and causes reproductive problems (e.g., eggshell thinning) in certain bird species.

Ø DDT residues continue to be found in humans and mammals across the planet many years after production and use have been limited.

Ø In Arctic areas, particularly high levels are found in marine mammals. These chemicals concentrate in mammals, and are even found in human breast milk.

Ø In some species of marine mammals, particularly those that produce milk with a high fat content, males typically have far higher levels, as females reduce their concentration by transfer to their offspring through lactation.

Ø Endosulfan became a highly controversial agrichemical due to its acute toxicity and potential for bioaccumulation, and role as an endocrine disruptor (enables the effect of estrogens causing reproductive and developmental damage in both animals and humans).

Ø Because of its threats to human health and the environment, a global ban on the manufacture and use of endosulfan was negotiated under the Stockholm Convention in April 2011.

Movement of these pollutants involves two main processes:

1. Bioaccumulation.

2. Biomagnification.

Bioaccumulation:

Ø It refers to how pollutants enter a food chain.

Ø In bioaccumulation there is an increase in concentration of a pollutant from the environment to the first organism in a food chain.

Bio magnification:

Ø Bio magnification refers to the tendency of pollutants to concentrate as they move from one trophic level to the next.

Ø Thus in bio magnification there is an increase in concentration of a pollutant from one link in a food chain to another.

Ø In order for bio magnification to occur, the pollutant must be: long-lived, mobile, soluble in fats, biologically active. E.g. DDT.

Ø If a pollutant is short-lived, it will be broken down before it can become dangerous.

Ø If it is not mobile, it will stay in one place and is unlikely to be taken up by organisms.

Ø If the pollutant is soluble in water, it will be excreted by the organism. Pollutants that

dissolve in fats, however, may be retained for a long time.

Ø It is traditional to measure the amount of pollutants in fatty tissues of organisms such as fish.

Ø In mammals, we often test the milk produced by females, since the milk has a lot of fat in it and is often more susceptible to damage from toxins (poisons).

Biotic Interaction:

Ø The interaction that occurs among different individuals of the same species is called intraspecific interaction while the interaction among individuals of different species in a community is termed as interspecific interaction.

Ø Specific terms are applied to interspecific interactions depending upon whether the interaction is beneficial, harmful or neutral to individuals of the species.

Some types of interactions listed by the effects they have on each partner. ‗0‘ is no effect, ‗-‘ is

S. No.

Type of interaction

Species

Effects of interaction

1

2

Negative Interactions

i.

Amensalism

-

0

one species is inhibited while the other

species is unaffected

ii.

Predation

+

-

Predator—prey relationship: one species

(predator) benefits while the second species

(prey) is harmed and inhibited.

iii.

Parasitism

+

-

Beneficial to one species (parasite) and

harmful to the other species (host).

iv.

Competition

-

-

Adversely affects both species

detrimental and ‗+‘ is beneficial.

Possible biological interactions between two species:

Positive Associations

i.

Commensalism

+

0

One species (the commensal) benefits, while

the other species (the host) is neither

harmed nor inhibited

ii.

Mutualism

+

+

Interaction is favourable to both species

Neutral Interactions

i.

Neutralism

0

0 Neither species affects the other

+ = beneficial; - = harmful, 0 = unaffected

Ammensalism:

Ø One species respects or harms the other species without itself being adversely affected or harmed by the presence of the other species.

Ø Organisms that secrete antibiotics and the species that get inhibited by the antibiotics are the examples of amensalism.

Ø For example bread mould fungi pencillium produce pencillin an antibiotic substance which inhibits the growth of a variety of bacteria.

Predation

Ø Predators like leopards, tigers and cheetahs use speed, teeth and claws to hunt and kill their prey.

Ø They keep prey population under control. But for predators, prey species could achieve very high population densities and cause ecosystem instability.

Ø When certain exotic species are introduced into a geographical area, they become invasive and start spreading fast because the invaded land does not have its natural predators.

Ø Predators also help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species.

Ø A wide variety of chemical substances that we extract from plants on a commercial scale (nicotine, caffeine, quinine, strychnine, opium, etc.,) are produced by plants actually as defences against grazers and browsers.

Parasitism

Ø In this type of interaction, one species is harmed and the other benefits.

Ø Parasitism involves parasite usually a small size organism living in or on another living species called the host from which the parasite gets its nourishment and often shelter.

Ø Many organisms like animal, bacteria and viruses are parasites of plants and animals.

Ø Plants like dodder plant (Cuscuta) and mistletoe (Loranthus) are parasites that live on flowering plants.

Ø Tap worm, round worm, malarial parasite, many bacteria, fungi, and viruses are common parasites of humans.

Ø Parasites that feed on the external surface of the host organism are called ectoparasites.

E.g. lice on humans. Many marine fish are infested with ectoparasitic copepods.

Ø The female mosquito is not considered a parasite, although it needs our blood for reproduction. Why? Because it doesn‘t live on the host.

Ø In contrast, endoparasites are those that live inside the host body at different sites (liver, kidney, lungs, red blood cells, etc.).

Ø Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of its host. E.g. cuckoo (koel).

Competition

Ø This is an interaction between two populations in which both species are harmed to some extent.

Ø Competition occurs when two populations or species, both need a vital resource that is in short supply.

Ø The vital resource could be food, water, shelter, nesting site, mates or space.

Ø Such competition can be: interspecific competition-occurring between individuals of two different species occurring in a habitat and intraspecific competition-occurs between individuals of same species.

Ø Intraspecific competition occurs between members of the same species and so it is very intense.

Commensalism

Ø In this relationship one of the species benefits while the other is neither harmed nor benefited.

Ø Some species obtain the benefit of shelter or transport from another species. For example sucker fish, remora often attaches to a shark by means of its sucker which is present on the top side of its head. This helps the remora get protection, a free ride as well as meal from the left over of the shark‘s meal. The shark does not however get any benefit nor is it adversely affected by this association.

Ø Another example of commensalisms is the relationship between trees and epiphytic plants.

Ø Epiphytes live on the surface of other plants like ferns, mosses and orchids and use the surface of trees for support and for obtaining sunlight and moisture. The tree gets no benefit from this relationship nor are they harmed. Cow dung provides food and shelter to dung beetles. The beetles have no effect on the cows.

Ø Another example of commensalism is the interaction between sea anemone that has stinging tentacles and the clown fish that lives among them.

Ø The fish gets protection from predators which stay away from the stinging tentacles. The anemone does not appear to derive any benefit by hosting the clown fish.

Mutualism

Ø This is a close association between two species in which both the species benefit. For example the sea anemone, a cnidarian gets attached to the shell of hermit crabs for benefit of transport and obtaining new food while the anemone provides camouflage and protection by means of its stinging cells to the hermit crab.

Ø However, some mutualisms are so intimate that the interacting species can no longer live without each other as they depend totally on each other to survive. Such close associations are called symbiosis (symbiosis is intense mutualism – E.g. coral and zooxanthellae).

Ø An example of such close mutualistic association is that of termite and their intestinal flagellates. Termites can eat wood but have no enzymes to digest it. However, their intestine contains certain flagellate protists (protozoans) that have the necessary enzymes to digest the cellulose of the wood eaten by termites and convert it into sugar.

Ø The flagellates use some of this sugar for their own metabolism while enough is left for the termite. Both termite and flagellates cannot survive without each other.

Ø Another familiar example of symbiosis is seen in pollination of flowers where flowering plants are cross pollinated by the bees which benefit by getting nectar from the plants and both cannot survive without the other.

Ø Example: in pollination mutualisms, the pollinator gets food (pollen, nectar), and the plant has its pollen transferred to other flowers for cross-fertilization (reproduction). Lichens represent an intimate mutualistic relationship between a fungus and photosynthesizing algae or cyanobacteria.

Ø Similarly, the mycorrhizae are associations between fungi and the roots of higher plants. The fungi help the plant in the absorption of essential nutrients from the soil while the plant in turn provides the fungi with energy-yielding carbohydrates.

Neutralism

Ø Neutralism describes the relationship between two species which do interact but do not affect each other.

Ø True neutralism is extremely unlikely and impossible to prove.

Chemical cycles

Biogeo Chemical Cycling or Nutrient Cycling:

Ø The cycling, at various scales, of minerals and compounds through the ecosystem is known as biogeochemical cycle. The cycles (carbon cycle and nitrogen cycle) involve phases of weathering of rocks, uptake and storage by organisms and return to the pool of the soil, the atmosphere or ocean sediments. The biogeochemistry of carbon has attracted particular attention because of the concern of global warming and greenhouse effects.

Ø Energy flow and nutrient circulation are the major functions of the ecosystem. We have studied about energy flow through trophic levels in the previous posts.

Ø Energy is lost as heat forever in terms of the usefulness of the system. On the other hand, nutrients of food matter never get used up. They can be recycled again and again indefinitely.

Ø Carbon, hydrogen, oxygen, nitrogen and phosphorus as elements and compounds make up 97% of the mass of our bodies and are more than 95% of the mass of all living organisms.

Ø In addition to these, about 15 to 25 other elements are needed in some form for the survival and good health of plants and animals.

Ø These elements or mineral nutrients are always in circulation moving from non-living to living and then back to the non-living components of the ecosystem in a more or less circular fashion. This circular fashion is known as biogeochemical cycling (bio for living; geo for atmosphere).

Ø Among the most important nutrient cycles are the carbon nutrient cycle and the nitrogen nutrient cycle.

Ø There are many other nutrient cycles that are important in ecology, including a large number of trace mineral nutrient cycles.

Nutrient Cycles

Ø Based on the replacement period, a nutrient cycle is referred to as Perfect or Imperfect cycle.

Ø A perfect nutrient cycle is one in which nutrients are replaced as fast as they are utilized. Most gaseous cycles are generally considered as perfect cycles.

Ø In contrast sedimentary cycles are considered relatively imperfect, as some nutrients are lost from the cycle and get locked into sediments and so become unavailable for immediate cycling.

Ø Based on the nature of the reservoir, there are two types of cycles namely-Gaseous Cycle

— where the reservoir is the atmosphere or the hydrosphere — water cycle, carbon cycle, nitrogen cycle, etc. and Sedimentary Cycle — where the reservoir is the earth's crust [elements mostly found in earth‘s crust] — phosphorous cycle, sulphur cycle, calcium cycle, magnesium cycle etc.

Carbon Cycle [Gaseous Cycle]

Ø Carbon is a minor constituent of the atmosphere as compared to oxygen and nitrogen.

Ø However, without carbon dioxide life could not exist because it is vital for the production of carbohydrates through photosynthesis by plants.

Ø It is the element that anchors all organic substances from coal and oil to DNA (deoxyribonudeic acid: the compound that carries genetic information).

Ø Carbon is present in the atmosphere, mainly in the form of carbon dioxide (CO2).

Ø Carbon cycle involves a continuous exchange of carbon between the atmosphere and organisms.

Ø Carbon from the atmosphere moves to green plants by the process of photosynthesis, and then to animals.

Ø By process of respiration and decomposition of dead organic matter it returns back to atmosphere. It is usually a short term cycle.

Ø Some carbon also enters a long term cycle. It accumulates as un-decomposed organic matter in the peaty layers of marshy soil or as insoluble carbonates in bottom sediments of aquatic systems which take a long time to be released.

Ø In deep oceans such carbon can remained buried for millions of years till geological movement may lift these rocks above sea level. These rocks may be exposed to erosion, releasing their carbon dioxide, carbonates and bicarbonates into streams and rivers.

Ø Fossil fuels such as coals, oil and natural gas etc. are organic compounds that were buried before they could be decomposed and were subsequently transformed by time and geological processes into fossil fuels. When they are burned the carbon stored in them is released back into the atmosphere as carbon-dioxide.

Nitrogen Cycle [Gaseous Cycle]

Ø Apart from carbon, hydrogen and oxygen, nitrogen is the most prevalent element in living organisms.

Ø

Nitrogen is a constituent of amino acids, proteins, hormones, chlorophylls and many of the vitamins.

Ø Plants compete with microbes for the limited nitrogen that is available in soil. Thus, nitrogen is a limiting nutrient for both natural and agricultural ecosystems.

Ø Nitrogen exists as two nitrogen atoms (N2) joined by a very strong triple covalent bond

(N ≡ N).

Ø In nature, lightning and ultraviolet radiation provide enough energy to convert nitrogen to nitrogen oxides (NO, NO2, N2O).

Ø Industrial combustions, forest fires, automobile exhausts and power-generating stations are also sources of atmospheric nitrogen oxides.

Nitrogen Fixing – Nitrogen to Ammonia (N2 to NH3)

Ø There is an inexhaustible supply of nitrogen in the atmosphere but the elemental form cannot be used directly by most of the living organisms.

Ø Nitrogen needs to be ‗fixed‘, that is, converted to ammonia, nitrites or nitrates, before it can be taken up by plants.

Ø Nitrogen fixation on earth is accomplished in three different ways:

Ø By microorganisms (bacteria and blue-green algae),

Ø By man using industrial processes (fertilizer factories) and

Ø To a limited extent by atmospheric phenomenon such as thunder and lighting.

Ø Certain microorganisms are capable of fixing atmospheric nitrogen into ammonia (NH3)

and ammonium ions (NH4⁺).

Ø The enzyme, nitrogenase which is capable of nitrogen reduction is present exclusively in prokaryotes. Such microbes are called N2-fixers. These include:

Ø free living nitrogen fixing bacteria

Ø (non-symbiotic nitrogen fixing bacteria or nitrogen fixing soil bacteria) (e.g. aerobic Azotobacter and Beijemickia; anaerobic Clostridium and Rhodospirillum), symbiotic nitrogen fixing bacteria (e.g. Rhizobium) living in association with leguminous plants and non-leguminous root nodule plants and some cyanobacteria (major source of nitrogen fixation in oceans)(blue green algae. E.g. Nostoc, Anabaena, Spirulina etc.).

Leguminous: denoting plants of the pea family (Leguminosae), typically having seeds in pods, distinctive flowers, and root nodules containing nitrogen-fixing bacteria.

Nitrification – Ammonia to Nitrates

Ø Ammonium ions can be directly taken up as a source of nitrogen by some plants.

Ø Others absorb nitrates which are obtained by oxidizing ammonia and ammonium ions.

Ø Ammonia and ammonium ions are oxidized to nitrites or nitrates by two groups of specialized bacteria.

Ø Ammonium ions are first oxidized to nitrite by the bacteria Nitrosomonas and/or

Nitrococcus.

Ø The nitrite is further oxidized to nitrate with the help of the bacterium Nitrobacter.

Ø These steps are called nitrification.

Ø These nitrifying bacteria are chemoautotrophs.

Ø The nitrate thus formed is absorbed by plants and is transported to the leaves.

Ø In leaves, it is reduced to form ammonia that finally forms the amine group of amino acids, which are the building blocks of proteins. These then go through higher trophic levels of the ecosystem.

Ø Nitrification is important in agricultural systems, where fertilizer is often applied as ammonia. Conversion of this ammonia to nitrate increases nitrogen leaching because nitrate is more water-soluble than ammonia.

Ø Nitrification also plays an important role in the removal of nitrogen from municipal wastewater. The conventional removal is nitrification, followed by denitrification.

Ammonification – Urea, Uric Acid to Ammonia

Ø Living organisms produce nitrogenous waste products such as urea and uric acid (organic nitrogen).

Ø These waste products as well as dead remains of organisms are converted back into inorganic ammonia and ammonium ions by the bacteria. This process is called ammonification.

Ø Some of this ammonia volatilizes and re-enters the atmosphere but most of it is converted into nitrate by soil bacteria.

Denitrification – Nitrate to Nitrogen

Ø Nitrate present in the soil is reduced to nitrogen by the process of denitrification.

Ø In the soil as well as oceans there are special denitrifying bacteria (Pseudomonas and Thiobacillus), which convert the nitrates/nitrites to elemental nitrogen. This nitrogen escapes into the atmosphere, thus completing the cycle.

Ø Step 1: N2 Fixing Nitrogen → Ammonia or Ammonium Ions

Ø Step 2: Nitrification Ammonia or Ammonium Ions → Nitrite → Nitrate

Ø Step 3: Ammonification Dead Matter + Animal Waste (Urea, Uric Acid) → Ammonia or Ammonium Ions.

Ø Dead Matter + Animal Waste (Urea, Uric Acid) → Ammonia or Ammonium Ions [most of it escapes into atmosphere. Rest is Nitrified (Step 2) to nitrates]

Ø

Nitrate [some of it is available for plants. Rest is Denitrified (Step 4)]

Ø Step 4: Denitrification Nitrate → Nitrogen.

Ø The amount of nitrogen fixed by man through industrial process has far exceeded the amount fixed by the natural cycle.

Ø As a result Nitrogen has become a pollutant which can disrupt the balance of nitrogen. It may lead to Acid rain, Eutrophication and Harmful Algal Blooms.

Phosphorus Cycle [Sedimentary cycle]

Ø

Phosphorus plays a central role in aquatic ecosystems and water quality.

Ø Unlike carbon and nitrogen, which come primarily from the atmosphere, phosphorus occurs in large amounts as a mineral in phosphate rocks and enters the cycle from erosion and mining activities.

Ø This is the nutrient considered to be the main cause of excessive growth of rooted and free- floating microscopic plants (phytoplankton) in lakes [Eutrophication].

Ø The main storage for phosphorus is in the earth's crust. On land phosphorus is usually found in the form of phosphates.

Ø By the process of weathering and erosion phosphates enter rivers and streams that transport them to the ocean.

Ø In the ocean phosphorus accumulates on continental shelves in the form of insoluble deposits.

Ø After millions of years, the crustal plates rise from the sea floor and expose the phosphates on land.

Ø After more time, weathering will release them from rock and the cycle's geochemical phase begins again.

Sulphur Cycle [Sedimentary cycle]

Ø The sulphur reservoir is in the soil and sediments where it is locked in organic (coal, oil and peat) and inorganic deposits (pyrite rock and sulphur rock) in the form of sulphates, sulphides and organic sulphur.

Ø It is released by weathering of rocks, erosional runoff and decomposition of organic

aquatic ecosystems in salt solution.

Ø The sulphur cycle is mostly sedimentary except two of its compounds – hydrogen sulphide (H2S) and sulphur dioxide (SO2) which add a gaseous component.

Ø Sulphur enters the atmosphere from several sources like volcanic eruptions, combustion of fossil fuels (coal, diesel etc.), from surface of ocean and from gases released by decomposition. Atmospheric hydrogen sulphide also gets oxidized into sulphur dioxide.

Ø Atmospheric sulphur dioxide is carried back to the earth after being dissolved in rainwater as weak sulphuric acid.

Ø Whatever the source, sulphur in the form of sulphates is take up by plants | 9 and incorporated through a series of metabolic processes into sulphur bearing amino acid which is incorporated in the proteins of autotroph tissues. It then passes through the grazing food chain.

Ø Sulphur bound in living organism is carried back to the soil, to the bottom of ponds and lakes and seas through excretion and decomposition of dead organic material.

Chapter 02: Terrestrial Ecosystem

A natural ecosystem is an assemblage of plants and animals which functions as a unit and is capable of maintaining its identity. There are two main categories of ecosystems.

Terrestrial ecosystem: Ecosystems found on land e.g. forest, grasslands, deserts, tundra.

