Extinct animals from the early holocene extinction

Species affected by humans

Holocene extinction:

The Holocene extinction is the current ongoing extinction event. There have been many extinctions of numerous species, and a large amount of degradation of biodiverse habitats (rainforests, coral reefs), with reduction in biodiversity happening estimating to be happening at 100 - 1000 times more than the normal rates. This continuing extinction event it thought to bet the results of increased human activity beginning at the end of the last ice age. One major extinction event was loss of the megafauna (which are theorized to have been hunted to extinction) due to the increase in humans as a 'global superpredator'. Extinctions have continued to happen on every land mass and in every ocean. The reduction in biodiversity has occurred not only from direct hunting of species, but also through indirect influencing of environments, and pollution of natural ecosystems.

Bramble Cay Melomys:

The Bramble Cay Melomys was a species of rodent found only in the north-eastern edge of the Torres Strait Islands. Last reports of sightings of the mammal were in 2009. It's disappearance from the ecosystem is the thought to be the first reported mammalian extinction as a result of human-induced climate change. The cause of the extinct has been identified at sea-level rise, which flooded the island at multiple occasions, ruining their natural habitat. It is estimated that 97% of their habitat was lost in the last 10 years.

Bramble Cay Melomys

Arunachal Hopea Tree:

The Arunachal Hopea Tree was a species found widely around India prior to its extinction. It was exploited for use a housing material, and hasn't been sited since 1996. This is an example of how humans have directly impacted upon species, utilizing organisms for their own benefit and causing their extinctions.

Arunachal Hopea Tree

Rabbits are an introduced species in Australia

Land clearing in Australia

Land clearing in QLD

Mining requires land clearing however the land will later be rehabilitated

Total extinction in each animal category has accelerated in modern times

The Greenhouse effect

Increasing population:

The population of humans worldwide is growing faster than ever before for several reasons. Improved food production and distribution, medical breakthroughs, increased international travel ability, and improved water availability have improved longevity. Because more people are living longer and healthier lives, there is an increased demand for resources and space on the environment. Solutions are becoming available as technology improves.

Graph of human population over time

Agriculture:

The trend in human population growth can be traced to the very beginnings of agriculture. There have been many agricultural revolutions throughout human history. This has an immediate effect on populations.

Agriculture disrupts the natural soil structures and processes. Soil erosion refers to the removal of topsoil to distant areas by wind and water. The main causes are:

• Removal of vegetation/leaving land fallow

• Soil cultivation practices that break up the soil structure

• Increased stocking rates of hard-hooved animals, leading to the break-up of the soil

• Compaction of the soil by heavy machinery with loss of rain infiltration and increased water pooling on the surface

• Salinization of soils, which changes soil structure

Agriculture can also lead to pollution via harmful substances. This may take the form of:

• Fertilizers

• Pesticides

This leads to eutrophication.

Australian agriculture

Introduced species:

As humans expanded, new species of animals and plants were brought from overseas for many reasons. Introduced species of plants and animals are a major problem in Australia. Since European colonization of Australia, many species of plants and animals have been either deliberately or accidentally introduced into Australian environments. Many of these animals outcompete native species.

Marine life is also susceptible to threats from introduced species. Ballast water is used by ships to improve their stability on long ocean voyages. It is picked up when cargo is loaded and discharged upon arrival at the destination. Any marine species picked up accidentally are transported to new ecosystems. The Northern Pacific Sea star is an aggressive predator that has had major impacts on native species in Victorian and Tasmanian waters.

Land clearing:

To sustain growing populations and create space for agriculture and living space, land must be cleared. Land clearing refers to the removal of native vegetation. This contributes to soil salinization and erosion, land clearing removes the nesting sites and habitats of native animals. Many of these animals are territorial and are not able to re-establish themselves elsewhere.

As demand for water increased for consumption and agriculture, waterways began to be altered. Extraction of water from surface waterways has led to a drop in water levels in rivers as well as the loss of some wetlands. The amount of water extracted by landowners is tightly regulated by the government to make irrigation a more sustainable practice in the long term.

As technology improved and infrastructure increased to cope with higher human populations, more of Earth's mineral resources were needed. Mining represents a rich source of income in Australia where various ores are extracted from the ground.

