Human Ecology Notes

** Natural systems have been upset because humans have not realized that they

not only influence other individuals, other species, and the nonliving world,

but are, in turn, influenced by them.

Some Natural Ecosystem Processes which affect humans

1. maintenance of atmospheric quality

2. generation of soils

3. control of the water cycle

4. removal of wastes

5. energy flow

6. recycling of nutrients

** Humans have changed many of these ecosystem processes -- frequently in a detrimental way.

(Human Population Growth)

-- The total population of humans has risen at a rapid rate, partly because of the removal of natural checks on the population, such as disease.

-- The earth has finite resources, increasing human population and consumption places severe stress on natural processes that renew some resources and deplete those resources which can not be renewed.

A lesson on overpopulation

ie. Kaibab national forest - Arizona - deer

1906 - stable population of 4,000 deer

- bounty was placed on their predators

(1906-23) deer population swells and overgrazing begins -- over 6,000 predators killed

(1924-25) of the 100,000 deer present -- over 75% die - chiefly of starvation & malnutrition

1939 - fewer than 10,000 deer remained

** Destruction of natural enemies is not always good for a species -- it can lead

to its extinction or near extinction. (Will this also happen to Homo sapiens?)

(Some specific human influences on Ecosystem Factors)

1. Increasing numbers:

-- results from an increased human life span

-- health advances largely led to this

2. Food: shortages and inadequate nutrition lead to starvation and malnutrition

-- population growth is outpacing food production in many world regions

starvation: body lacks sufficient calories for maintenance

malnutrition: diet lacks specific substances needed by the body

3. Soil: much loss of fertile topsoil due to erosion and poor management

-- the use of biocides has contaminated the soil (no prior assessment was taken of their environmental impact)

-- some causes of topsoil loss include; cutting forests, farming dry grasslands, damming rivers, draining wetlands, etc.

-- much valuable farmland has been lost due to increasing urbanization & suburbanization

4. Water: much waste occurs -- cutting forests has led to increased, uncontrolled runoff

-- water pollution leaves water unfit for use and the living things remaining in it unfit for consumption (typical water pollutants include phosphates, heavy metals, and PCB's)

biomagnification: increase in the concentration of a substance (poison) in living tissue

as you move up the food chain

(ex. tuna and swordfish, water birds and birds of prey from DDT -- thin shelled eggs)

-- This has particularly hurt the peregrine falcon & bald eagle.

5. Wildlife: much destruction and damage has been done to many species (hunting, fishing, etc.)

exs. passenger pigeon, dodo, great auk, bison, carolina parakeet

** Other problems include habitat destruction, importation of some organisms have caused problems for native organisms. (ex. rabbit - sheep {Australia}, starling & english sparrow, mongoose -birds & mammals {West Indies} We also have alien invasive species which have caused problems for our area in Northern New York. These include the Water Chestnut, Eurasian Water milfoil, Alewife, Zebra Mussel, and Purple Loosestrife. A great source of information in reference to these invaders can be found at the following link.

Vermont DEC Aquatic Nuisance Species Page

6. Fossil Fuels: are becoming rapidly depleted/add to air pollution problems

The search and demand for additional energy resources also impact ecosystems in a negative way. Industrialization has brought an increased demand for and use of energy.

7. Nuclear fuels --- environmental dangers exist in reference to obtaining, using, and storing the wastes from these fuels

8. Air: is becoming increasingly polluted

a.) Greenhouse effect

adding carbon dioxide to the earth's atmosphere may be increasing its temperature

(holds in the earth's heat radiation

b.) Acid Rain

-- sulfur dioxide (also nitrogen oxides) from coal burning sources + rain = ACID RAIN

(Acid rain kills aquatic life, crumbles buildings, and has many other effects, etc.)

c.) Ozone Depletion

-- CFC pollution from refrigerants and plastics are destroying our stratospheric ozone layer ... this layer shields us from incoming ultraviolet radiation .... increased skin cancers and cataracts are resulting from this destruction