Ø Arctic and Alpine Tundra Biome

Ø Taiga or Boreal Biome [Coniferous forests]

Ø Temperate Deciduous Biome [North Western Europe]

Ø Temperate Rainforest Biome

Ø Sub-Tropical Deciduous Biome in Eastern China, South Eastern USA

Ø Temperate Deciduous Biome [Mediterranean Region]

Ø Tropical Deciduous Biome [Monsoon Climate]

Ø Savanna or Tropical Wet and Dry Biome

Ø Tropical Rain Forest Biome

Ø Steppe or Temperate Grassland Biome

Ø Savanna or Tropical Wet and Dry Biome [Tropical Grasslands]

Ø Tropical and Mid Latitude Desert Biome

Aquatic ecosystem

Ø Plants and animal community found in water bodies. These can be further classified into two sub groups.

Ø Fresh water ecosystems, such as rivers, lakes and ponds.

Ø Marine ecosystems, such as oceans, estuary and mangroves.

Terrestrial Ecosystems or Biomes:

Ø The terrestrial part of the biosphere is divisible into enormous regions called biomes, which are characterized, by distinct climate [precipitation and temperature mainly], vegetation, animal life and general soil type.

Ø No two biomes are alike. The climate determines the boundaries of a biome and abundance of plants and animals found in each one of them. The most important climatic factors are temperature and precipitation.

Tundra Biome: There are two types of tundra – arctic and alpine.

Distribution

Ø Arctic tundra extends as a continuous belt below the polar ice cap and above the tree line (taiga) in the northern hemisphere.

Ø It occupies the northern fringe of Canada, Alaska, European Russia, Siberia and island group of Arctic Ocean.

Ø On the south pole, tundra is very small since most of it is covered by ocean.

Ø Alpine tundra occurs at high mountains above the tree line. E.g. High ranges of Himalayas, Andes, Alps etc.

Temperature

Ø The tundra climate is characterized by a very low mean annual temperature. In mid-winter temperatures are as low as 40 – 50 °C below freezing. Precipitation

Ø Precipitation is mainly in the form of snow and sleet.

Natural Vegetation

Ø There are no trees in the tundra (Ground is frozen). Lowest form of vegetation like mosses, lichens etc. are found here and there.

Ø Coastal lowlands support hardy grasses and the reindeer moss which provide the only pasturage for reindeers.

Ø In the brief summer, berry-bearing bushes and Arctic flowers bloom.

Ø In the summer, birds migrate north to prey on the numerous insects which emerge when the snow thaws.

Ø Insects have short life cycles which are completed during favourable period of the year.

Ø Animals like the reindeer, arctic fox, wolves, musk-ox, polar bear, lemming, arctic hare, arctic willow etc. live in tundra region.

Ø Reptiles and amphibians are almost absent.

Ø Most of the animals have long life e.g. arctic willow has a life span of 150 to 300 years.

Ø They are protected from chillness by the presence of thick cuticle and

epidermal hair or fur.

Ø Mammals of the tundra region have large body size and small tail and ear to avoid the loss of heat from the surface [less surface area = less heat loss = less food required to produce heat].

Taiga or Boreal Biome

Temperature

Ø Summers are brief and warm reaching 20-25 °C whereas winters are long and brutually cold – 30-40 °C below freezing.

Precipitation

Ø Typical annual precipitation ranges from 38 cm to 63 cm.

Ø It is quite well distributed throughout the year, with a summer maxima.

Ø In winter the precipitation is in the form of snow.

Soil: Boreal forest soils are characterized by thin podozols and are rather poor.

Ø This is because the weathering of rocks proceeds slowly in cold environments and because the litter derived from conifer needle (leaf) is decomposed very slowly and is not rich in nutrients. Moreover conifers don not shed their leaves frequently.

Ø Most podzols are poor soils for agriculture due to the sandy portion, resulting in a low level of moisture and nutrients.

Ø Some are sandy and excessively drained. Others have shallow rooting zones and poor drainage due to subsoil cementation.

Ø A low pH (acidic) further compounds issues, along with phosphate deficiencies and aluminium toxicity.

Ø The low pH (acidic) factor is due to excessive leaching of alkaline oriented cations which if present would neutralize the organic acids of the accumulating litter.

Natural Vegetation

Ø The predominant vegetation is evergreen coniferous forest.

Ø Conifers are evergreen plant species such as Spruce, fir and pine trees, etc

Ø The conifers require little moisture are best suited to this type of sub-Arctic climate.

Ø The productivity and community stability of a boreal forest are lower than those of any other forest ecosystem.

Ø Animals found in this region include Siberian tiger, wolverine, lynx, wolf, bear, red fox, squirrel, and amphibians like Hyla, Rana, etc.

Coniferous forests

Ø Unlike the equatorial rain forests, Coniferous forests are of moderate density

and are more uniform. The trees in coniferous forests grow straight and tall.

Ø Almost all conifers are evergreen. There is no annual replacement of new leaves as in deciduous trees.

Ø The same leaf remains on the tree for as long as five years. Food is stored in the

trunks, and the bark is thick to protect the trunk from excessive cold.

Ø Conifers are conical in shape. Their conical shape and sloping branches prevent snow accumulation. It also offers little grip to the winds.

Ø Transpiration can be quite rapid in the warm summer. So, leaves are small, thick, leathery and needle-shaped to check excessive transpiration.

Ø The soils of the coniferous forests are poor. They are excessively leached and very acidic.

Ø Humus content is also low as the _Page evergreen leaves barely fall and the rate of decomposition is slow.

Ø Under-growth is negligible because of the poor soil conditions.

Ø Absence of direct sunlight and the short duration of summer are other contributory factors.

Ø Coniferous forests are also found in regions with high elevation [Example: The forests just below the snowline in Himalayas].

Ø But on very steep slopes where soils are immature or non-existent, even the conifer cannot survive [Example: Southern slopes of Greater Himalayas].

Temperate Deciduous Biome [North Western Europe]

Ø Moderately warm summers and fairly mild winters.

Temperature

Ø The mean annual temperatures are usually between 5° C and 15° C.

Ø Winters are abnormally mild. This is because of the warming effect brought by warm North Atlantic Drift. [Eastern Australian warm current in case of New Zealand]

Precipitation

Rainfall occurs throughout the year with winter maxima.

Ø Adequate rainfall throughout the year.

Seasons

Ø As in other temperate regions there are four distinct seasons.

Ø Winter is the season of cloudy skies, foggy and misty mornings, and many rainy days from the passing depressions. (Trees shed their leaved in winter to prevent snow accumulation and protect themselves from severe cold).

Ø Spring is the driest and the most refreshing season when people emerge from the depressing winter to see everything becoming green again.

Ø This is followed by the long, sunny summer.

Ø Next is the autumn with the roar of gusty winds; and the cycle repeats itself.

Ø This type of climate with its four distinct seasons is something that is conspicuously absent in the tropics. [Rainforest == Only Rainy season, Tropical Monsoon == Summer, Winter and Rainy, Tropical Savanna == Summer (rains) and Winter]

Natural Vegetation

Ø Soils of temperate forests are podozolic and fairly deep.

Ø The natural vegetation of this climatic type is deciduous forest.

Ø The trees shed their leaves in the cold season.

Ø This is an adaptation for protecting themselves against the winter snow and frost.

Ø Shedding begins in autumn, the ‗fall‘ season. Growth begins in spring.

Ø Some of the common species include oak, elm, ash, birch, beech, and poplar.

Ø In the wetter areas grow willows (Light weight cricket bats are made from willows. In India willows are found in Kashmir).

Ø Most animals are the familiar vertebrates and invertebrates.

Temperate Rainforest Biome

Ø Temperate rain forests receive an annual precipitation of 200 cm, mostly due to on shore westerlies.

Ø Precipitation occurs in the form of fog, rain as well as snow. Fog is quite common and is an important source of water.

Distribution

Ø This is a small biome in terms of area covered. The main stretch of this habitat is along the northwestern coast of North America from northern California though southern Alaska. There are also small areas in southern Chile, New Zealand, Australia and a few other places around the world.

Natural Vegetation

Ø Big coniferous trees dominate this habitat, including Douglas fir, Western red cedar, Mountain hemlock, Western hemlock, Sitka spruce and Lodgepole pine.

Ø In addition to the trees, mosses and lichens are very common, often growing as epiphytes.

Ø Grizzly Bears are the common mammals found in Alaska.

Sub-Tropical Deciduous Biome in Eastern China, South Eastern USA

Climate

Ø Characterized by a warm moist summer and a cool, dry winter (one exception: winters are also moist in Natal Type).

Temperature

Ø The mean monthly temperature varies between 4° C and 25° C and is strongly modified by maritime influence.

Precipitation

Ø Rainfall is more than moderate, anything from 60 cm to 150 cm.

Ø There is the fairly uniform distribution of rainfall throughout the year. Natural Vegetation

Ø Supports a luxuriant vegetation.

Ø The lowlands carry both evergreen broad-leaved forests and deciduous trees [hardwood].

Ø On the highlands, are various species of conifers such as pines and cypresses which are important softwoods.

Ø Perennial plant growth is not checked by either a dry season or a cold season.

Steppe or Temperate Grassland Biome

Name of the temperate

grassland

region

Pustaz

Hungary and surrounding areas

Prairies

North America

Pampas

Argentina and Uruguay

Bush-veld [more tropical]

Northern South Africa

High Veld [more temperate]

Southern south Africa

Downs

Southern Australia

Canterbury

New Zealand

Temperature: Climate is continental with extremes of temperature; Temperatures vary greatly between summer and winter.

Precipitation: The average rainfall may be taken as about 45 cm, but this varies according to location from 25 cm to 75 cm.

Natural Vegetation of Steppe Climate

Grasses: Greatest difference from the tropical savanna is that steppes are practically treeless and the grasses are much shorter. Grasses are fresh and nutritious. This is typical of the grass of the wheat-lands in North America, the rich black earth or chernozem areas of Russian Ukraine and the better watered areas of the Asiatic Steppes.

Trees: Polewards, an increase in precipitation gives rise to a transitional zone of wooded steppes where some conifers gradually appear.

Animals: Does not have much animal diversity. Horses are common in Asian Steppes.

Temperate Deciduous Biome [Mediterranean Region]

Ø Parts of the world that have Mediterranean type of climate are characterized by warm, dry summers and cool, moist winters.

Ø Trees with small broad leaves are widely spaced and never very tall.

Ø Regions with adequate rainfall are inhabited by low broad leafed evergreen trees [mostly evergreen oaks].

Ø Fire is an important hazardous factor in this ecosystem and the adaptation of the plants enable them to regenerate quickly after being burnt.

Ø Plants are in a continuous struggle against heat, dry air, excessive evaporation and prolonged droughts.

Ø They are, in short xerophytic [drought tolerant], a word used to describe the drought-resistant plants in an environment deficient in moisture.

Tropical Deciduous Biome [Monsoon Climate]

Ø Unlike equatorial wet climate, monsoon climate is characterized by distinct wet and dry seasons associated with seasonal reversal of winds.

Ø Floods in wet season and droughts in dry season are common.

Ø Usually there are three seasons namely summer, winter and rainy season.

Ø Monthly mean temperatures above 18 °C.

Ø Temperatures range from 30-45° C in summer.

Ø In winters, temperature range is 15-30°

Ø C with mean temperature around 20- 25° C.

Precipitation

Ø Annual mean rainfall ranges from 200-250 cm. In some regions it is around 350 cm Places like Cherrapunji & Mawsynram receive an annual rainfall of about 1000 cm.

Tropical Monsoon Forests

Ø Also known as drought-deciduous forest; dry forest; dry-deciduous forest; tropical deciduous forest.

Ø Teak, neem, bamboos, sal, shisham, sandalwood, khair, mulberry are some of the important species found here.

Savanna or Tropical Wet and Dry Biome

Ø This type of biome has alternate wet and dry seasons similar to monsoon climate but has considerably less annual rainfall.

Ø Also, there is no distinct rainy season like in monsoon climate. [Only two seasons – winter and summer. Rains occur in summer].

Ø Floods and droughts are common.

Ø Vegetation, wildlife and human life are quite different from monsoon climate regions.

Rainfall: Mean annual rainfall ranges from 80 – 160 cm [Rainfall decreases with distance from equator].

Temperature: Mean annual temperature is greater than 18° C. The monthly temperature hovers between 20° C and 32° C for lowland stations.

Natural Vegetation of Savanna Climate

Ø The savanna landscape is typified by tall grass and short trees.

Ø The grasslands are also called as ‗bush-veld‘.

Ø The trees are deciduous, shedding their leaves in the cool, dry season to prevent excessive loss of water through transpiration, e.g. acacias.

Ø Trees usually have broad trunks, with water-storing devices to survive through the prolonged drought.

Ø Many trees are umbrella shaped, exposing only a narrow edge to the strong winds.

Ø In true savanna lands, the grass is tall and coarse, growing 6 to 12 feet high.

Ø The elephant grass may attain a height of even 15 feet.

Ø Grasses appear greenish and well-nourished in the rainy season but turns yellow and dies down in the dry season that follows.

Ø As the rainfall diminishes towards the deserts the savanna merges into thorny scrub.

Animal Life of the Savanna

Ø There are two main groups of animals in the savanna, the grass-eating herbivorous animals and the fleshing-eating carnivorous animals.

Ø The herbivorous include the zebra, antelope, giraffe, deer, gazelle, elephant etc. [most of the National geographic and Animal Planet documentaries on wild animals are shot in savanna regions] and carnivorous animals include the lion, tiger, leopard, hyena, panther, jaguar, jackal etc..

Ø Species of reptiles and mammals including crocodiles, alligators, giant lizards live together with the larger rhinoceros and hippopotamus in rivers and marshy lakes.

Tropical Rain Forest Biome

Ø Also known as ‗The Hot, Wet Equatorial Climate‘, ‗Equatorial Rainforest Climate‘.

Ø The regions are generally referred as ‗Equatorial Rainforests‘, ‗Equatorial Evergreen Forests‘, ‗Tropical Moist Broadleaf Forest‘, ‗Lowland Equatorial Evergreen Rainforest‘.

Temperature

Ø Temperature is uniform throughout the year.

Ø The mean monthly temperatures are always around 27° C with very little variation.

Ø There is no winter. [Typical to Equatorial Rainforest Climate]

Precipitation

Ø Precipitation is heavy and well distributed throughout the year.

Ø Annual average is always above 150 cm. In some regions the annual average may be as high as 250 – 300 cm.

Ø Equatorial Vegetation

Ø High temperature and abundant rainfall support a luxuriant tropical rain forest.

Ø In the Amazon lowlands, the forest is so dense that it is called ‗selvas'. [selvas: A dense tropical rainforest usually having a cloud cover (dense canopy)]

Ø Unlike the temperate regions, the growing season here is all the year round- seeding, flowering, fruiting and decaying do not take place in a seasonal pattern.

Ø The equatorial vegetation comprises a multitude of evergreen trees that yield

tropical hardwood, e.g. mahogany, ebony, dyewoods etc.

Ø In the coastal areas and brackish swamps, mangrove forests thrive.

Ø All plants struggle upwards (most ephiphytes) for sunlight resulting in a peculiar layer arrangement [Canopy].

Desert Biome

Ø Deserts are regions where evaporation exceeds precipitation.

Ø There are mainly two types – hot like the hot deserts of the Saharan type and temperate as are the mid-latitude deserts like the Gobi.

Hot Deserts

Ø They include the biggest Sahara Desert (3.5 million square miles), Great Australian Desert, Arabian Desert, Iranian Desert, Thar Desert, Kalahari and Namib Deserts.

Ø In North America, the desert extends from Mexico into U.S.A. and is called by different names at different places, e.g. the Mohave, Sonoran, Californian and Mexican Deserts.

Ø In South America, the Atacama or Peruvian Desert is the driest of all deserts with less than 2 cm of rainfall annually.

Mid-Latitude Deserts

Ø The temperate deserts are rainless because of either continentality or rain- shadow effect. [Gobi desert is formed due to continentality and Patagonian desert due to rain-shadow effect]

Ø Amongst the mid-latitude deserts, many are found on plateau and are at a considerable distance from the sea. These are Ladakh, The Kyzyl Kum,

Ø Turkestan, Taklimakan and Gobi deserts of Central Asia, drier portions of the Great Basin Desert of the western United States and Patagonian Deserts of Argentina etc..

Ø The Patagonian Desert is more due to its rain-shadow position on the leeward side of the lofty Andes than to continentiality.

Rainfall (Both Hot and Cold deserts)

Ø Deserts, whether hot or mid-latitude have an annual precipitation of less than 25 cm.

Temperature of Hot deserts

Ø

There is no cold season in the hot Page deserts and the average summer _{| 11}

temperature is high around 30°C.

Ø The highest temperature recorded is 57.77° C in 1922 at A1 Azizia, Libya. Desert Vegetation

Ø The predominant vegetation of both hot and mid-latitude deserts is xerophytic

or drought-resistant.

Ø This includes the cacti, thorny bushes, long-rooted wiry grasses and scattered dwarf acacias.

Ø Trees are rare except where there is abundant ground water to support clusters of date palms.

Ø Most desert shrubs have long roots and are well spaced out to gather moisture, and search for ground water. Plants have few or no leaves and the foliage is either waxy, leathery, hairy or needle-shaped to reduce the loss of water through transpiration.

Ø The seeds of many species of grasses and herbs have thick, tough skins to protect them while they lie dormant.

Indian Biomes – Indian Forest Types

Classification of Natural Vegetation of India is primarily based on spatial and annual variations in rainfall. Temperature, soil and topography are also considered.

Annual Rainfall

Type of Vegetation

200 cm or more

Evergreen rain forests

100cm to 200cm

Mansoon deciduous forests

50cm to 100cm

Drier deciduous or tropical

savanna

25cm to 50cm

Dry thorny shrubs (Semi-arid)

Below 25cm

Desert (arid)

Ø Temperature is the major factor in Himalayas and other hilly regions with an elevation of more than 900 metres.

Ø As the temperature falls with altitude in the Himalayan region the vegetal cover changes with altitude from tropical to sub-tropical, temperate and finally alpine.

Ø Soil is an equally determining factor in few regions. Mangrove forests, swamp forests are some of the examples where soil is the major factor.

Ø Topography is responsible for certain minor types e.g. alpine flora, tidal forests, etc..

Ø India's vegetation can be divided into 5 main types and 16 sub-types as given below.

Ø Moist Tropical Forests

o Tropical Wet Evergreen

o Tropical Semi-Evergreen

o Tropical Moist Deciduous

o Littoral and Swamp

Ø Dry Tropical Forest

o Tropical Dry Evergreen

o Tropical Dry Deciduous

o Tropical Thorn

Ø Montane Sub-tropical Forests

o Sub-tropical broad leaved hill

o Sub-tropical moist hill (pine)

o Sub-tropical dry evergreen

Ø Montane Temperate Forests

o Montane Wet Temperate

o Himalayan Moist Temperate

o Himalayan Dry Temperate

Ø Alpine Forests

o Sub-Alpine

o Moist Alpine scrub

o Dry Alpine scrub

Dry Tropical Forests

Ø Tropical Dry Evergreen

Ø Tropical Dry Deciduous

Ø Tropical Thorn

Tropical Dry Evergreen Forests Distribution:Along the coasts of Tamil Nadu.

Climatic Conditions

Ø Annual rainfall of 100 cm [mostly from the north-east monsoon winds in October – December].

Ø Mean annual temperature is about 28°C.

Ø The mean humidity is about 75 per cent.

Ø The growth of evergreen forests in areas of such low rainfall is a bit strange.

Characteristics

Ø Short statured trees, up to 12 m high, with complete canopy.

Ø Bamboos and grasses not conspicuous.

Ø The important species are jamun, tamarind, neem, etc.

Ø Most of the land under these forests has been cleared for agriculture or

casuarina plantations.

Tropical Dry Deciduous Forests Climatic Conditions

Ø Annual rainfall is 100-150 cm.

Characteristics

Ø These are similar to moist deciduous forests and shed their leaves in dry season.

Ø The major difference is that they can grow in areas of comparatively less rainfall.

Ø They represent a transitional type - moist deciduous on the wetter side and thorn forests on the drier side.

Ø They have closed but uneven canopy.

Ø The forests are composed of a mixture of a few species of deciduous trees rising up to a height of 20 metres.

Ø Undergrowth: Enough light reaches the ground to permit the growth of grass and climbers.

Distribution

Ø They occur in an irregular wide strip running from the foot of the Himalayas to Kanniyakumari except in Rajasthan, Western Ghats and West Bengal.

Ø The important species are teak, axle wood, rosewood, common bamboo, red sanders, laurel, satinwood, etc.

Ø Large tracts of this forest have been cleared for agricultural purposes.

Ø These forests have suffer from over grazing, fire, etc.

Tropical Thorn Forests Climatic Conditions

Ø Annual rainfall less than 75 cm.

Ø Humidity is less than 50 per cent.

Ø Mean temperature is 25°-30°C.

Characteristics

The trees are low (6 to 10 metres maximum) and widely scattered. Acacias and euphorbias are prominent.

The Indian wild date is common. Some grasses also grow in the rainy season.

Distribution

Ø Rajasthan, south-western Punjab, western Haryana, Kachchh and neighbouring parts of Saurashtra.

Ø Here they degenerate into desert type in the Thar desert.

Ø Such forests also grow on the leeside of the Western Ghats covering large areas of Maharashtra, Karnataka, Telangana, Andhra Pradesh and Tamil Nadu.

The important species are neem, babul, cactii, etc.

Montane Sub-Tropical Forests

Ø Sub-tropical broad leaved hill

Ø Sub-tropical moist hill (pine)

Ø Sub-tropical dry evergreen

Sub-tropical Broad-leaved Hill Forests Climatic conditions

Ø Mean annual rainfall is 75 cm to 125 cm.

Ø Average annual temperature is 18°-21°C.

Ø Humidity is 80 per cent.

Distribution

Eastern Himalayas to the east of 88°E longitude at altitudes varying from 1000 to 2000 m.

Characteristics

Forests of evergreen species. Commonly found species are evergreen oaks, chestnuts, ash, beech, sals and pines.

Climbers and epiphytes [a plant that grows non-parasitically on a tree or other plant] are common.

These forests are not so distinct in the southern parts of the country. They occur only in the Nilgiri and Palni hills at 1070-1525 metres above sea level.

It is a "stunted rain-forest" and is not so luxuriant as the true tropical evergreen. The higher parts of the Western Ghats such as Mahabaleshwar, the summits of the Satpura and the Maikal Range, highlands of Bastar and Mt. Abu in the Aravali Range carry sub-types of these forests.

Sub-tropical Moist Pine Forests Distribution

Western Himalayas between 73°E and 88°E longitudes at elevations between 1000 to 2000 metres above sea level.

Some hilly regions of Arunachal Pradesh, Manipur, Naga Hills and Khasi Hills.

Timber

Chir or Chil is the most dominant tree which forms pure stands. It provides valuable timber for furniture, boxes and buildings. It is also used for producing resin and turpentine.

Sub-tropical Dry Evergreen Forests Distribution

Found in the Bhabar, the Shiwaliks and the western Himalayas up to about 1000 metres above sea level.

Climatic Conditions

Annual rainfall is 50-100 cm (15 to 25 cm in December-March). The summers are sufficiently hot and winters are very cold.

Characteristics

Low scrub forest with small _{| 19} evergreen stunted trees and shrubs.

Olive, acacia modesta and pistacia are the most predominant species.

Montane Temperate Forests

Montane Wet Temperate

Himalayan Moist Temperate Himalayan Dry Temperate

Montane Wet Temperate Forests Climatic Conditions

Grows at a height of 1800 to 3000 m above sea level Mean annual rainfall is 150 cm to 300 cm

Mean annual temperature is about 11°C to 14°C and the Average relative humidity is over 80 per cent.

Distribution

Higher hills of Tamil Nadu and Kerala, in the Eastern Himalayan region.

Characteristics

These are closed evergreen forests. Trunks have large girth. Branches are clothed with mosses, ferns and other epiphytes. The trees rarely achieve a height of more than 6 metres.

Deodar, Chilauni, Indian chestnut, birch, plum, machilus, cinnamomum, litsea, magnolia, blue pine, oak, hemlock, etc. are important species.

Himalayan Moist Temperate Forests Climatic Conditions

Annual rainfall varies from 150 cm to 250 cm

Such areas are in Ladakh, Lahul, Chamba, Kinnaur, Garhwal and Sikkim.

Distribution

Occurs in the temperate zone of the Himalayas between 1500 and 3300 metres. Cover the entire length of this mountain range in Kashmir, Himachal Pradesh, Uttarakhand, Darjeeling and Sikkim.

Characteristics

Mainly composed of coniferous species.

Species occur in mostly pure strands. Trees are 30 to 50 m high.

Pines, cedars, silver firs, spruce, etc. are most important trees.

They form high but fairly open forest with shrubby undergrowth including oaks, rhododendrons and some bamboos.

Timber

It provides fine wood which is of much use for construction, timber and railway sleepers.

Climatic Conditions

Precipitation is below 100 cm and is mostly in the form of snow.

Characteristics

Coniferous forests with xerophytic shrubs in which deodar, oak, ash, olive, etc are the main trees.

Distribution

Such forests are found in the inner dry ranges of the Himalayas where south-west monsoon is very feeble.

Alpine Forests

Altitudes ranging between 2,900 to 3,500.

These forests can be divided into: (1) sub-alpine; (2) moist alpine scrub and (3) dry alpine scrub.

The sub-alpine forests occur lower alpine scrub and grasslands.

It is a mixture of coniferous and broad-leaved trees in which the coniferous trees attain a height of about 30 m while the broad leaved trees reach only 10 m.

Fir, spruce, rhododendron, etc. are important species.

The moist alpine scrub is a low evergreen dense growth of rhododendron, birch etc. which occurs from 3,000 metres and extends up to snowline.

The dry alpine scrub is the uppermost limit of scrub xerophytic, dwarf shrubs, over 3,500 metres above sea level and found in dry zone. Juniper, honeysuckle, artemesia etc. are important species.

Grassland Ecosystem in India

The grasslands are found where rainfall is about 25-75 cm per year.

Grasslands are generally found in temperate climates [Steppe Grasslands – tree less]. In India, they are found mainly in the high Himalayas.

The rest of India's grasslands are mainly composed of savannas [Tropical grasslands

– trees like khetri, acacias, shrubs, cacti intersperse (scatter among or between other things) here and there].

The major difference between Indian steppes and savannas is that all the forage (food for horses and cattle) in the steppe is provided only during the brief wet season whereas in the savannas forage is largely from grasses that not only grow during the wet season but also from the smaller amount of regrowth in the dry season.

It covers the northern portion of Gujarat, Rajasthan (excluding Aravallis), western Uttar Pradesh, Delhi and Punjab.

The topography is broken up by hill spurs and sand dunes.

Dry sub humid zone

It covers the whole of peninsular India (except Nilgiri).

Moist sub humid zone

It covers the Ganga alluvial plain in Northern India. The topography is level, low lying and ill-drained. Themeda

This extends to the humid montane regions and moist sub-humid areas of Assam, Manipur, West Bengal, Uttar Pradesh, Punjab, Himachal Pradesh and Jammu and Kashmir.

It is derived from the humid forests on account of shifting cultivation and sheep grazing.

Economic importance of grasslands

The livestock wealth plays a crucial role in Indian life. It is a major source of fuel, draught power, nutrition and raw material for village industries.

Grassland biomes are important to maintain the population of livestock such as horse, mule, ass, cow, pig, sheep, goat, buffalo, camel, deer, zebra, etc.

This huge mass of livestock needs fodder for sustenance but there is not enough of it. Only about 13 million hectares in the country are classified as permanent grazing lands. But they exist in a highly degraded state.

Impact of grazing

Due to heavy grazing the mulch cover of the soil reduces and the soil is readily invaded by xerophytic plants.

Increased areas of bare soil creates a new habitat for burrowing animals such as mice, jack-rabbits, gophers, prairie dogs, locusts etc., which render large areas of forage lands sterile.

Soil surface is heavily trampled by cattle leading to pulverized (reduce to fine particles) top soil which is easily washed away by rain.

Soil trampled by cattle in wet season creates puddling which reduce the percolation of water. This leads to quick water runoff and the rate of soil erosion increases.

Reduced percolation also lowers the ground water table leading to water scarcity and drought in dry season.

Wind erosion becomes intense due to bare soil and this slowly leads to desertification of grasslands.

These changes contribute to the reduction of energy flow, and the disruption of the periodicity of the primary producers.

It results in a breakdown of the biogeochemical cycles of water, carbon and nitrogen.

Role of fire

Ø Fire plays an important role in the management of grasslands.

Ø Under moist conditions fire favors grass over trees, whereas in dry conditions fire is often necessary to maintain grasslands against the invasion of desert

shrubs. Burning increases the forage yields (burning of grasses and shrubs adds lot of nutrients to the soil).

Desert Ecosystem

Deserts are formed in regions with less than 25 cm of annual rainfall.

At high altitudes and at greater distance from the equator the deserts are cold and near the equator and at low altitudes in tropics they are hot.

The perennial plant species like bush, cactus, fetrocactus are scattered throughout the desert biomes.

Where soils are suitable, irrigation can convert deserts into some of the most productive agricultural lands.

As the large volume of water passes through the irrigation system, salts may be left behind that will gradually accumulate over the years until they become limiting.

Adaptation

Desert plants conserve water by following methods

They are mostly shrubs.

They have deep roots. Root system spread over large area. Their epidermal layers are made up of thick cuticle.

Leaves are absent or reduced in size.

In some plants leaves are modified into thorns or spines that can carry out photosynthesis.

Leaves and stem are succulent (having thick fleshy leaves or stems adapted to storing water) and water storing.

In some plants even the stem contains chlorophyll for photosynthesis. The seeds germinate only during the short rainy season.

Desert animals

They are fast runners.

They are nocturnal in habit to avoid the sun's heat during day time. They conserve water by excreting concentrated urine.

Animals and birds usually have long legs to keep the body away from the hot ground.

Lizards are mostly insectivorous and can live without drinking water for several days.

Herbivorous animals get sufficient water from the seeds which they eat.

A few species of nocturnal rodents can _Page live in the desert without drinking water.

Indian Desert — Thar desert (hot)

The climate of this region is characterized by excessive drought, the rainfall being scanty and irregular.

The winter rains of northern India rarely penetrate into the region.

The cold season starts from about the middle of November to the middle of March. This season is characterized by extreme variations of temperature and the temperature is frequently below freezing point at night.

During April to June the heat are intense, frequent scorching winds prevail with great desiccating effect.

The relative humidity of the atmosphere is always low.

The climate is hostile to all vegetation, only plants and animals possessing special adaptations being able to establish themselves.

Flora

The proper desert plants may be divided into two main groups. depending directly upon on rain and those depending on the presence of subterranean water.

The first group consists of two types:

the ‗ephemerals‘ and the ‗rain perennials‘.

The ephemerals are delicate annuals, apparently free from any xerophilous adaptations, having slender stems and root-systems and often large flowers.

They appear almost immediately after rain, develop flowers and fruits in an incredibly short time, and die as soon as the surface layer of the soil dries up.

The rain perennials are visible above the ground only during the rainy season, but have a perennial underground stem.

Fauna

It is home to some of India's most magnificent grasslands and sanctuary for a charismatic bird, the Great Indian Bustard.

Among the mammal fauna, the blackbuck, wild ass, chinkara, caracal, sandgrouse and desert fox inhabit the open plains, grasslands, and saline depressions.

The nesting ground of Flamingoes and the only known population of Asiatic wild Ass lies in the remote part of Great Rann, Gujarat.

It is the migration flyway used by cranes and flamingos.

Indian Cold Desert/Temperate Desert

Cold desert of India include areas of Ladakh, Leh and Kargil of Kashmir and Spiti valley of Himachal Pradesh and some parts of northern Uttaranchal and Sikkim.

These arid areas are not affected by the Indian monsoons because they lie in the rain- shadow of the Himalayan mountain systems.

Characterized by extreme cold weather and denuded terrain they are not suitable for plant growth.

Isolated, scattered and over grazed herbaceous shrubs are found. Grazing period is less than 3-4 months.

The flora and fauna is unique to the area. Oak, pine, deodar, birch and rhododendron are the important trees and bushes found there. Major animal include yaks, dwarf cows, and goats.

Characteristics

Severe arid conditions - Dry Atmosphere.

Temperature less than 00 C for most of the period, drops to -500 C during winter. Mean annual rainfall less than 40 cm.

Heavy snow fall occurs between November and march. Soil type - sandy to sandy loam.

Soil pH - neutral to slight alkaline.

Soil nutrient - Poor organic matter content. Soil has low water retention capacity.

Wind erosion is more common.

Narrow growing period, mostly during the summer.

Due to aforesaid extreme cold conditions, growth of vegetation is slow and of stunted nature.

Bio-diversity

Ø Cold desert is the home of highly adaptive, rare endangered fauna, such as Asiatic Ibex, Tibetan Argali, Ladakh Uriyal, Bharal, Tibetan Antelope (chiru), Tibetan Gazelle; Wild Yak, Snow Leopard, Brown Bear, Tibetan Wolf, Wild Dog and Tibetan Wild Ass ('Kiang' a close relative of the Indian wild ass), Woolly hare, Black Necked Crane, etc.

Ø Cold desert comprises of alpine mesophytes [a plant needing only a moderate amount of water] and desert vegetation.

Desertification

It is the destruction of the biological potential of the land which can ultimately lead to desert like conditions.

In arid and semiarid regions, the restoration of the fragile ecosystem is very slow, and issues like deforestation, mining enhances the desertification.

Desertification is a main problem faced by desert adjoining areas, which stretches across parts of Rajasthan, Gujarat, Punjab and Haryana.

Control measures

Ø India as a signatory to United Nations Convention to Combat Desertification (UNCCD) has submitted National Reports to UNCCD since 2000.

Ø The National Action Programme for Combating Desertification was prepared in 2001 to take appropriate action in addressing the problems of desertification.

Ø Some of the major programmes currently implemented that address issues related to land degradation and desertification are Integrated Watershed Management Programme (IWMP), National Afforestation Programme (NAP), National Mission for Green India (GIM), The Mahatma Gandhi National Rural Employment Guarantee Scheme (MGNREGS), Soil Conservation in the Catchment of River Valley Project and Flood Prone River, National Watershed Development Project for Rained Areas (NWDPRA), Desert Development Programme (DDP) Fodder and Feed Development Scheme-component of Grassland Development including Grass Reserves Command Area Development and Water Management (CADWM) programme etc.

India State of Forest Report (ISFR) 2017 released by MoEFCC

The Ministry of Environment, Forest and Climate Change (MoEFCC) has released India State of Forest Report (ISFR) 2017.

It has revealed that total forest and tree cover in India has increased of over 8,021 sq km (about

80.20 million hectare) which is one percent increase from 2015.

Key Findings of ISFR 2017

The increase in the forest cover has been observed as 6,778 sq km and that of tree cover as 1, 243 sq km. The total forest and tree cover is 24.39% of geographical area of the country. The increase in forest cover has been observed in Very Dense Forest (VDF) which absorbs maximum carbon dioxide from the atmosphere. It is followed by increase in forest cover in open forest.

India‘s Global Position

India is ranked 10th in world, with 24.4% of land area under forest and tree cover, even though it accounts for 2.4 % of the world surface area and sustains needs of 17 % of human and 18 % livestock population. India was placed 8th in list of Top Ten nations reporting the greatest annual net gain in forest area.

State-wise break-up

15 states/UTs have above 33% of geographical area under forest cover. About 40% of country‘s forest cover is present in 9 large contiguous patches of the size of 10, 000 sq.km, or more.

7 States/UTs have more than 75% forest cover: Mizoram, Lakshadweep, Andaman & Nicobar Islands, Arunachal Pradesh, Nagaland, Meghalaya and Manipur.

8 States/UTs have forest cover between 33% to 75%: Tripura, Goa, Sikkim, Kerala, Uttarakhand, Dadra & Nagar Haveli, Chhattisgarh and Assam.

Top 5 States with maximum increase in forest cover: Andhra Pradesh (2141 sq km), followed by Karnataka (1101 sq km) and Kerala (1043 sq km), Odisha (885 sq kms) and Telangana (565 sq kms).

Top 5 States with maximum Forest cover (in terms of area): Madhya Pradesh (77,414 sq km) Arunachal Pradesh (66,964 sq km) and Chhattisgarh (55,547 sq km).

Top states with highest Forest cover in terms of percentage geographical area: Lakshadweep with (90.33%), Mizoram (86.27%) and Andaman & Nicobar Islands (81.73%)

Top 5 states where forest cover has decreased: Mizoram (531 sq km), Nagaland (450 sq km), Arunachal Pradesh (190 sq km), Tripura (164 sq km) and Meghalaya (116 sq km). These states are in North Eastern region of the country where total forest cover is very high i.e. more than 70% in each state.

The main reasons for decrease are shifting cultivation, rotational felling, other biotic pressures, diversion of forest lands for developmental activities, submergence of forest cover, agriculture expansion and natural disasters.

Mangrove cover

Mangrove eco-systems are rich in biodiversity and provide number of ecological services. They also play a major role in protecting coastal areas from erosion, tidal storms and tsunamis.

According to ISFR 2017, total mangrove cover stands at 4,921 sq km and has increased by 181 sq kms. 7 out of 12 mangrove states have shown an increase in mangrove cover and none of them show any negative change. Maharashtra (82 sq kms), Andhra Pradesh (37 sq kms) and Gujarat (33 sq kms) are top three gainers in terms of mangrove cover.

Water bodies inside forests

Forests play vital role in water conservation and improve water regime in area. According to ISFR 2017, water bodies inside forest cover have increased by 2,647 sq kms during the last decade. Maharashtra (432 sq kms), Gujarat (428 sq kms), Madhya Pradesh (389 sq kms) are top three states showing increase in water bodies within forest areas. Overall, almost all the states have shown a positive change in water bodies.

Bamboo Cover

The extent of bamboo-bearing area in country is estimated at 15.69 million ha. There has been an increase of 1.73 million ha in bamboo area in comparison to last assessment done in 2011. There is increase of 19 million tonnes in bamboo-growing stock as compared to last assessment done in 2011. The growing stock of bamboo in forest has been estimated to be 189 million tonnes.

Background

The India State of Forest Report 2017 (ISFR 2017) is 15th such report in the series prepared by Forest Survey of India (FSI). The report has been prepared with the help of scientific tools and contains information on forest cover, tree cover, mangrove cover, carbon stock in India‘s forests, growing stock inside and outside the forest areas and forest cover in different patch size classes.