9. Living space/available land: is greatly decreasing as a result of increasing population

-- creates increasing stress on individual humans

-- we are also taking up living space and resources needed by other organisms

10. Forests: are becoming increasingly depleted as a result of timber needs

& the need for more agricultural land

-- the direct harvesting of timber has destroyed many forests

-- this destruction also impacts land use and atmospheric quality

11. Affluent human lifestyles have led to waste disposal problems. (solid, chemical, nuclear)

12. Insects: our chief competitors for food

-- we have destroyed many beneficial

insects and many enemies of harmful insects with insecticides

13. Land use (includes increasing urbanization and the cultivation of marginal lands)

-- this decreases the space and resources available to other species

14. Pollution -- this changes the chemical composition of the soil, air, and water

Some Other Factors which influence environmental quality

1. Population growth and distribution

2. Capacity of technology to solve problems

3. Economic, political, ethical, and cultural views

Some examples:

a.) Wealthy people in the developed world tend to have fewer children.

b.) Some countries like China have laws concerning the number of children a couple may have without penalty.

c.) In some countries such as many in Latin America where the Catholic Church is a dominant institution, families tend to be larger as birth control violates church law.

d.) In some poor cultures in third world countries, having many children is seen as a means of having economic security in old age.

What are some ways we are attempting to deal with environmental degradation?

a.) (Species Preservation)

-- Some efforts to sustain endangered species have included habitat protection

(wildlife refuges and national parks) and wildlife management (game laws and fisheries).

-- Animals which were once endangered but are presently successfully reproducing and increasing their numbers are the bisons, gray wolves and egrets.

-- Endangered animals which are currently responding to conservation efforts and

beginning to make a comeback are the whooping crane, bald eagle, and peregrine falcon.

** The future of many species remains in doubt.

Human activities that degrade ecosystems result in a loss of diversity in the living and nonliving environment. These activities are threatening current global stability.

b.) [Ways to Reduce Air Pollution]

1. Use fuels which contain less pollutant, such as low sulfur coal and oil.

2. Utilize industrial or energy producing processes which minimize the creation of pollutants.

3. Remove pollutants by using such devices as afterburners or catalytic converters before they enter the air.

4. Design new products which meet basic needs without generating pollution.

** There are laws which regulate and guide the use of natural habitats.

c.) SEQR: A New York State law designed to provide the

opportunity for citizen review and comment of

the environmental impact of any proposed development that has been

determined to have significant impact on the environment.

d.) [Some Methods of Controlling Harmful Insects]

1. Chemical controls (insecticides) (many drawbacks)

2. Biological controls

[What are some methods used in the Biological Control of Insects?]

1. Introduction of natural enemies. (ex. praying mantis)

2. Use artificial sex hormones to lure insects to their death. (pheromones) (ex. gyplure -- male gypsy moths)

3. Sterilization and release of male insects. (ex. irradiation of the screwworm fly with cobalt-60)

-- Note: The screwworm fly only gets to mate once, so she is out of luck if she mates with a sterile male!!

4. Inspection of all materials before entering the country to prevent pest introduction.

5. Destroy breeding places of insects. (may have negative environmental consequences on other species however)

6. Rotate crops so that harmful insect species can not build up in numbers and

concentrate on destroying one crop.

7. Plan the time in planting certain crops. (ex. plant cotton early so that its flowers

mature before the boll weevil lays eggs in the cotton)

How can individual and societal choices contribute to improving the environment?

1. Through a greater awareness and application of ecological principles, each individual can help to assure that there will be suitable environments for succeeding generations on our planet.

2. Individuals in society must decide on proposals which involve the introduction of new technologies. These decisions must assess environmental risks, costs, benefits, and trade-offs. Some basic questions for assessing the value of these technologies might include:

a.) What could this technology do to the environment?

b.) What are the odds this technology would have this effect?

c.) How do scientists and engineers know what this technology will do to the environment?