The report for first time contains information on decadal change in water bodies in forest during 2005-2015, forest fire, production of timber from outside forest, state wise carbon stock in different forest types and density classes. FSI has been assessing the forest and tree resources o

Chapter 03: Aquatic Ecosystem

The water-bodies have great diversity in fauna and flora. Aquatic systems have distinct zones characterised with distinct plants, animals and micro-organisms. The variations in the fauna and flora of water-bodies is mainly due to variations in temperature, salinity, thermocline, photic- zone (depth of penetration of light in water), dissolved nutrients, mud, silt and inorganic contents in the water. The main characteristics of aquatic systems have been given in table

Eutrophication – Algal Bloom

Ø Eutrophic water body: it is a a body of water rich in nutrients and so supporting a dense plant population, the decomposition of which kills animal life by depriving it of oxygen.

Ø Eutrophication is the response to the addition of nutrients such as nitrates and

phosphates naturally or artificially, fertilizing the aquatic ecosystem.

Ø Algal blooms are the consequence of Eutrophication.

Ø Eutrophication occurs naturally due to deposition of nutrients [such as in depositional environments] carried by flood waters. It takes over centuries for eutrophication to occur naturally.

Ø Similar nutrient enrichment of lakes at an accelerated rate is caused by human activities [discharge of wastewaters or agricultural runoff, Combustion of fossil fuel (produces gases —nitrogen oxides), growing urban population in the coastal areas) and the consequent phenomenon is known as ‗cultural eutrophication‘. It takes only decades.

Ø Phytoplankton (algae and blue-green bacteria) thrive on the excess nutrients.

Effects of Eutrophication:

Ø Loss of fresh water lakes: Eutrophication eventually creates detritus layer in lakes and produces successively shallower depth of surface water. Eventually the water body is and their population explosion covers almost entire surface layer. This condition is known as algal bloom.

Ø Oxygen in aquatic ecosystem is replenished by photosynthetic aquatic plants. Algal Blooms restrict the penetration of sunlight resulting in death of aquatic plants, and hence restricts the replenishment of oxygen.

Ø The oxygen level is already depleted due to the population explosion of phytoplankton.

Ø Phytoplankton are photosynthetic during day time adding oxygen to aquatic ecosystem. But during nights, they consume far more oxygen as they respire

Algal blooms accentuate the rate of oxygen depletion as the population of phytoplankton is very high.

Ø The primary consumers like small fish are killed due to oxygen deprivation caused by algal blooms.

Ø Death of primary consumers adversely effects the food chain and leads to the destruction of higher life forms. Further, more oxygen is taken up by microorganisms during the decomposition process of dead algae, plants and fishes. Due to reduced oxygen level, the remaining fishes and other aquatic organisms also die. All this eventually leads to degradation of aquatic ecosystem.

Ø The new anaerobic conditions [absence of oxygen] created promote growth of bacteria such as Clostridium botulinum which produces toxins deadly to aquatic organisms, birds and mammals.

Ø Reduced into marsh whose plant community is transformed from an aquatic environment to recognizable terrestrial ecosystem. [Lakes are one of the major sources of fresh water]

Ø New species invasion: Eutrophication may cause the ecosystem competitive by transforming the normal limiting nutrient to abundant level. This cause shifting in species composition of ecosystem.

Ø Toxicity: Some algal blooms when died or eaten, release neuro & hepatotoxins which can kill aquatic organism & pose threat to humans. E.g. Shellfish poisoning.

Ø Loss of coral reefs: Occurs due to decrease in water transparency (increased turbidity).

Ø Affects navigation due to increased turbidity; creates colour (yellow, green, red), smell and water treatment problems; increases biomass of inedible toxic phytoplankton, benthic and epiphytic algae and bloom of gelatinous zooplankton.

Mitigation of Eutrophication

Ø Checking water pollution is the ultimate solution to eutrophication.

Ø Treating Industrial effluents domestic sewage to remove nutrient rich sludge through waste water processing.

Ø Riparian buffer: Interfaces between a flowing body of water and land created near the waterways, farms, roads, etc. in an attempt to filter pollution. Sediments and nutrients are deposited in the buffer zones instead of deposition in water [Wetlands, estuaries are natural riparian buffers].

Ø Increase in efficiency of nitrogen & phosphorous fertilizers and using them in adequate levels.

Ø Nitrogen testing & modeling: N-Testing is a technique to find the optimum amount of fertilizer required for crop plants. It will reduce the amount of nitrogen lost to the surrounding area.

Ø Encouraging organic farming.

Ø Reduction in nitrogen emission from vehicles and power plants.

Harmful Algal Blooms

Ø Algae or phytoplankton are microscopic organisms that can be found naturally in coastal waters.

Ø They are major producers of oxygen and food for many of the animals that live in these waters.

Ø The term "red tide" is a misnomer because blooms are not always red, they are not associated with tides, they are usually not harmful, and some species can be harmful or dangerous at low cell concentrations that do not discolor the water.

Ø Water temperature has also been related to the occurrence of algal blooms, with unusually warm water being conducive to blooms.

Ø A bloom often results in a color change in the water. Algal blooms can be any color, but the most common ones are red or brown. These blooms are commonly referred to as red or brown tides.

Ø Most algal blooms are not harmful but some produce toxins and do affect fish, birds, marine mammals and humans. The toxins may also make the surrounding air difficult to breathe. These are known as Harmful Algal Blooms (HABs).

Ø Harmful Algal Blooms are considered an environmental hazard because these events can make people sick when contaminated shellfish or finfish are eaten, or when people breathe aerosolized HAB toxins near the beach.

Ø HAB events adversely affect commercial and recreational fishing, tourism, and valued habitats, creating a significant impact on local economies and the livelihood of coastal residents.

Red Tide

Ø "Red Tide" is a common name for such a phenomenon where certain phytoplankton species contain pigments and "bloom" such that the human eye perceives the water to be discolored.

Ø Blooms can appear greenish, brown, and even reddish orange depending upon the type of organism, the type of water, and the concentration of the organisms.

Ø Aquatic ecosystems refers to plant and animal communities occurring in water bodies. Aquatic ecosystems are classified on the basis of salinity into following types:

Ø Fresh water ecosystems — Water on land which is continuously cycling and has low salt content (always less than 5 ppt) is known as fresh water. There are two types of fresh water ecosystems: (i) Static or still water (Lentic) ecosystems e.g. pond, lake, bogs and swamps. (ii) Running water (Lotic) ecosystems e.g. springs, mountain brooks, streams and rivers.

Ø Marine ecosystems — the water bodies containing salt concentration equal to or above that of sea water (i.e., 35 ppt or above). Eg: shallow seas and open ocean.

Ø Brackish water ecosystems — these water bodies have salt content in between 5 to 35 ppt. e.g. estuaries, salt marshes, mangrove swamps and forests.

Aquatic Organisms

Ø The aquatic organisms are classified on the basis of their zone of occurrence.

Ø Neuston: These organisms live at the air-water interface e.g. floating plants.

Ø Periphyton: These are organisms which remain attached to stems and leaves of rooted plants or substances emerging above the bottom mud such as sessile algae.

Ø Plankton: Microscopic floating organisms such as algae, diatoms, protozoans and larval forms are called plankton. This group includes both microscopic plants like algae (phytoplankton) and animals like crustaceans and protozoans (zooplankton).

Ø The locomotory power of the planktons is limited so that their distribution is controlled, largely, by currents in the aquatic ecosystems.

Ø Nekton: This group contains powerful swimmers that can overcome the water currents. The animals range in size from the swimming insects to the largest blue whale.

Ø Benthos: The benthic organisms are those found living in the bottom of the water mass.

Factors Limiting the Productivity of Aquatic Habitats

Ø Sunlight and oxygen are the most important limiting factors of the aquatic ecosystems

Sunlight

Ø Sunlight penetration rapidly diminishes as it passes down the column of water.

Ø The depth to which light penetrates a lake determines the extent of plant distribution.

Ø Suspended particulate matters such as clay, silt, phytoplankton, etc. make the water turbid.

Ø Turbidity limits the extent of light penetration and the photosynthetic activity in a significant way.

Ø Based on light penetration and plant distribution they are classified as photic and aphotic zones.

Photic zone

Ø Photic (or "euphotic") zone is the portion that extends from the lake surface down to where the light level is 1% of that at the surface. The depth of this zone depends on the transparency of water.

Ø It is the upper layer of the aquatic ecosystems within which photosynthetic activity is confined. Both photosynthesis and respiration activity takes place.

Aphotic zone

Ø The lower layers of the aquatic ecosystems, where light penetration and plant growth are restricted forms the aphotic zone (profundal zone). Only respiration activity takes place in this zone.

Ø Aphotic zone extends from the end of the photic zones to bottom of the lake.

Dissolved oxygen

Ø In fresh water the average concentration of dissolved oxygen is 10 parts per million or 10 ppm by weight. This is 150 times lower than the concentration of oxygen in an equivalent volume of air.

Ø Oxygen enters the aquatic ecosystem through the air water interface and by the photosynthetic activities of aquatic plants.

Ø Dissolved oxygen escapes the water body through air-water interface and through respiration of organisms (fish, decomposers, zooplanktons, etc.).

Ø The amount of dissolved oxygen retained in water is also influenced by temperature. Oxygen is less soluble in warm water. Warm water also enhances decomposer activity. Therefore, increasing the temperature of a water body increases the rate at which oxygen is depleted from water.

Ø When the dissolved oxygen level falls below 3-5 ppm, many aquatic organisms are likely to die.

Winterkill

Ø An ice layer on the top of a water body can effectively cut off light. Photosynthesis stops but respiration continues in such water body.

Ø If the water body is shallow, the oxygen gets depleted and the fish die. This condition is known as winterkill.

Temperature:

Ø Since water temperatures are less subject to change, the aquatic organisms have narrow temperature tolerance limit.

Ø As a result, even small changes in water temperature are a great threat to the survival of aquatic organisms when compared to the changes in air temperatures in the terrestrial organisms.

Ø Lake Ecology

Ø Any body of standing water, generally large enough in area and depth is known as lake.

Ø The largest lake in the world is lake Superior in North America. Lake Baikal in Siberia is the deepest. Chilka lake of Orissa is largest lake in India.

Ø Three main zones can be differentiated in a lake:-

o Peripheral zone (littoral zone) with shallow water.

o Open water beyond the littoral zone where water is quite deep.

o Benthic zone (bottom) or the floor of the lake.

Ageing of Lakes

Ø Lakes receive their water from surface runoff (sometimes also groundwater discharge) and along with it various chemical substances and mineral matter eroded from the land.

Ø Over periods spanning millennia, ageing occurs as the lakes accumulate mineral and organic matter and gradually, get filled up.

Ø The nutrient-enrichment of the lakes promotes the growth of algae, aquatic plants and various fauna. This process is known as natural ‗eutrophication‘.

Ø Similar nutrient enrichment of lakes at an accelerated rate is caused by human activities (discharge of wastewaters or agricultural runoff) and the consequent ageing phenomenon is known as ‗cultural eutrophication‘.

Ø On the basis of their nutrient content, lakes are categorized as Oligotrophic | 5 (very low nutrients), Mesotrophic (moderate nutrients) and Eutrophic (highly nutrient rich).

Ø Vast majority of lakes in India are either eutrophic or mesotrophic because of the nutrients derived from their surroundings or organic wastes entering them.

Parameter

Oligotrophic

Eutrophic

Oxygen in the bottom layer

Present

Absent

Depth

Tend to be deeper

Tend to be shallower

Water quality for domestic &

Good

Poor

industrial uses

Number of plants and animal

species

Many

fewer

Coral Reefs

Ø Coral reefs are built by and made up of thousands of tiny animals—coral ―polyps‖—that are related to anemones and jellyfish.

Ø Polyps are shallow water organisms which have a soft body covered by a calcareous skeleton. The polyps extract calcium salts from sea water to form these hard skeletons.

Ø The polyps live in colonies fastened to the rocky sea floor.

Ø The tubular skeletons grow upwards and outwards as a cemented calcareous rocky mass, collectively called corals.

Ø When the coral polyps die, they shed their skeleton [coral] on which new polyps grow.

Ø The cycle is repeated for over millions of years leading to accumulation of layers of corals [shallow rock created by these depositions is called reef].

Ø These layers at different stages give rise to various marine landforms. One such important landform is called coral reef.

Ø Coral reefs over a period of time transform or evolve into coral islands (Lakshadweep).

Ø The corals occur in different forms and colours, depending upon the nature of salts or constituents they are made of.

Ø Small marine plants (algae) also deposit calcium carbonate contributing to coral growth.

Coral Reef Relief Features

Fringing reef, barrier reef and atoll (coral islands are formed on atolls) are the most important relief features.

Fringing Reefs (Shore Reefs)

Fringing reefs are reefs that grow directly from a shore. They are located very close to land, and often form a shallow lagoon between the beach and the main body of the reef.

Ø A fringing reef runs as a narrow belt [1-2 km wide]. This type of reef grows from the deep sea bottom with the seaward side sloping steeply into the deep sea. Coral polyps do not extend outwards because of sudden and large increase in depth.

Ø The fringing reef is by far the most common of the three major types of coral reefs, with numerous examples in all major regions of coral reef development.

Ø Fringing reefs can be seen at the New Hebrides Society islands off Australia and off the southern coast of Florida.

What is a lagoon?

Ø A lagoon - as used in the context of coral reef typology - refers to a comparatively wide band of water that lies between the shore and the main area of reef development, and contains at least some deep portions.

Barrier Reefs

Ø Barrier reefs are extensive linear reef complexes that parallel a shore, and are separated from it by lagoon.

Ø This is the largest (in size, not distribution) of the three reefs, runs for hundreds of kilometres and is several kilometres wide. It extends as a broken, irregular ring around the coast or an island, running almost parallel to it.

Ø Barrier reefs are far less common than fringing reefs or atolls, although examples can be found in the tropical Atlantic as well as the Pacific.

Ø The 1200-mile long Great Barrier Reef off the NE coast of Australia is the world's largest example of this reef type.

Ø

The GBR is not actually a single reef as the name implies, but rather a very large complex consisting of many reefs.

Wetland Ecosystem

Land areas of poor surface drainage, such as marshes and swamps are known as wetlands. The wetland ecosystems experience periodic flooding from the adjacent deep-water habitat, and therefore supports plants and animals specifically adapted to such shallow flooding or water logging. Wetlands are shallow lakes, generally less than three meters in depth.

Wetlands include lake littorals (marginal areas between the highest and the lowest water level of the lakes), floodplains, bogs, fens, peat-land, marshy and swampy areas.

Classification of Wetlands

The wetlands may be classified into (i)inland wetland, (ii) coastal wetland. The inland wetland may be natural or man-made. The natural inland wetlands include lakes, ponds, ox-bow lakes, bogs, swamps and marsh, while the man-made wetlands include reservoirs, tanks and waterlogged tracts.

The coastal wetlands include bays, backwaters, creek, estuaries, lagoons, mangroves, salt marsh, tidal-flats. There may be man-made wetlands also along the coasts like salt-pans and aquaculture tracts.

Social Relevance of Wetlands

Wetlands have great significance for humanity and ecology. Some of the important benefits from the wetlands are: (i) they are the habitats of aquatic plants, animals, birds including the migratory species, (ii) areas where sediments and nutrients are filtered from the surface water, (iii) they help in the purification of water, (iv) they mitigate floods, (v) help in the recharge of underground water table, (vi) provide drinking water, fish, fodder and fuel, (vii) help in maintaining biodiversity, and (viii) promote tourism and ecotourism.

The wetlands are however, depleting at a faster pace. The main causes of depletion of wetlands are: (i) rapid growth of population, (ii) encroachment of agriculture on wetlands, (iii) over- grazing, (iv) aquaculture, (v) reclamation, (vi) water-pollution, (vii) dumping grounds for industrial and domestic waste.

Importance of Wetlands

Ø Wetlands are indispensable for the countless benefits or ―ecosystem services‖ that they provide humanity, ranging from freshwater supply, food and building materials, and biodiversity, to flood control, groundwater recharge, and climate change mitigation.

Ø Wetlands are habitat to aquatic flora and fauna, numerous species of native and migratory birds.

Ø Wetlands are an important resource for sustainable tourism.

Ø They carry out water purification, filtration of sediments and nutrients from surface water.

Ø They help in nutrients recycling, groundwater recharging and stabilisation of local climate. Play an important role in flood mitigation by controlling the rate of runoff. Buffer (act as a riparian buffer) shorelines against erosion and pollutants. They act as a genetic reservoir for various species of plants (especially rice).

Reasons for depletion

Ø Excessive pollutants (Industrial effluents, domestic waste, agricultural runoff etc.) are dumped into wetlands beyond the recycling capacity.

Ø Habitat destruction and deforestation create ecological imbalance by altering the population of wetland species.

Ø Conversion of wetlands for agriculture and encroachment by public and mafia.

Ø Overfishing and fish farming (Aquaculture).

Ø Overgrazing in marshy soils.

Ø Removal of sand from beds near seas makes the wetland vulnerable to wave action and tidal bore.

Mitigation

Ø Demarcation of wetlands using the latest technology, proper enforcement of laws and stringent punishments for violators.

Ø Preventing unsustainable aquaculture and cultivation of shellfish.

Ø Treating industrial effluents and water from farmlands before discharging into wetlands.

Ø Utilizing wetlands on a sustainable basis by giving enough time for natural regeneration.

Ø Artificial regeneration for a quick recovery.

Ø Afforestation, weed control, preventing invasive species is the key to wetland conservation.

Ø Preventive measures to stop the introduction of exotic invasive species like water hyacinth.

Ø Soil conservation measures & afforestation.

Ø Preventing grazing in peripherals of wetlands.

Ø Wildlife conservation, sustainable tourism, eco-tourism and sensitizing local populace.

Ø Eutrophication abatement by processing nutrient rich discharge into the water body.

Ø Involving the local population in the conservation of wetlands.

Measures to Protect Wetlands

Ø Ramsar Convention on Wetlands

Ø Ramsar Sites in India

Ø Wetlands International

Ø National Wetlands Conservation Programme (NWCP)

Wetlands International

Ø Wetlands International is a global organisation (NGO) that works to sustain and restore wetlands and their resources for people and biodiversity.

Ø Wetlands International‘s work ranges from research, advocacy and engagement with governments, corporate and international policy fora and conventions.

National Wetlands Conservation Programme (NWCP)

Ø NWCP was implemented in the year 1985-86.

Ø Under the programme, 115 wetlands have been identified by the MoEF which require urgent conservation and management interventions.

Ø Criteria for identification of wetlands of national importance under NWCP are the same as those prescribed under the Ramsar Convention on Wetlands.

Ø The Central Government is responsible for the overall coordination of wetland conservation programmes.

Ø It also provides guidelines, financial & technical assistance to state govt.

Ø Since the land resources belong to them, the State Governments/UT Administration are responsible for the management of wetlands.

Ramsar Convention on Wetlands

Ø International treaty for ―the conservation and sustainable use of wetlands‖.

Ø It is also known as the Convention on Wetlands.

Ø It is named after the city of Ramsar in Iran.

Ø The Convention was signed on 2nd of February 1971.

Ø The 2nd of February each year is World Wetlands Day.

Ø Number of parties to the convention (COP) is170.

Ø At the centre of the Ramsar philosophy is the ―wise use‖ of wetlands.

Ø Wise use: maintenance of ecological character within the context of sustainable development.

Need for Such Convention

Ø Wetlands are indispensable for the countless benefits or ―ecosystem services‖ that they provide ranging from freshwater supply, food and building materials, and biodiversity, flood control, groundwater recharge, and climate change mitigation.

Ø 64% of the world‘s wetlands have disappeared in the last century.

What is wetland

Ø The Convention uses a broad definition of wetlands. It includes all lakes and rivers, underground aquifers, swamps and marshes, wet grasslands, peatland, oases, estuaries, deltas and tidal flats, mangroves and other coastal areas, coral reefs, and all human-made sites such as fish ponds, rice paddies, reservoirs and salt pans.

COP

Ø COP is the policy-making organ of the Convention which adopts decisions (Resolutions and Recommendations) to administer the work of the Convention.

Ø Every three years, representatives of the Contracting Parties meet as the Conference of the Contracting Parties (COP)

Ø COP12 was held in Punta del Este, Uruguay in 2015. COP13 took place in Dubai, United Arab Emirates, in 2018.

Under the Convention, the Contracting Parties commit to:

Ø Work towards the wise use of all their wetlands;

Ø Designate suitable wetlands for the List of Wetlands of International Importance (the

―Ramsar List‖) and ensure their effective management;

Ø Cooperate internationally on trans boundary wetlands, shared wetland systems and shared species.

Ramsar Site

Ø At the time of joining the Convention, each Contracting Party undertakes to designate at least one wetland site for inclusion in the List of Wetlands of International Importance.

Ø The inclusion of a ―Ramsar Site‖ in the List embodies the government‘s commitment to take the steps necessary to ensure that its ecological character is maintained.

Ø There are over 2,300 Ramsar Sites on the territories of 170 Ramsar Contracting Parties across the world.

Ø The countries with the most Sites are the United Kingdom with 170 and Mexico with 142.

Ø Bolivia has the largest area under Ramsar protection.

Transboundary Ramsar Sites

Ø Contracting Parties are designating their new and existing Ramsar Sites as Transboundary Ramsar Sites.

Ø These are ecologically coherent, shared wetlands extending across national borders, which are managed collaboratively.

The Montreux Record

Ø The Montreux Record is a register of wetland sites on the List of Wetlands of International Importance where changes in ecological character have occurred, are occurring, or are likely to occur as a result of technological developments, pollution or other human interference.

Ø It is maintained as part of the Ramsar List.

International Organization Partners

Ø The Ramsar Convention works closely with six organisations known as International Organization Partners (IOPs). These are:

1. Birdlife International

2. International Union for Conservation of Nature (IUCN)

3. International Water Management Institute (IWMI)

4. Wetlands International

5. WWF

6. International Wildfowl & Wetlands Trust (WWT) Other Partners

Ø Convention on Biological Diversity (CBD)

Ø Convention to Combat Desertification (UNCCD),

Ø Convention on the Conservation of Migratory Species of Wild Animals

Ø Convention on Migratory Species (CMS),

Ø World Heritage Convention (WHC) and

Ø Convention on International Trade in Endangered Species (CITES).

Ø Project funding is done by various groups like multilateral development banks, bilateral donors, UN agencies such as UNEP, UNDP, Non-governmental organisations etc.

Criteria for Identification of Wetlands under Ramsar Convention If a wetland

Ø contains a representative, rare, or unique example of a natural or near-natural wetland type.

Ø supports vulnerable, endangered, or critically endangered species; or threatened ecological communities.

Ø supports populations of plant and/or animal species important for maintaining the biological diversity of a particular biogeographic region.

Ø supports plant and/or animal species at a critical stage in their life cycles or provides refuge during adverse conditions.

Ø regularly supports 20,000 or more water birds.

Ø regularly supports 1% of the individuals in a population of one species or subspecies of water birds.

Ø supports a significant proportion of indigenous fish subspecies

Ø is an important source of food for fishes, spawning ground, nursery and/or migration path.

Ø is an important source of food and water resource, increased possibilities for recreation and eco-tourism, etc.

Estuarine Ecosystem

Ø An estuary is a place where a river or a stream opens into the sea (mouth of the river).

Ø It is a partially enclosed coastal area of brackish water (salinity varies between 0-35 ppt) with one or more rivers or streams flowing into it, and with a free connection to the open sea.

Ø At the estuaries, fresh water carrying fertile silt and runoff from the land mixes with the salty sea water.

Ø Estuaries form a transition zone (ecotone) between river environments and maritime environments.

Ø Examples of estuaries are river mouths, coastal bays, tidal marshes, lagoons and deltas.

Ø Estuaries are formed due to rise in sea level, movement of sand and sandbars,glacial processes and tectonic processes.

Ø All the plants and animals in the estuaries are subjected to variations in salinity to which they are adapted (osmoregulation).

Ø Estuaries are greatly influenced by tidal action. They are periodically washed by sea water once or twice a day based on the number of tides.

Ø In some narrow estuaries, tidal bores are significant. Tidal bores cause great damage to the estuarine ecology.

Importance of Estuaries

Ø They are the most productive (more productive than wetlands) water bodies in the world because of the mixing of fresh water and saline water zone where marine organisms of both the ecosystems meet.

Ø Ecotone regions (transitional zones) like mangroves, wetlands, estuaries, grasslands etc. have far greater are ideal locations for the construction of ports and harbours The banks of estuarine channels form a favored location for human settlements, which use the estuaries for fishing and commerce, but nowadays also for dumping civic and industrial waste.

Mangroves

Ø Mangroves represent a characteristic littoral (near the sea shore) forest ecosystem.

Ø These are mostly evergreen forests that grow in sheltered low lying coasts, estuaries, mudflats, tidal creeks backwaters (coastal waters held back on land), marshes and lagoons of tropical and subtropical regions.

Ø Mangroves grow below the high water level of spring tides. The best locations are where abundant silt is brought down by rivers or on the backshore of accreting sandy beaches.

Ø Mangroves are highly productive ecosystems and the trees may vary in height from 8 to 20 m. They protect the shoreline from the effect of cyclones and tsunamis.

Ø They are breeding and spawning ground for many commercially important fishes.

Ø Since mangroves are located between the land and sea they represent the best example of ecotone.

Ø Mangroves are shrubs or small trees that grow in coastal saline or brackish water.

Ø Mangroves are salt tolerant trees, also called halophytes, and are adapted to life in harsh coastal conditions.

Ø Mangrove vegetation facilitates more water loss. Leaves are thick and contain salt secreting glands. Some block absorption of salt at their roots itself.

Ø They contain a complex salt filtration system and complex root system to cope with salt water immersion and wave action.

Ø They are adapted to the low oxygen (anoxic) conditions of waterlogged mud.

Ø They produces pneumatophores (blind roots) to overcome respiration problem in the anaerobic soil conditions.

Ø Mangroves occur worldwide in the tropics and subtropics, mainly between latitudes 25° N and 25° S.

Ø They require high solar radiation to filter saline water through their roots. This explains why mangroves are confined to only tropical and sub-tropical coastal waters.

Ø Mangroves occur in a variety of configurations. Some species (e.g. Rhizophora) send arching prop roots down into the water. While other (e.g.Avicennia) sendvertical

―Pneumatophores‖ or air roots up from the mud.

Ø Adventitious roots which emerged from the main trunk of a tree above ground level are called stilt roots.

Ø Mangroves exhibit Viviparity mode of reproduction. i.e. seeds germinate in the tree itself (before falling to the ground).

Ø This is an adaptive mechanism to overcome the problem of germination in saline water.

Mangroves in India

Ø The mangroves of Sundarbans are the largest single block of tidal holophytic mangroves of the world.

Ø The major species of this dense mangrove forest include Herritiera fames, Rhizophora spp., Bruguiera spp., Ceriops decandra, Sonneratia spp. and Avicennia spp., Nypa fruticans are found along the creeks.

Ø This mangrove forest is famous for the Royal Bengal Tiger and crocodiles. Mangrove areas here are being cleared for agricultural use.

Ø The mangroves of Bhitarkanika (Orissa), which is the second largest in the Indian sub- continent, harbour high concentration of typical mangrove species and high genetic diversity.

Ø Mangrove swamps occur in profusion in the intertidal mudflats on both side of the creeks in the Godavari-Krishna deltaic regions of Andhra Pradesh.

Ø Mangroves of Pichavaram and Vedaranyam are degraded mainly due to construction of aquaculture ponds and salt pans.

Ø On the west coast of India, mangroves, mostly scrubby and degraded occur along the intertidal region of estuaries and creeks in Maharashtra, Goa and Karnataka.

Ø The mangrove vegetation in the coastal zone of Kerala is very sparse and thin.

Ø In Gujarat (north-west coast) mangroves Avicennia marine, Avicennia officinalis and Rhizophora mucronata are found mainly in Gulf of Kachchh and the Kori creek.

Ø Mangroves are of scrubby type with stunted growth, forming narrow, discontinuous patches on soft clayey mud.

Ø The condition of the mangroves is improving especially in the Kori creek region, which is a paleodelta of the Indus river.

Ø In size, mangroves range from bushy stands of dwarf mangroves found in Gulf of Kuchchh, to taller stands found in the Sunderbans.

Ø On the Andaman & Nicobar Islands, the small tidal estuaries, neritic inlets and the lagoons support a dense and diverse undisturbed mangrove flora.

Importance of Mangroves

Ø Mangrove plants have (additional) special roots such as prop roots, pneumatophores which help to impede water flow and thereby enhance the deposition of sediment in areas (where it is already occurring), stabilize the coastal shores, provide breeding ground for fishes.

Ø Mangroves moderate monsoonal tidal floods and reduce inundation of coastal lowlands.

Ø They prevents coastal soil erosion.

Ø They protects coastal lands from tsunami, hurricanes and floods.

Ø Mangroves enhance natural recycling of nutrients.

Ø Mangrove supports numerous flora, avifauna and wild life.

Ø Provide a safe and favorable environment for breeding, spawning, rearing of several fishes.

Ø They supplies woods, fire wood, medicinal plants and edible plants to local people.

Ø They provides numerous employment opportunities to local communities and augments their livelihood.

Threats:

Ø They are destroyed for conversion of area for agricultural purpose, fuel, fodder and, salinization, mining, oil spills, aqua cultural (shrimp farming), use of chemical pesticides & fertilizers, industrial purposes.

Chapter 04: Ozone Depletion

Ozone layer:

Ø The ozone layer is a deep layer in the stratosphere, encircling the Earth, that has large amounts of ozone in it. The layer shields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun.

Ø Interestingly, it is also this ultraviolet radiation that forms the ozone in the first

place. Ozone is a special form of oxygen, made up of three oxygen atoms rather than the usual two oxygen atoms. It usually forms when some type of radiation or electrical discharge separates the two atoms in an oxygen molecule (O₂), which can then individually recombine with other oxygen molecules to form ozone (O₃).

Ø The ozone layer became more widely appreciated by the public when it was realized that certain chemicals mankind manufactures, called chlorofluorocarbons, find their way up into the stratosphere where, through a complex series of chemical reactions, they destroy some of the ozone. As a result of this discovery, an international treaty was signed in 1973 called the Montreal Protocol, and the manufacture of these chemicals was greatly reduced.

Ø The ozone layer has since begun to recover somewhat as a result of these efforts, but there is some science which now suggests that the major volcanic eruptions (mainly El Chichon in 1983 and and Mt. Pinatubo in 1991) which have occurred since we started monitoring ozone with satellites in the late 1970's, could have also contributed to the ozone depletion.

Ø The amount of stratospheric ozone overhead on any given day and at any given location varies quite a bit. Because of vertical circulations of air in both the troposphere and the stratosphere, there can be greater or lesser amounts of ozone protecting you from ultraviolet radiation. Also, living at higher elevations exposes people to more UV radiation than at low elevations.

Ø While stratospheric ozone which protects us from the sun is good, there is also ozone produced near the ground from sunlight interacting with atmospheric pollution in cities that is bad for human health. It causes breathing problems for some people, and usually occurs in the summertime when the pollution over a city builds up during stagnant air conditions associated with high pressure areas.

Ozone Hole – Ozone Depletion

Ø Polar vortex and ozone depletion are two distinct but related phenomena.

Ø Ozone gas is continuously formed by the action of UV rays on molecular oxygen in the stratosphere. Also, ozone is simultaneously degraded into molecular oxygen in the stratosphere.

Ø There should be a balance between production and degradation of ozone in the stratosphere so that there is a continuous layer of ozone.

Ø Of late, the balance has been disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs) [chlorofluorocarbons (CFCs)

Ø are

halocarbons]. There is a steady decline of about 4% in the total volume of ozone in Earth's stratosphere.

Ø Much larger decrease in stratospheric ozone is observed around Earth's polar regions. Halocarbon == a compound in which the hydrogen of a hydrocarbon is replaced by halogens like chlorine, bromine, iodine etc.

Ø Halogen == group of reactive non-metallic elements like fluorine, chlorine, bromine, iodine, and astatine.

Ø The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU).

Ø The ozone measurement instruments and techniques are varied. Some of them are the Dobson spectrometer and the filter ozonometer called M83.

Halogen atoms like chlorine destroy ozone

Ø Photodissociation (under the influence of sunlight) of ozone-depleting substances (ODS) like halocarbon refrigerants (CFCs), halocarbon solvents (Methyl Chloroform, carbon tetrachloride), propellants, and foam-blowing agents (CFCs, HCFCs, carbon tetrachloride and trichloroethane, freons, halons [used in firefighting]) creates free chlorine atoms that destroy ozone.

Ø Bromine containing compounds called halons and HBFCs, i.e. hydrobromo fluorocarbons [both used in fire extinguishers and methyl bromide (a widely used pesticide)] release bromine atoms similar to CFCs that release chlorine atoms.

Ø Each bromine atom destroys hundred times of more ozone molecules than what a chlorine atom does.

Polar Vortex

Ø Polar vortex (circumpolar vortex) is a polar cyclone.

Ø A polar vortex is a large pocket of very cold air, typically the coldest air in the Northern Hemisphere, which sits over the polar region during the winter season.

Ø Polar vortex is closely associated with jet streams [Rossby waves].

Ø It is formed mainly in winter and gets weaker in summer.

Ø It surrounds polar highs and lie within the polar front (boundary separating the temperate and polar air masses).

Polar Stratospheric Clouds (PSCs)

Ø

Extend from 12 km – 22 km above the surface. They are nacreous clouds.

Nacreous clouds

Ø Nacreous clouds, sometimes called mother-of-pearl clouds, are rare clouds.

Ø They are mostly visible within two hours after sunset or before dawn.

Ø They form in frigid regions of the lower stratosphere, some 15 - 25 km (9 -16 mile) high and well above tropospheric clouds.

Ø They are bright even after sunset and before dawn because at those heights there is still sunlight.

Ø

They are seen mostly during winter at high latitudes like Scandinavia, Iceland, Alaska and Northern Canada. Sometimes, however, they occur as far south as England.

Ø PSCs or nacreous clouds contain water, nitric acid and/or sulfuric acid.

Ø They are formed mainly during the event of polar vertex in winter; more intense at south pole.

Ø The Cl-catalyzed ozone depletion is dramatically enhanced in the presence of polar stratospheric clouds (PSCs) [Finally this how polar vortex contributes to

Ø ozone depletion].

Ø A number of naturally occurring substances like Hydrogen oxide (HOx), Methane (CH4), Hydrogen gas (H2), Nitrogen oxides (NOx) aid _Page the process of ozone depletion.

Ø PSCs convert "reservoir" compounds into reactive free radicals (Cl and ClO).

Ø These free radicals deplete ozone as shown in the animation below. So PSC accelerate ozone depletion.

Harmful Effects of Ozone Depletion Effects on Humans

Ø UV rays are highly injurious to living organisms since DNA and proteins of living

organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules.

Ø UV radiation of wavelengths shorter than UV-B, are almost completely absorbed by Earth‘s atmosphere, given that the ozone layer is intact.

Ø But if UV-B manages to reach the troposphere due to ozone depletion, DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers.

Ø In human eye, cornea absorbs UV-B radiation, and a high dose of UV-B causes inflammation of cornea, called snow-blindness cataract, etc. Such exposure may permanently damage the cornea.

In short

Ø Increased susceptibility to skin-cancer

Ø Increase cataract (a medical condition in which the lens of the eye becomes progressively opaque, resulting in blurred vision)

Ø Damage DNA (DNA mutations)

Ø Damage to cornea and causes retinal diseases

Ø Suppresses human immune systems

Effects on terrestrial plants

Psychological and developmental processes of plants are affected by UV-B radiation.

Ø Inhibits photosynthesis

Ø Inhibits metabolism

Ø Represses growth

Ø Destroys cells

Ø Causes DNA mutations

Ø Decline in forest productivity

Effects on aquatic ecosystems

Ø Exposure to solar UV-B radiation has been shown to affect both orientation mechanisms and motility in phytoplankton, resulting in reduced survival rates for plankton population adversely affecting marine food chain.

Ø Marine/freshwater organisms are very sensitive to UV-rays. E.g. Corals

Effects on air quality

Ø Increase in UV-B radiation result in higher photo dissociation rates of key trace gases that control the chemical reactivity of the troposphere.

Ø This can increase both production and destruction of ozone (03) and related oxidants such as hydrogen peroxide (H202), which are known to have adverse effects on human health, terrestrial plants, and outdoor materials.

Ø Changes in the atmospheric concentrations of the hydroxyl radical (OH) may change the atmospheric lifetimes of climatically important gases such as methane (CH4) and the CFC substitutes.

Ø Increased tropospheric reactivity could also lead to increased production of Particulates such as cloud condensation nuclei, from the oxidation and subsequent nucleation of sulphur.

Effects on materials

Ø Accelerate breakdown of paints

Ø Accelerate breakdown of plastics

Ø Affect temperature gradient levels in the atmosphere

Ø Affect atmospheric circulation pattern, climatic changes.

Measures to Prevent Ozone (O3) Layer Depletion

Monitoring of ozone layer is taken up by

Ø World Meteorological Organization (WMO)

Ø World Weather Watch (WWW)

Ø Integrated Global Ocean Services Systems (IGOSS)

Ø Global Climate Observing System (GCOS)

CFC substitutes

Further, use of HCFCs (Hydrochloric fluorocarbons) as a substitute for CFCs is being recommended on temporary basis because HCFCs are relatively less damaging to ozone layer as compared to CFCs, but they are not completely ozone safe.

International Efforts

Recognizing the deleterious effects of ozone depletion, an international treaty, known as the Montreal Protocol, was signed at Montreal (Canada) in 1987 (effective in 1989) to control the

emission of ozone depleting substances.

Vienna Convention for the Protection of the Ozone Layer

Multilateral Environmental Agreement

It was agreed upon at the Vienna Conference of 1985 and entered into force in 1988. It acts as a framework for the international efforts to protect the ozone layer.

However, it does not include legally binding reduction goals for the use of CFCs, the main chemical agents causing ozone depletion. These are laid out in the accompanying Montreal Protocol.

Montreal Protocol

The Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion.

It was agreed in 1987, and entered into force in 1989, followed by a first meeting in Helsinki, May 1989. Since then, it has undergone eight revisions.

As a result of the international agreement, the ozone hole in Antarctica is slowly recovering.

Climate projections indicate that the ozone layer will return to 1980 levels between 2050 and 2070.

It is the single most successful international agreement to date.

The two ozone treaties (Vienna Convention and Montreal Protocol) have been ratified by 197 parties [196 UN states + European Union] making them the first universally ratified treaties in United Nations history.

UN Framework Convention on Climate Change is also ratified by 197 parties.

Pollution:

Chapter 05: Pollution and its different types:

Ø Pollution may be defined as the addition of undesirable material into the environment as a result of human activities. The agents which cause environmental pollution are called pollutants.

Ø A pollutant may be defined as a physical, chemical or biological substance released into the environment which is directly or indirectly harmful to humans and other living organisms.

Ø Pollution may be of the following types: Air pollution, Noise pollution, Water pollution, Soil pollution, Thermal pollution and Radiation pollution.

Ø In order to control environmental pollution, the Government of India has passed the Environment (Protection) Act, 1986 (Bhopal disaster) to protect and improve the quality of our air, water and soil.

Air Pollution:

Ø Air pollution is defined as limited to situation in which the outdoor ambient atmosphere contains materials in concentration, which are harmful to man and his surrounding environment.

Ø Air pollution is one of the most widespread form of pollution all over the world. The main agent of air pollution is wind. Wind gathers and moves pollutants from one area to another, sometimes reducing the

Ø concentration of pollution in one location, while increasing it in another. Such air movement makes the atmosphere‘s condition an international issue. For example, in Europe, the cross-boundary drift of pollution is a major issue because of the close proximity of nations and has led to Europe‘s unification.

Ø As stated above air pollution is caused by natural forces, like volcanic eruptions and forest fire. But human interaction and resource utilization is perhaps taxing the atmosphere‘s capacity to absorb the pollutant. Various human activities, particularly industrial and transport activity lead to the emission of a variety of pollutants to the atmosphere which lead to a number of environmental problems.

Ø The adverse effect of air pollution appears in the form of poor quality of air, acidic precipitation and deposition, and health hazards. The main pollutants of air the carbon dioxide (CO2), carbonic acid (H2SO3), water (H2O), nitric acid (HNO3) sulphuric acid (H2SO4).

Ø

Air pollution may be defined as the presence of any solid, liquid or gaseous substance

including noise and radioactive radiation in the atmosphere in such concentration that may be directly and/or indirectly injurious to humans or other living organisms, property or interferes with the normal environmental processes.

Ø An ever-increasing use of fossil fuels in power plants, industries, transportation, mining, construction of buildings, stone quarries had led to air pollution.

Ø Fossil fuels contain small amounts of nitrogen and sulphur.

Ø Burning of fossil fuels like coal (thermal power plants) and petroleum release different oxides of nitrogen and sulphur into the atmosphere.

Ø These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids drop down with rain, making the rain acidic. This is called acid rain.

Ø Acid rain corrodes the marble monuments like Taj Mahal. This phenomenon is called as Marble cancer.

Ø Other kinds of pollutants are chlorofluorocarbons (CFCs) which are used in refrigerators, air conditioners and as pressurising agents in aerosol sprays. CFCs damage the ozone layer of the atmosphere.

Ø The combustion of fossil fuels also increases the number of suspended particles in the air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons.

Ø Presence of high levels of all these pollutants causes visibility to be lowered, especially in cold weather when water also condenses out of the air. This is known as smog and is a visible indication of air pollution.

Classification of Pollutants:

According to the form in which they persist after release into the environment.

Ø Primary pollutants: These persist in the form in which they are added to the environment

Ø e.g. DDT, plastic.

Ø Secondary Pollutants: These are formed by interaction among the primary pollutants. For example, peroxyacetyl nitrate (PAN) is formed by the interaction of nitrogen oxides and hydrocarbons.

According to their existence in nature

Ø Quantitative Pollutants: These occur in nature and become pollutant when their concentration reaches beyond a threshold level. E.g. carbon dioxide, nitrogen oxide.

Ø Qualitative Pollutants: These do not occur in nature and are man-made. E.g. fungicides, herbicides, DDT etc.

Particulate pollutants

Ø Particulate matter suspended in air are dust and soot released from the industrial

Ø chimneys. Their size ranges from 0.001 to 500 micrometers (µm) in diameter.

Ø Particles less than 10 µm float and move freely with the air current. Particles which are more than 10 µm in diameter settle down. Particles less than 0.02 µm form persistent

Ø aerosols.

Ø Major source of SPM (suspended particulate matter) are vehicles, power plants,

Ø construction activities, oil refinery, railway yard, market place, industries, etc.

Ø According to Central Pollution Control Board (CPCB), particulate size 2.5 µm or less in

Ø diameter (PM 2.5) are responsible for causing the greatest harm to human health.

Ø

These fine particulates can be inhaled deep into the lungs and can cause breathing and respiratory symptoms, irritation, inflammations and pneumoconiosis – a disease of the lungs due to inhalation of dust, characterized by inflammation, coughing, and fibrosis.

Fly ash

Ø Fly ash is ejected mostly by thermal power plants as byproducts of coal burning

operations.

Ø Fly ash pollutes air and water and may cause heavy metal pollution in water bodies.

Ø

Fly ash affects vegetation as a result of its direct deposition on leaf surfaces or indirectly through its deposition on soil.

Ø Fly ash in the air slowly settles on leaves and crops in fields in areas near power plants and lowers the plant yield.

Ø Fly ash is now being used for making bricks and as a land fill material.

Composition

thermal

Ø Fly ash particles are oxide rich and consist of silica, alumina, oxides of iron, calcium, and magnesium and toxic heavy metals like lead, arsenic, cobalt, and copper.

Ø Major oxides are present are Aluminium silicate (in large amounts), silicon dioxide (SiO2) and calcium oxide (CaO).

Advantages

Ø Cement can be replaced by fly ash up to 35%, thus reducing the cost of construction,

· making roads, etc.

Ø Fly ash bricks are light in weight and offer high strength and durability.

Ø Fly ash is a better fill material for road embankments and in concrete roads.

Ø Fly ash can be used in reclamation of wastelands.

Ø Abandoned mines can be filled up with fly ash.

Ø Fly ash can increase the crop yield and it also enhances water holding capacity of the land.

Policy measures of MoEF

Ø The Ministry of Environment and Forests has made it mandatory to use Fly Ash based products in all construction projects, road embankment works and low lying land filling works within 100kms radius of Thermal Power Station and mine filling activities within 50kms radius of Thermal Power Station.

Nanoparticles – NPs

Ø Nanoparticles are particle with dimensions comparable to 1/109 of a meter [1 divided by 100 crores].

Ø Major natural processes that release NPs in the atmosphere are forest fires, volcanic

Ø eruptions, weathering, dust storms from desert etc.

Ø Naturally occurring NPs are quite heterogeneous in size and can be transported over

Ø thousands of kilometres and remain suspended in the air for several days.

Ø Nanotechnology has a global socioeconomic value, with applications ranging from

Ø

electronics to biomedical uses (delivering drugs to target sites).

Ø Man-made NPs are unknowingly or purposely released in the environment during various industrial and mechanical processes.

Effects of Nanoparticles on the environment

Ø After release in the environment, NPs will accumulate in various environmental matrices

Ø such as air, water, soil and sediments including wastewater sludge.

Ø NPs in the environment influences dust cloud formation, environmental hydroxyl radical concentration, ozone depletion, or stratospheric temperature change.

Effect of NNPs on dust cloud formation

Ø NNPs are thought to play an important role in dust-clouds formation after being released

Ø into the environment as they coagulate and form dust cloud.

Ø Dust cloud formation decreases sun light intensity.

Asian brown clouds impact on Himalayan glaciers

Ø Asian brown clouds carry large amounts of soot and black carbon (NPs) which are deposited on the glaciers.

Ø This could lead to higher absorption of the sun's heat and potentially contributing to the increased melting of glaciers.

NPs and ozone depletion

Ø The nanoparticles have greater chemical reactivity. They can result in increased production of reactive oxygen species (ROS), including free radicals like Cl-. Radicals like Cl- destroy ozone. [Explained in ―Ozone Depletion‖]

Ø In chemistry, a radical (a free radical) is an atom, molecule, or ion that has unpaired valence electrons.

Effect of NPs on stratospheric temperature

Ø NPs in the troposphere interact with molecular hydrogen accidentally released from hydrogen fuel cells and other sources.

Ø Molecular hydrogen along with NPs moves up to the stratosphere, resulting in the abundance of water vapour in the stratosphere.

Ø This will cause stratospheric cooling due to formation Stratospheric clouds (mostly ice crystals).

Ø Stratospheric clouds destroys ozone. [Explained in ―Ozone Depletion‖]

Major Gaseous Air Pollutants, Their Sources & Effects:

Prim ary and secondary pollutants:

Ø A primary pollutant is an air pollutant emitted directly from a source.

Ø A secondary pollutant is not directly emitted as such, but forms when other pollutants

Ø (primary pollutants) react in the atmosphere.

Ø Examples of a secondary pollutant include ozone, which is formed when

Ø hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight; NO combines with oxygen in the air; and Acid rain is another example for secondary pollutant. Acid rain is formed when sulfur dioxide or nitrogen oxides react with water. large numbers of automobiles (Nitrogen oxides are the primary emissions).

Ø Nitrogen oxides + Sunlight + Hydrocarbons = Ozone (Ozone in stratosphere it is beneficial, but near the earth‘s surface it results in global warming as it is a greenhouse gas) + PAN

Reactions involved:

Prevention and Control of Air Pollution Indoor Air Pollution:

· Paints, carpets, furniture, etc. in rooms may give out volatile organic compounds (VOCs).

· Use of disinfectants, fumigants, etc. may release hazardous gases.

· In hospitals, pathogens present in waste remain in the air in the form of spores.

· In congested areas, slums and rural areas burning of firewood and biomass results in lot of smoke.

· Children and ladies exposed to smoke may suffer from acute respiratory problems.

Prevention and control of indoor air pollution

· Use of wood and dung cakes should be replaced by cleaner fuels such as biogas, LPG or electricity. The use of solar cookers must be encouraged.

· Those species of trees such as baval (Acacia nilotica) which are least smoky should be used.

· Charcoal is a comparatively cleaner fuel.

· Indoor pollution due to the decay of exposed kitchen waste can be reduced by covering the waste properly.

· Segregation of waste, pre-treatment at the source, sterilisation of rooms will help.

Control of Industrial Pollution

· Industrial pollution can be greatly reduced by:

· use of cleaner fuels such as liquefied natural gas (LNG) in power plants, fertiliser plants etc. which is cheaper in addition to being environmentally friendly.

· employing environment-friendly industrial processes so that emission of pollutants and hazardous waste is minimized.

· installing devices which reduce the release of pollutants.

· Devices like filters, electrostatic precipitators, inertial collectors, scrubbers, gravel bed filters or dry scrubbers are described below:

Filters

· Filters remove particulate matter from the gas stream.

· Baghouse filtration system is the most common one and is made of cotton or synthetic fibres (for low temperatures) or glass cloth fabrics (for higher temperature up to 2900 C).

Electrostatic precipitators (ESP)

· Electrostatic precipitation can remove over 99 per cent particulate matter present in the exhaust.

· The emanating dust is charged with ions, and the ionised particulate matter is collected on an oppositely charged surface.

Working

· An electrostatic precipitator has electrode wires that are maintained at several thousand volts, which produce a corona that releases electrons.

· These electrons attach to dust particles giving them a net negative charge. The collecting plates are grounded (relatively positive charge) and attract the charged dust particles.

· The velocity of air between the plates must be low enough to allow the dust to fall.

· The particles are removed from the collection surface by occasional shaking or by rapping the surface.

· ESPs are used in boilers, furnaces, and many other units of thermal power plants, cement factories, steel plants, etc.

Inertial collectors

· It works on the principle that inertia of SPM (suspended particulate matter) in gas is higher than its solvent and as inertia is a function of the mass of the particulate matter, this device collects heavier particles more efficiently (centrifugation is the technique).

· ‗Cyclone‘ is a common inertial collector used in gas cleaning plants.

Scrubbers

· Scrubbers are wet collectors. They remove aerosols from a stream of gas either by collecting wet particles on a surface followed by their removal or else the particles are wetted by a scrubbing liquid.

· The particles get trapped as they travel from supporting gaseous medium across the interface to the liquid scrubbing medium. (this is just like mucus in trachea trapping dust)

· A scrubber can remove gases like sulphur dioxide.

Catalytic converter

· Catalytic converters, having expensive metals namely platinum- palladium and rhodium as the catalysts, are fitted into automobiles for reducing the emission of poisonous gases.

· As the exhaust passes through the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water , and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas , respectively.

· Motor vehicles equipped with catalytic converter should use unleaded petrol because the lead in the petrol inactivates the catalyst.

Apart from the use of the above mentioned devices, other control measures are:

· increasing the height of chimneys.

· closing industries which pollute the environment.

· shifting of polluting industries away from cities and heavily populated areas.

· development and maintenance of a green belt of adequate width.

Steps Taken to Control Vehicular Pollution:

· The emission standards for automobiles have been set which if followed will reduce the pollution.

· Standards have been set for the durability of catalytic converters which reduce vehicular emission.

· In cities like Delhi, vehicles need to obtain Pollution Under Control (PUC) certificate at regular intervals.

· This ensures that levels of pollutants emitted from vehicles are not beyond the prescribed legal limits.

· The price of diesel is much lower than petrol which promotes the use of diesel. To reduce the emission of sulphur dioxide , sulphur content in diesel has been reduced to 0.05%.

· Earlier lead in the form of tetraethyl lead was added in the petrol to raise octane level for the smooth running of engines. Addition of lead in petrol has been banned to prevent the emission of lead particles.

· Usage of alternative fuels like CNG in public transport vehicles is made mandatory in cities like Delhi. All the buses of Delhi were converted to run on CNG by the end of 2002.

· CNG burns most efficiently, unlike petrol or diesel, in the automobiles and very little of it is left unburnt.

· Moreover, CNG is cheaper than petrol or diesel, cannot be siphoned off by thieves and adulterated like petrol or diesel.

· The main problem with switching over to CNG is the difficulty of laying down pipelines to deliver CNG through distribution points/pumps and ensuring uninterrupted supply.

· Simultaneously parallel steps taken in Delhi for reducing vehicular pollution include phasing out of old vehicles, use of unleaded petrol, use of low-sulphur petrol and diesel, use of catalytic converters in vehicles, application of stringent pollution-level norms for vehicles, etc.

· The Government of India through a new auto fuel policy has laid out a roadmap to cut down vehicular pollution in Indian cities.

· More stringent norms for fuels means steadily reducing the sulphur and aromatics content in petrol and diesel fuels.

· The goal, according to the roadmap, is to reduce sulphur to 50 ppm in petrol and diesel and bring down the level of aromatic hydrocarbons to 35 per cent.

Bharat Stage VI (BS VI) from 2020

· From April 2017, BS IV norms are applicable nationwide.

· October 2018: Supreme Court ordered a ban on the sale of Bharat Stage IV vehicles from April 1, 2020 .

· The central government had announced the April 1, 2020 deadline for adopting Bharat Stage VI emission norms by manufactures.

Bharat Stage (BS) norms

· The BS norms are instituted by the government to regulate the emission of air pollutants from motor vehicles.

· The norms were introduced in 2000.

· The norms limit the release of air pollutants such as nitrogen oxides, carbon monoxide, hydrocarbons, particulate matter (PM) and sulphur oxides from vehicles using internal combustion engines.

· The norms are meant to be adopted by using appropriate fuel and technology.

· As the stage goes up, the control of emissions become stricter.

· BS IV and BS VI norms are based on similar norms in Europe called Euro 4 and Euro 6.

· As decided initially, BS V would have been rolled out by 2021 and BS VI in 2024, but leapfrog to BS VI norms by 2020 (skipping BS V) had to be done because of the carbon footprint obligations.

India‘s UNFCCC commitments (Intended Nationally Determined Contributions)

· Improve the emissions intensity of its GDP by 33 to 35 per cent by 2030 below 2005 levels.

· Increase the share of non-fossil fuels-based electricity to 40 per cent by 2030.

· Enhance forest cover which will absorb 2.5 to 3 billion tonnes of carbon dioxide by 2030.

Differences between BS IV and BS VI

· The extent of sulphur is the major difference between Bharat Stage IV and Bharat Stage VI norms.

· BS-IV fuels contain 50 parts per million (ppm) sulphur ; the BS-VI grade fuel only has 10 ppm sulphur .

· BS VI can bring

o PM in diesel cars down by 80 per cent.

o nitrogen oxides from diesel cars by 70 per cent and in petrol cars by 25 per cent.

· BS VI also makes onboard diagnostics (OBD) mandatory for all vehicles.

· OBD device informs the vehicle owner or the repair technician how efficient the systems in the vehicle are.

· RDE (Real Driving Emission) will be introduced for the first time that will measure the emission in real-world conditions and not just under test conditions.

· Bharat Stage VI norms will also change the way particulate matter is measured. It will now be measured by number standard instead of mass standard.

Impact

· Compliance requires a higher investment in technology to make new vehicles.

· Upgrading vehicles in stock is an additional burden for the manufacturers.

· BS Vl-compliant vehicles will be expensive.

· BS Vl-compliant fuel too will be more expensive.

National Air Quality Monitoring Programme

· Central Pollution Control Board (CPCB) has been executing a nationwide programme of ambient air quality monitoring known as National Air Quality Monitoring Programme (NAMP).

The National Air Quality Monitoring Programme (NAMP) is undertaken

· to determine the status and trends of ambient air quality;

· to ascertain the compliance of NAAQS;

· to identify non-attainment cities;

· to understand the natural process of cleaning in the atmosphere; and

· to undertake preventive and corrective measures.

National Ambient Air Quality Standards (NAAQS)

The NAAQS have been revisited and revised in November 2009 for 12 pollutants, which include

· sulphur dioxide (SO2),

· nitrogen dioxide (NO2),

· particulate matter having micron (PM10),

· particulate matter having a size less than 2.5 microns (PM2.5),

· ozone,

· lead,

· carbon monoxide (CO),

· arsenic,

· nickel,

· benzene,

· ammonia, and

· benzopyrene.

National Air Quality Index (AQI)

· Launched by the Environment Ministry in April 2015.

· Initiative under ‗Swachh Bharat‘.

AQI

· It helps the common man to judge the air quality within his vicinity.

· Index constituted as a part of the Government‘s mission to improve the culture of cleanliness.

Old vs new

· While the earlier measuring index was limited to three indicators, the current measurement index had been made quite comprehensive by the addition of more parameters.

Previously who measured Air pollution

· Central Pollution Control Board along with State Pollution Control Boards have been operating the National Air Monitoring Program (NAMP).

Why is AQI necessary?

· Quality of data from some cities remains weak, and the standards set for pollutants fall short of World Health Organization recommendations.

· The pollution related analysis using a vast number of complex parameters was complicated for the common man to understand.

Categories of air pollution under AQI

· There are six AQI categories, namely Good, Satisfactory, Moderately polluted, Poor, Very Poor, and Severe.

Pollutants considered

· The AQI will consider eight pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb ).

Water Pollution

· Water pollution is the addition/presence of undesirable substances to/in water such as organic, inorganic, biological, radiological, heat, which degrades the quality of water so that it becomes unfit for use‘.

· Natural sources of pollution of water are soil erosion, leaching of minerals from rocks (due to natural solubility and solubility triggered by acid rain) and decaying of organic matter.

Point and non-point sources of pollution

· When pollutants are discharged from a specific location such as a drain pipe carrying industrial effluents discharged directly into a water body it represents point source pollution.

· In contrast, non-point sources include discharge of pollutants from diffused sources or from a larger area such as runoff from agricultural fields, grazing lands, construction sites, abandoned mines and pits, etc.

Causes of Water Pollution Sewage Water

· Sewage water includes discharges from houses and other establishments.

· The sewage contains human and animal excreta, food residues, cleaning agents, detergents, etc.

· Domestic and hospital sewage contain many undesirable pathogenic microorganisms.

Dissolved Oxygen (DO)

· Presence of organic and inorganic wastes in water decreases the dissolved oxygen content of the water.

· Water having DO content below 8.0 mg/L may be considered as contaminated.

· Water having DO content below. 4.0 mg/L is considered to be highly polluted.

· DO content of water is important for the survival of aquatic organisms.

· A number of factors like surface turbulence, photosynthetic activity, O2 consumption by organisms and decomposition of organic matter are the factors which determine the amount of DO present in water.

· The higher amounts of waste increase the rates of decomposition and O2 consumption thereby decreases the DO content of water.

Biological Oxygen Demand (BOD)

· Water pollution by organic wastes is measured in terms of Biochemical Oxygen Demand (BOD).

· BOD is the amount of dissolved oxygen needed by bacteria in decomposing the organic wastes present in water. It is expressed in milligrams of oxygen per litre of water.

· The higher value of BOD indicates low DO content of water .

· Since BOD is limited to biodegradable materials, it is not a reliable method of measuring water pollution.

Chemical oxygen demand (COD)

· Chemical oxygen demand (COD) is a slightly better mode used to measure pollution load in the water.

· COD measures the amount of oxygen in parts per million required to oxidise organic (biodegradable and non-biodegradable) and oxidizable inorganic compounds in the water sample.

Industrial Wastes

· Discharge of wastewater from industries like petroleum, paper manufacturing, metal extraction and processing, chemical manufacturing, etc., that often contain toxic substances, notably, heavy metals (defined as elements with density > 5 g/cm3 such as mercury, cadmium, copper, lead, arsenic ) and a variety of organic compounds.

Agricultural sources

· Agricultural runoff contains dissolved salts such as nitrates, phosphates, ammonia and other nutrients, and toxic metal ions and organic compounds.

· Fertilizers contain major plant nutrients such as nitrogen, phosphorus and potassium .

· Excess fertilisers may reach the groundwater by leaching or may be mixed with surface water.

· Pesticides include insecticides, fungicides, herbicides, etc. They contain a wide range of chemicals such as chlorinated hydrocarbons (CHCs. E.g. DDT, Endosulfan etc.) , organophosphates, metallic salts, carbonates, etc.

· Many of the pesticides are non-degradable, and their residues have a long life.

· Wastes from poultry farms, piggeries and slaughterhouses etc. reach the water though runoff.

Thermal and Radiation Pollution

· Power plants – thermal and nuclear, chemical and other industries use a lot of water for cooling purposes, and the used hot water is discharged into rivers, streams or oceans.

· Discharge of hot water may increase the temperature of the receiving water by 10 to 15

°C above the ambient water temperature. This is thermal pollution.

· Increase in water temperature decreases dissolved oxygen in the water.

· Unlike terrestrial organisms, aquatic organisms are adapted to a uniform steady temperature of the environment. A sudden rise in temperature kills fishes and other aquatic animals.

· One of the best methods of reducing thermal pollution is to store the hot water in cooling ponds, allow the water to cool before releasing into any receiving water body

· Nuclear accidents near water bodies or during natural calamities like tsunami and earthquakes pose the risk of radiation leakage (radiation exposure) into water bodies. E.g. Fukushima Daiichi nuclear disaster.

· Radiation exposure causes mutations in the DNA of marine organisms. If those mutations are not repaired, the cell may turn cancerous.

· Radioactive iodine tends to be absorbed by the thyroid gland and can cause thyroid cancer.

Marine pollution

· Oceans are the ultimate sink of all natural and manmade pollutants.

· The sewerage and garbage of coastal cities are also dumped into the sea.

· The other sources of oceanic pollution are navigational discharge of oil, grease, detergents, sewage, garbage and radioactive wastes, offshore oil mining, oil spills.

Oil Spills

· The most common cause of oil spill is leakage during marine transport and leakage from underground storage tanks.

· An oil spill could occur during offshore oil production as well.

Impact of oil spill on marine life

· Oil being lighter than water covers the water surface as a thin film cutting off oxygen to floating plants and other producers.

· Within hours of an oil spill, the fishes, shellfish, plankton die due to suffocation and metabolic disorders.

· Birds and sea mammals that consume dead fishes and plankton die due to poisoning.

Invasive species

· Plants of water hyacinth are the world‘s most problematic aquatic weed, also called

‗Terror of Bengal ‘.

· They grow abundantly in eutrophic water bodies and lead to an imbalance in the ecosystem.

· They cause havoc by their excessive growth leading to stagnation of polluted water.

Underground water pollution

· In India at many places, the groundwater is threatened with contamination due to seepage from industrial and municipal wastes and effluents, sewage channels and agricultural runoff.

· Pollutants like fluorides, uranium, heavy metals and nutrients like nitrates and phosphates are common in many parts of India.

Nitrates

· Dissolved nitrates commonly contaminate groundwater.

· Excess nitrate in drinking water reacts with haemoglobin to form non- functional methaemoglobin and impairs oxygen transport. This condition is called methemoglobinemia or blue baby syndrome .

Methaemoglobin is a form of the oxygen-carrying metalloprotein haemoglobin. Methaemoglobin cannot bind oxygen, unlike oxyhaemoglobin.

· High level of nitrates may form carcinogens and can accelerate eutrophication in surface waters.

Trace metals

· Include lead, mercury, cadmium, copper, chromium and nickel .

· These metals can be toxic and carcinogenic.

Arsenic

· Seepage of industrial and mine discharges, fly ash ponds of thermal power plants can lead to arsenic in groundwater.

· In India and Bangladesh (Ganges Delta), millions of people are exposed to groundwater contaminated with high levels of arsenic, a highly toxic and dangerous pollutant.

· Chronic exposure to arsenic causes black foot disease . It also causes diarrhoea and also lung and skin cancer.

Fluoride

· Excess fluoride in drinking water causes neuromuscular disorders, gastrointestinal problems, teeth deformity, hardening of bones and stiff and painful joints (skeletal fluorosis).

· Pain in bones and joint and outward bending of legs from the knees is called Knock-Knee syndrome.

· Fluorosis is a common problem in several states of the country due to the intake of high fluoride content water.

Effects of Water Pollution Effects of Water Pollution on Human Health

· Domestic and hospital sewage contain many undesirable pathogenic microorganisms, and its disposal into water without proper treatment may cause an outbreak of serious diseases, such as typhoid, cholera, etc.

· Metals like lead, zinc, arsenic, copper, mercury and cadmium in industrial wastewaters adversely affect humans and other animals.

· Consumption of such arsenic polluted water leads to accumulation of arsenic in the body parts like blood, nails and hairs causing skin lesions, rough skin, dry and thickening of the skin and ultimately skin cancer.

· Mercury compounds in wastewater are converted by bacterial action into extremely toxic methyl mercury, which can cause numbness of limbs, lips and tongue, deafness, blurring of vision and mental derangement.

· Pollution of water bodies by mercury causes Minamata (neurological syndrome) disease in humans.

· Lead causes lead poisoning (Lead interferes with a variety of body processes and is toxic to many organs and tissues).

· The compounds of lead cause anaemia, headache, loss of muscle power and bluish line around the gum.

· Water contaminated with cadmium can cause itai itai disease also called ouch-ouch disease (a painful disease of bones and joints) and cancer of lungs and liver.

Effects of Water Pollution on the Environment

· Micro-organisms involved in biodegradation of organic matter in sewage waste consume a lot of oxygen and make water oxygen deficient killing fish and other aquatic creatures.

· Presence of large amounts of nutrients in water results in algal bloom (excessive growth of planktonic algae. This leads to ageing of lakes.

· A few toxic substances, often present in industrial wastewaters, can undergo biological magnification (Biomagnification) in the aquatic food chain. This phenomenon is well- known for mercury and DDT.

· High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshell and their premature breaking, eventually causing a decline in bird populations.

Effects of Water Pollution on Aquatic Ecosystem

· Polluted water reduces Dissolved Oxygen (DO) content, thereby, eliminates sensitive organisms like plankton, molluscs and fish etc.

· However, a few tolerant species like Tubifex (annelid worm) and some insect larvae may survive in highly polluted water with low DO content. Such species are recognized as indicator species for polluted water.

· Biocides, polychlorinated biphenyls (PCBs) and heavy metals directly eliminate sensitive aquatic organisms.

· Hot waters discharged from industries, when added to water bodies, lowers its DO content.

Eutrophication – Ageing of Lakes

·

Lakes receive their water from surface runoff and along with its various chemical substances and minerals.

· Over periods spanning millennia, ageing occurs as the lakes accumulate mineral and organic matter and gradually, get filled up.

· The nutrient-enrichment of the lakes promotes the growth of algae, aquatic plants and various fauna. This process is known as natural eutrophication.

· Similar nutrient enrichment of lakes at an accelerated rate is caused by human activities and the consequent ageing phenomenon is known as cultural eutrophication.

· On the basis of their nutrient content, lakes are categorized as Oligotrophic (very low nutrients), Mesotrophic (moderate nutrients) and Eutrophic (highly nutrient rich).

· A vast majority of lakes in India are either eutrophic or mesotrophic because of the

Eutrophication and Algal Bloom

· Eutrophic water body: it is a body of water rich in nutrients and so supporting a dense plant population, the decomposition of which kills animal life by depriving it of oxygen.

· Eutrophication is the response to the addition of nutrients such as nitrates and phosphates naturally or artificially, fertilising the aquatic ecosystem.

· Phytoplankton (algae and blue-green bacteria) thrive on the excess nutrients and their population explosion covers almost entire surface layer. This condition is known as algal bloom.

Mechanism

· Phytoplankton are photosynthetic during day time adding oxygen to the aquatic ecosystem.

· But during nights, they consume far more oxygen as they respire aggressively.

· i.e. Algal blooms accentuate the rate of oxygen depletion as the population of phytoplankton is very high.

· The primary consumers like small fish are killed due to oxygen deprivation caused by algal blooms.

· Death of primary consumers adversely affects the food chain.

· Further, more oxygen is taken up by microorganisms during the decomposition process of dead algae, plants and fishes.

· The new anaerobic conditions (absence of oxygen) created to promote the growth of bacteria such as Clostridium botulinum which produces toxins deadly to aquatic organisms, birds and mammals.

· Water temperature has also been related to the occurrence of algal blooms, with unusually warm water being conducive to blooms.

· Algal blooms can be any colours, but the most common ones are red or brown. These blooms are commonly referred to as red or brown tides.

Effects of Eutrophication

· Loss of freshwater lakes: Eutrophication eventually creates detritus layer in lakes and produces successively shallower depth of surface water.

· Eventually, the water body is reduced into marsh whose plant community is transformed from an aquatic environment to a recognizable terrestrial environment.

· Algal Blooms restrict the penetration of sunlight resulting in the death of aquatic plants and hence restricts the replenishment of oxygen.

· New species invasion: Eutrophication may cause the ecosystem competitive by transforming the normal limiting nutrient to abundant level. This cause shifting in species composition of the ecosystem.

· Loss of coral reefs: Occurs due to decrease in water transparency (increased turbidity).

· Affects navigation due to increased turbidity; creates colour (yellow, green, red), smell and water treatment problems; increases biomass of inedible toxic phytoplankton, benthic and epiphytic algae and bloom of gelatinous zooplankton.

Harmful Algal Blooms

· Most algal blooms are not harmful, but some produce toxins. These are known as Harmful Algal Blooms (HABs).

· Toxicity: Some algal blooms when died or eaten, release neuro & hepatotoxins which can kill aquatic organism & pose a threat to humans. E.g. Shellfish poisoning.

· HAB events adversely affect commercial and recreational fishing, tourism, and valued habitats, creating a significant impact on local economies and the livelihood of coastal residents.

Mitigation of Eutrophication

· Treating Industrial effluents domestic sewage to remove nutrient-rich sludge through wastewater processing.

· Riparian buffer: Interfaces between a flowing body of water and land created near the waterways, farms, roads, etc. in an attempt to filter pollution.

· Sediments and nutrients are deposited in the buffer zones instead of deposition in water (Wetlands, estuaries are natural riparian buffers).

· Increase in efficiency of nitrogen & phosphorous fertilisers and using them inadequate levels.

· Nitrogen testing & modelling: N-Testing is a technique to find the optimum amount of fertiliser required for crop plants. It will reduce the amount of nitrogen lost to the surrounding area.

· Encouraging organic farming.

· Reduction in nitrogen emission from vehicles and power plants.

Note: Algal Blooms

· Algae or phytoplankton are microscopic organisms that can be found naturally in coastal waters.

· They are major producers of oxygen and food for many of the animals that live in these waters.

· When environmental conditions are favourable for their development, these cells may multiply rapidly and form high numbers of cells, and this is called an algal bloom.

Marine Pollution

· Marine pollution refers to the emptying of chemicals into the ocean and its harmful effects.

· The potentially toxic chemicals stick to tiny particles and these are taken up by plankton and benthos animals which are deposit or filter feeders concentrating upward within food chains.

· As animal feeds usually have a high fish meal or fish oil content, toxins can be found in consumed food items obtained from livestock and animal husbandry.

· To curb marine pollution and regulate the use of the world‘s oceans by individual States, the nations of the world have come together to form two major conventions:

1. Convention on the Dumping of Wastes at Sea, to be replaced by the 1996 Protocol) and

2. United Nations Convention on Law of the Sea or UNCLOS.

Convention on Dumping of Wastes at Sea

· An inter-governmental conference on the Convention on the Dumping of Wastes at Sea met in London in November 1972 to adopt this instrument, the London Convention.

· The Convention has a global character and is aimed at international control and putting an end to marine pollution.

· The definition of dumping under the Convention relates to deliberate disposal at sea of wastes or other materials from vessels, aircraft, platforms and other man-made structures.

· ‗Dumping‘ here does not cover wastes derived from the exploration and exploitation of sea-bed mineral resources.

· The 1978 amendment dealt with the incineration of wastes at sea.

· Another set of amendments adopted at the same time related to introduction of new procedures for dispute settlement.

· The 1993 amendments banned dumping of low-level radioactive wastes into the seas.

· They phased out the dumping of industrial wastes by 1995 and called for an end to incineration of industrial wastes at sea.

· It is to be noted that dumping of low-level radioactive wastes and industrial wastes as well as incineration of wastes were earlier permitted by the Convention.

· The changing approach, keeping in view the need of the times, led to the adoption of the 1996 Protocol on November 7, 1996.

1996 Protocol

· The Protocol, which became effective in 2006, replaces the 1972 Convention.

· The 1996 Protocol is much more restrictive as compared to the 1972 Convention that allowed dumping provided certain conditions were satisfied.

· 1996 Protocol calls for appropriate preventive measures to be taken when wastes thrown into the sea are likely to cause harm ―even when there is no conclusive evidence to prove a cause relation between inputs and their effects.‖

· The Protocol states that ―the polluter should, in principle, bear the cost of pollution‖.

· The Contracting Parties must ensure that the Protocol does not simply result in pollution being transferred from one part of the environment to another.

· The Protocol prohibits the Contracting Parties from dumping ―wastes or any other matter with the exception of those listed in Annex 1‖.

· Annex 1 includes dredged material; sewage sludge; fish waste from industrial fish processing operations etc. for which the concern is mainly physical impact.

· The Protocol prohibits incineration of wastes at sea (permitted by the 1972 convention but prohibited under the 1993 amendments).

· The Protocol states that ―Contracting Parties shall not allow the export of wastes or other matter to other countries for dumping or incineration at sea‖.

· The International Maritime Organization (IMO) is responsible for Secretariat duties with respect to the Protocol.

2006 Amendments to the Protocol

· Adopted in 2006, the amendments were enforced in 2007.

· The amendments have created a basis in international environment law to regulate carbon capture and storage in subsealed geological formation.

· It is part of the measures being considered to address climate change and ocean acidification like developing low carbon energy forms especially for sources of enormous CO2

· The amendments allow storage of carbon dioxide (CO2) under the seabed but regulate the sequestration of CO2 streams from CO2 capture processes in sub-seabed geological formations.

The United Nations Convention on Law of the Sea

· UNCLOS establishes general obligations for safeguarding the marine environment and protecting freedom of scientific research on the high seas.

· It also creates an innovative legal regime for controlling mineral resource exploitation in deep seabed areas beyond national jurisdiction, through an International Seabed Authority.

· UNCLOS can hold states liable for damage caused by violation of their international obligations to combat pollution of the seas.

Point and non-point sources of pollution

· When pollutants are discharged from a specific location such as a drain pipe carrying industrial effluents discharged directly into a water body it represents point source pollution.

· In contrast, non-point sources include discharge of pollutants from diffused sources or from a larger area such as runoff from agricultural fields, grazing lands, construction sites, abandoned mines and pits, etc.

Water Pollution Control Measures

· Realising the importance of maintaining the cleanliness of the water bodies, the Government of India has passed the Water (Prevention and Control of Pollution) Act, 1974 to safeguard our water resources.

· An ambitious plan to save the river called the Ganga Action Plan was launched in 1985.

· In India, the Central Pollution Control Board (CPCB), an apex body in the field of water quality management, has developed a concept of ―designated best use‖.

· Accordingly, the water body is designated as A, B, C, D, E on the basis of

· pH,

· dissolved oxygen, mg/l

· BOD, (200C) mg/l

· total coliform (MPN/100ml)

· free ammonia mg/l,

· electrical conductivity etc.

· The CPCB, in collaboration with the concerned State Pollution Control Boards, has classified all the water bodies including coastal waters in the country according to their

―designated best uses‖.

· This classification helps the water quality managers and planners to set water quality targets and identify needs and priority for water quality restoration programmes for various water bodies in the country.

· The famous Ganga Action Plan and subsequently the National River Action Plan are results of such exercise.

· Riparian buffers: A riparian buffer is a vegetated area (a ―buffer strip‖) near a stream, usually forested, which helps shade and partially protect a stream from the impact of adjacent land uses.

· Treatment of sewage water and the industrial effluents before releasing it into water bodies. Hot water should be cooled before release from the power plants.

· Excessive use of fertilisers and pesticides should be avoided. Organic farming and efficient use of animal residues as fertilisers can replace chemical fertilizers.

· Water hyacinth (an aquatic weed, invasive species) can purify water by taking some toxic materials and a number of heavy metals from water.

· Oil spills in water can be cleaned with the help of bregoli — a by-product of paper industry resembling sawdust, oil zapper, microorganisms.

· It has been suggested that we should plant eucalyptus trees all along sewage ponds. These trees absorb all surplus wastewater rapidly and release pure water vapour into the atmosphere.

Bioremediation

· Bioremediation is the use of microorganisms (bacteria and fungi) to degrade the environmental contaminants into less toxic forms.

· Microorganisms can be specifically designed for bioremediation using genetic engineering techniques.

In situ bioremediation

· In situ — It involves treatment of the contaminated material at the site.

· Bioventing: supply of air and nutrients through wells to contaminated soil to stimulate the growth of indigenous bacteria.

· Biosparging: Injection of air under pressure below the water table to increase groundwater oxygen concentrations and enhance the rate of biological degradation of contaminants by naturally occurring bacteria.

· Bioaugmentation: Microorganisms are imported to a contaminated site to enhance the degradation process.

Using bioremediation techniques, TERI has developed a mixture of bacteria called ‗Oilzapper and Oilivorous-S‘ which degrades the pollutants of oil-contaminated sites, leaving behind no harmful residues..

Ex situ bioremediation

· Ex situ — involves the removal of the contaminated material to be treated elsewhere.

· Landfarming: contaminated soil is excavated and spread over a prepared bed and periodically tilled until pollutants are degraded. The goal is to stimulate indigenous biodegradative microorganisms and facilitate their aerobic degradation of contaminants.

· Bioreactors: it involves the processing of contaminated solid material (soil, sediment, sludge) or water through an engineered containment system.

· Composting: Composting is nature‘s process of recycling decomposed organic materials into a rich soil known as compost.

Advantages of bioremediation

· Useful for the destruction of a wide variety of contaminants.

· The destruction of target pollutants is possible.

· Less expensive.

· Environment-friendly.

Disadvantages of bioremediation

· Bioremediation is limited to biodegradable compounds. Not all compounds are susceptible to rapid and complete degradation.

· Bioremediation often takes a longer time than other treatment processes.

Phytoremediation

· Phytoremediation is the use of plants to remove contaminants from soil and water.

· Natural phytoremediation is carried out by mangroves, estuarine vegetation and other wetland vegetation.

· Phytoextraction/phytoaccumulation: plants accumulate contaminants into the roots and aboveground shoots or leaves.

Sewage Water Treatment for Domestic Use

· Substances that are removed during the process of drinking water treatment include suspended solids, bacteria, algae, viruses, fungi, and minerals such as iron and manganese.

· The processes involved in removing the contaminants include physical processes such as settling and filtration, chemical processes such as disinfection and coagulation and biological processes such as slow sand filtration.

EcoSan toilets

· Ecological sanitation is a sustainable system for handling human excreta, using dry composting toilets.

· This is a practical, hygienic, efficient and cost-effective solution to human waste disposal.

· With this composting method, human excreta can be recycled into a resource (as natural fertiliser), which reduces the need for chemical fertilisers.

Bio-Toilets

· Designed by Railways along with DRDO. Why Bio Toilets in Rail?

· Direct discharge of human waste from the existing toilet system in trains causes corrosion of the tracks, costing crores to replace the rail tracks.

· The bio-toilets are fitted underneath the lavatories and the human waste discharged into them is acted upon by a particular kind of bacteria that converts it into non- corrosive neutral water.

Terms associated with Bio-Toilets

· Bio-digesters: The term biodigester is used for the shells made up of steel for the anaerobic digestion of human waste.

· Bio tank: The term bio tank is used for the tanks made up of concrete for the anaerobic digestion of human waste.

· Aerobic Bacteria: Aerobic bacteria are those which flourish in the presence of free dissolved oxygen in the wastewater and consume organic matter for their food, and thereby oxidising it to stable end products.

· Anaerobic Bacteria: Anaerobic bacteria flourish in the absence of free dissolved oxygen, and survive by utilizing the bounded molecular oxygen in compounds like nitrates (NO3) and sulphates (SO4) etc. thereby reducing them to stable end products along with evolution of foul-smelling gases like H2S (hydrogen sulphide) , CH4 (methane) .

· Facultative Bacteria: Facultative bacteria can operate either as aerobically or as anaerobically.

· Anaerobic Microbial inoculums: a mixture of different types of bacteria responsible for the breakdown of complex polymers into simple sugars which are further broken down into low chain fatty acids and finally into biogas .

Ground Water

· Note: 22 March is celebrated as the world water day.

· General Assembly of the United Nations proclaimed the period 2005 – 2015 as the International Decade for action on “Water for life”

· The moisture in the soil indicates the presence of water underground.

· If we dig deeper and deeper, we would reach a level where all the space between particles of soil and gaps between rocks are filled with water. The upper limit of this layer is called the water table.

· The water table may be at a depth of less than a metre or may be several metres below the ground. The water found below the water table is called groundwater.

· The process of seeping of water into the ground is called infiltration.

· At places the groundwater is stored between layers of hard rock below the water table. This is known as an aquifer.

· The rainwater can be used to recharge the groundwater. This is referred to as water harvesting.

· Mahatma Gandhi said: “No one need to wait for anyone else to adopt a humane and enlightened course of action.”

Groundwater Contaminants and Their Effects Nitrates

· Dissolved nitrates commonly contaminate groundwater.

· Excess nitrate in drinking water reacts with hemoglobin to form non-functional methaemoglobin, and impairs oxygen transport. This condition is called methaemoglobinemia or blue baby syndrome.

· Note:Methemoglobin is a form of the oxygen-carrying metalloprotein hemoglobin. Methemoglobin cannot bind oxygen, unlike oxyhemoglobin.

· High level of nitrates may form carcinogens and can accelerate eutrophication in surface waters.

Pathogens

· Poor hygiene of wells may cause pathogenic contamination. Water seepage from solid waste dumps and municipal drains may also cause pathogenic contamination.

· Trace metals Include lead, mercury, cadmium, copper, chromium and nickel. These metals can be toxic and carcinogenic.

Arsenic

· Seepage of industrial and mine discharges, fly ash ponds of thermal power plants can lead to metals in groundwater.

· In India and Bangladesh [Ganges Delta], millions of people are exposed to groundwater contaminated with high levels of arsenic, a highly toxic and dangerous pollutant.

· Chronic exposure to arsenic causes black foot disease. It also causes diarrhoea, peripheral neuritis, hyperkeratosis and also lung and skin cancer.

Organic compounds

· Seepage of agricultural runoff loaded with organic compounds like pesticides and may cause pesticide pollution of ground water.

Fluoride

· Excess fluoride in drinking water causes neuromuscular disorders, gastro-intestinal problems, teeth deformity, hardening of bones and stiff and painful joints (skeletal fluorosis).

· Fluorisis is a common problem in several states of the country due to intake of high fluoride content water.

· Fluorides cause dental fluorisis, stiffness of joints (particularly spinal cord) causing humped back.

· Pain in bones and joint and outward bending of legs from the knees is called Knock-Knee syndrome.

· High concentration of fluoride ions is present in drinking water in 13 states of India. The maximum level of fluoride, which the human body can tolerate is 1.5 parts per million (mg/L of water). Long term ingestion of fluoride ions causes fluorosis.

Major Water Issues Of India Water scarcity

· Due to un-even distribution of rainfall in time and space and ever-increasing demand of water for agricultural, industrial and domestic activities, the water resources are over- exploited. This is resulting in shrinking or even drying up of many water bodies for considerable periods in a year.

· Reducing demands by optimum use, minimization of wastage, efforts to reduce the percolation and evaporation losses, conservation efforts in domestic uses, groundwater recharging, rain water harvesting, afforestation, recycling and reuse are important to combat this problem.

Pathogenic pollution

· Water borne diseases are the most important water quality issues in India. This is mainly due to inadequate arrangements for transport and treatment of wastewaters.

Oxygen depletion

· Eutrophication [oxygen depletion due to algal blooms] is a common problem in most of the India lakes and rivers due to discharge of untreated sewage and industrial effluents.

Salinity

· There are number of cases where salinity is increasing in both surface water and groundwater.

· The increase in groundwater salinity is mainly due to increased irrigation activities or sea water intrusion in coastal areas.

Toxic pollution

· Due to discharge of toxic effluents from many industries and increased use of chemicals in agriculture and their subsequent contribution to the water bodies, many water bodies in the country are polluted due to presence of toxic substances.

Ecological health

· A large number of areas in our aquatic environment support rare species of aquatic and amphibious plants and animals and are, therefore, ecologically very sensitive. They need special protection.

Water Conservation and Management

· Primary source of water in India is south-west and north-east monsoons. Monsoon, however, is erratic and amount of rain fall is highly variable in different parts of our country. Hence, surface runoff needs be conserved.

Contour farming

· Contour farming is an example of harvesting technique involving water and moisture control at a very simple level.

· It often consists of rows of rocks placed along the contour of steps. Runoff captured by these barriers also allows for retention of soil, thereby serving as erosion control measure on gentle slopes.

· This technique is especially suitable for areas having rainfall of considerable intensity, spread over large part i.e. in Himalayan area, north east states and Andaman and Nicobar Islands.

· In areas where rainfall is scanty and for a short duration, it is worth attempting these techniques, which will induce surface runoff, which can then be stored.

Ground water conservation Artificial recharge

· Increasing the surface area for percolation, percolation tank construction etc. are some artificial recharge methods.

Catchment area protection (CAP):

· It helps in withholding runoff water albeit temporarily by a check bund constructed across the streams in hilly terrains to delay the run off so that greater time is available for water to seep underground.

· Such methods are in use in north-east states, in hilly areas of tribal belts. This technique also helps in soil conservation. Afforestation in the catchment area is also adopted for water and soil conservation.

Inter-basin transfer of water:

· Western and peninsular regions have comparatively low water resources/cultivable land ratio. Northern and eastern region which are drained by Ganga and Brahmaputra have substantial water resources.

· Hence, the scheme of diverting water from region with surplus water to water deficit region can be adopted.

· Ganga-Cauvery link would enable the transfer of vast quantities of Ganga basin flood water running out to sea, to west and south west India.

· The transfer of the surplus Ganga water would make up for the periodical shortage in Son, Narmada, Godavari, Krishna and Cauvery.

Adoption of drip sprinkler irrigation

·

Surface irrigation methods leads to water loss due to evaporation and percolation.

· Drip irrigation is an efficient method of irrigation in which a limited area near the plant is irrigated by dripping water. This method is particularly useful in row crop.

· Similarly sprinkler method is also suitable for such water scarce areas. About 80% water consumption can be reduced by this method, whereas the drip irrigation can reduce water consumption by 50 to 70 %.

Management of growing pattern of crops:

In water scarce areas, the crop selection should be based on efficiency of the crop to utilize the water. Some of the plants suitable for water scarce areas are:

· plants with shorter growth period;

· high yielding plants that require no increase in water supply;

· Plants with deep and well trenched roots and plants which cannot tolerate surface irrigation.

Selection of crop varieties

· Crop performance and yield are the results of genotype expression as modulated by continuous interactions with the environment.

· Generally, the new varieties of crop do not require more water than the older ones. However, they require timely supply of water because their productivity is high.

· Frequent light irrigation is more conductive than heavy irrigation at large intervals for obtaining high yields.

Nutritional management

· Potassium plays a major role under stress conditions. It improves the tissue water potential by osmoregulation, ultimately increasing the water use efficiency. Experiments conducted at the Water Technology Centre, Coimbatore, indicated that foliar application of 0.5% potassium chloride can reduce the moisture stress in soyabean, sorghum and groundnut.

Recycling of water

· The wastewater from industrial or domestic sources can be used after proper treatment, for irrigation, recharging ground water, and even for industrial or municipal use. If agricultural lands are available close to cities, municipal waste water can be easily used for irrigation.

Reuse of wastewater:

· Wastewater contains lots of nutrients. Its use for irrigation saves these nutrients. It improves the productivity of crops and soil fertility.

· Wastewater is a resource rather than a waste since it contains appreciable amount of nitrogen, phosphorus and potash.

· Stabilization ponds can be used for fish aquaculture. The effluent can also be used for cultivation of short-term and long term, ornamental, commercial and fodder crops.

· The potential applications of reusing of treated wastewater are in the following fields or areas:

o Agricultural use through irrigation of crops as well as for improving river amenity;

o Industrial cooling especially in large industrial enterprises;

o Reuse in municipal public areas such as watering lawns, parks, play grounds and trees;

o Flushing toilets in hotels and residential districts;

o Reuse of the treated wastewater for urban landscape purposes.

o Treated waste water can also be used for groundwater recharging.

Grey water reuse

· Grey water is defined as untreated household wastewater, which has not come into contact with toilet waste. It can originate from the shower, bath, bathroom, washing

basin, clothes washing machine and laundry trough. Grey water can be used in agriculture and many industries.

Reduce the loss of water due to evaporation

· The methods that reduce evaporation from water bodies are - installing wind breaks, reducing energy available for evaporation, constructing artificial aquifers, minimizing exposed surface through reservoir regulation, reducing ratio of area/volume of water bodies, locating reservoirs at higher altitudes and applying monomolecular firms.

· There are numerous methods to reduce losses due to evaporation and to improve soil moisture. Some of them are listed below:

· Mulching i.e. the application of organic or inorganic materials such as plant debris, compost, etc., slows down the surface run-off, improves soil moisture, reduces evaporation losses and improves soil fertility.

· Soil covered by crops, slow down run-off and minimize evaporation losses, hence, fields should not be left bare for long periods of time.

· Ploughing helps to move the soil around. As a consequence it retains more water thereby reducing evaporation.

· Shelter belt of trees and bushes along the edge of agricultural fields slow down the wind speed and reduce evaporation and erosion.

· Planting of trees, grass, and bushes breaks the force of rain and helps rainwater penetrate the soil.

· Fog and dew contain substantial amounts of water that can be used directly by adapted plant species. Artificial surfaces such as netting-surface traps or polythene sheets can be exposed to fog and dew; the resulting water can be used for crops.

· Contour farming is adopted in hilly areas and in lowland areas for paddy fields. Farmers recognize the efficiently of contour based systems for conserving soil and water.

· Salt-resistant varieties of crops have been also developed recently. Because these grow in saline areas, overall agricultural productivity is increased without making additional demands on fresh water sources. Thus, this is a good water conservation strategy.

· Desalination technologies such as distillation, electro-dialysis and reverse osmosis are available.

Water Treatment for Domestic Use

· Substances that are removed during the process of drinking water treatment include suspended solids, bacteria, algae, viruses, fungi, and minerals such as iron and manganese.

· The processes involved in removing the contaminants include physical processes such as settling and filtration, chemical processes such as disinfection and coagulation and ological processes such as slow sand filtration.

Watershed Management

· Watershed is an area that contributes water to a stream or a water body through run-off or underground path. That is the region from which surface water draws into a river, a lake, wet land or other body of water is called its watershed or drainage basin.

· Watershed management is a technique for conservation of water and soil in a watershed.

· The presence of water in soil is essential for the growth of plants and vegetation. Forests and their associated soils and litter layers are excellent filters as well as sponges, and water that passes through this system is relatively pure.

· Various kinds of forest disturbances can speed up the movement of water from the system and in effect, reduce the filtering action.

· In mountainous terrain the forests play a prominent role in prevention of soil erosion.

· Erosion threat can be tackled by the maintenance of continual cover. Ideally, this is achieved by single stem harvesting; only one tree is felled at any one point, and the small gap so created is soon sealed by the outward growth of its neighbors.

· Despite the uncertain balance of water gain and loss, forests offer the most desirable cover for water management strategies.

· In contrast to the rapid flows of short duration characteristics of sparsely vegetated land water yields are gradual, reliable and uniform in forests. Deforested land sheds water swiftly, causing sudden rises in the rivers below.

· Over a large river system, such as that of the Ganga and the Yamuna, forests are a definite advantage since they lessen the risk of floods. They also provide conditions more favorable to fishing and navigation than does un-forested land.

· All natural streams contain varying amounts of dissolved and suspended matter, although streams contain varying amounts of dissolved and suspended matter, although streams issuing from undisturbed watershed are ordinarily of high quality.

· Waters from forested areas are not only low in foreign substances, but they also are relatively high in oxygen and low in unwanted chemicals.

· The belief that forests increase rainfall has not been substantiated by scientific inquiry. Local effects can, however, prove substantial, particularly in semiarid regions where every millimeter of rain counts.

· The air above a forest, as contrasted with grassland, remains relatively cool and humid on hot days, so that showers are more frequent.

· Many areas in India used to get significant rainfall when they were forested are now facing severe draught due to denudation (example Rajasthan desert).

Ocean Acidification

Acid Rain – Acidification

Ø Acid rain refers to any precipitation (rain, fog, mist, snow) that is more acidic than normal (pH of less than 5.6 . pH below 7 is acidic).

Ø Acid rain is caused by atmospheric pollution from acidic gases such as sulphur dioxide and oxides of nitrogen emitted from the burning of fossil fuels.

Ø It is also recognized that acidic smog, fog, mist, move out of the atmosphere and settle on dust particles which in turn accumulate on vegetation as acid depositions.

Ø When rain falls, the acid from these depositions leak and form acid dews.

The pH scales

Ø The pH scale is a measure of how acidic or basic (alkaline) a solution is.

Ø It ranges from 0 to 14. A pH of 7 is neutral.

Ø A pH less than 7 is acidic, and a pH greater than 7 is basic.

Ø It is based on hydrogen ion concentration in an aqueous solution.

Ø pH values decrease as hydrogen ion levels increase.

Ø A solution with pH 4 is ten times more acidic than pH 5, and a hundred times more acidic than pH 6.

Ø Whilst the pH range is usually given as 0 to 14, lower and higher values are theoretically possible.

Gases that cause acid rain Acidic gases:

Ø CO2 (Carbon dioxide): Fossil fuel burning, industrial process, respiration

Ø CH4 (Methane): Paddy fields, wetlands, gas drilling, landfills, decomposition of animals wastes and carcasses.

Ø CO (Carbon monoxide): Biomass burning, Industrial sources: smelting of iron ore, Biogenesis, Plant isoprene's.

Ø SOx (Sulphur oxides): Fossil fuel burning, power plants, smelting of metal sulphide ores, industrial sources, industrial production of sulfuric acid in metallurgical, chemical and fertiliser industries volcanoes, seas and oceans, decomposition of organic matter.

Ø NOx (Nitrogen oxides – NO, NO2 and N2O): Fossil fuel burning, lightning, biomass burning, forest fires, oceans, power plants.

Ø Formic acid (HCOOH): Biomass burning due to forest fires causes emission of formic acid (HCOOH) and formaldehyde (HCHO) into the atmosphere. Large fraction formaldehyde gets photo — oxidation and forms formic acid in the atmosphere.

Ø Carbonic acid (H2CO3): Carbon monoxide and carbon dioxide dissolve in water (water vapor) to form carbonic acid.

Some points on N2O and NO:

Ø Are neutral in nature.

Ø N2O3, NO2 and N2O5 are acidic in nature.

Ø These acidic oxides react with water and produce acids like HNO3 (nitric acid) and HNO2 (nitrous acid) which causes acid rain.

Ø The neutral oxides are comparatively less, and they combine with oxygen and produce nitrogen dioxide.

Ø Thus, N2O and NO are indirectly involved (2NO +O2 —>2NO2) in causing acid rain.

Types of Acid Deposition

Ø ―Acid rain‖ is a broad term referring to a mixture of wet and dry deposition (a form of deposition material) from the atmosphere.

Wet Deposition

Ø If the acid chemicals in the air are blown into areas where the weather is wet, the acids can fall to the ground in the form of rain, snow, fog, or mist.

Ø As this acidic water flows over and through the ground, it affects a variety of plants and animals.

Dry Deposition

Ø In areas where the weather is dry, the acid chemicals may become incorporated into dust or smoke and fall to the ground through dry deposition, sticking to the ground, buildings, vegetation, cars, etc.

Ø Dry deposited gases and particles can be washed from these surfaces by rainstorms, through runoff. This runoff water makes the resulting mixture more acidic.

Ø About half of the acidity in the atmosphere falls back to earth through dry deposition.

Chemistry of Acid Rain:

five basic steps are involved in the formation of acid rain:

1. The atmosphere receives oxides of sulphur and nitrogen from natural and human-made sources.

2. Some of these oxides fall back directly to the ground as dry deposition, either close to the place of origin or some distance away.

3. Sunlight stimulates the formation of photo-oxidants (such as ozone ) in the atmosphere.

4. These photo-oxidants interact with the oxides of sulphur and nitrogen and other gases (like NH3) to produce H2SO4 (sulphuric acid) and HNO3 (nitric acid) by oxidation.

5. Acid rain containing ions of sulfate, nitrate, ammonium and hydrogen falls as wet deposition.

Harmful effects of acid rain

Ø Acid precipitation affects both aquatic and terrestrial organisms.

Ø It also damages buildings and monuments.