• The extraction and refining of ores leaves behind chemical pollutants

• Acid wastes are produced, which change the acidity of waterways

• The topography of the land is altered

• Old buildings and machinery may be left behind afterwards

• Air pollution may lead to acid rain

Extinction:

Habitat loss is the leading cause of extinction around the world. Most historic extinctions have occurred on islands because even small losses of habitat have devastating effects there. Island populations are often relatively small, and thus particularly vulnerable to extinction. Of the 90 species of mammals that have gone extinct in the world in the last 500 years, 73% lived on islands. Another 19% lived in Australia. Recently the extinction crisis has moved to continents. Almost 730 organisms have gone extinct since 1600.

Changing climate:

Earth's climate systems are complex and reply on the exchange of energy and matter between the four spheres of the Earth (Hydrosphere (water), lithosphere (land), atmosphere (gases) and biosphere (living things).

Life on Earth is made possible by the presence and nature of our atmosphere and hydrosphere. The atmosphere and oceans act as mechanisms to trap solar radiation throughout the day, storing it at night and preventing catastrophic temperature differences between day and night. Atmospheric gases keep the atmosphere warmer than it would otherwise be. The moon, which has no atmosphere, experiences temperature swings of almost 300 degrees Celsius between day and night. This phenomenon is called the greenhouse effect.

The enhanced greenhouse effect occurs when there is an increase in the concentration of greenhouse gases in the atmosphere. This results in more heat energy being absorbed by the land and oceans. Australia's climate has always undergone periods of cooler or warmer, wetter or drier conditions, but the general trend over the last century is one of warming.

The human factors contributing to climate change are:

• Increased carbon dioxide from the burning of fossil fuels such as coal, petroleum and natural gas

• The impact of modern agricultural practices

• Widespread land clearing

Reconstructing past ecosystems from fossil DNA

How the past informs the future

Biologists can estimate rates of extinction by studying recorded extinction events, examining the fossil record and by analyzing modern trends in habitat loss and disruption. Studying a wide array of recorded extinctions and currently threatened species, conservation biologists have identified human-induced selection pressures that seem to play an important role in many recent extinctions.

• Over exploitation of resources - harvesting resources in a non-sustainable way. The ability of nature to rebound is stretched beyond its limit.

• Introduced species - causes changes in biotic factors.

• Disruption of ecological relationships - established food webs are disrupted due to the loss of available niches, with alterations in the abundance and distribution of populations. This may involve the loss of genetic variability, habitat loss and fragmentation of populations.

  1. Habitat loss can affect biodiversity on three levels:

  2. Genetic diversity refers to intraspecies diversity in traits that makes a population more resilient to environmental changes.

  3. Species diversity is the variety of different species available in an ecosystem. It is sometimes referred to as 'species richness'. Food chains rely on many species interacting for energy and nutrients to be transferred.

  4. Ecosystem diversity is the variety of ecosystems available in a broader area such as continents and globally.

By looking at evidence for changes in climate over time, we can understand more about the factors that may determine the distribution of flora and fauna In present-day organisms. We can use this to predict the movement and distribution of organisms in the future.

South American marsupials have been dominated by placental mammals over time. This could happen in Australia given the same conditions. To find out exactly what those conditions were is the role of the paleontologist. Paleontologists can compare past life to modern groups of organisms to discover genetic relationships and the ages of different groups. The fossil record for kangaroo-like marsupials in Australia extends back 45 million years to a time when rainforests were widespread.

Scientific models are a way to help us understand, define and quantify scientific phenomena. They have been used widely to help scientists predict future events, and currently there are many efforts being dedicated to understanding how climate change and human activity will affect current ecosystems.

The UNEP (United Nations Environmental Programme) are driving efforts to investigate the impacts of human activity on future ecosystems by creating statistical computer models.

• PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems): uses statistics about past ecosystem events to predict future changes. It gathers data that currently exists about biological communities, and models how they will respond to loss of habitat and degradation. This can be used to help inform policy decisions leading into the future.

• https://www.predicts.org.uk/

• GLOBIO (Global Biodiversity model for policy support): assesses human impacts specifically, and uses information contained in literature about the cause and effect relationships within terrestrial environments.

• https://www.globio.info/

• Madingley Model: attempts to model interactions within all the worlds ecosystems. It investigates the processes that drive organism abundance and distribution, and uses these to predict ecosystem change based on postulations by climate scientists. By creating these mathematical models, this system has begun simulating how future socio-economic circumstances might change the structures of ecosystems.

• https://madingley.github.io/

• Center for Biological Diversity: works to secure a future for all species that are hovering on the brink of extinction. They do so 'through science, law and creative media, with a focus on protecting lands, waters, and climates that species need to survive.

• https://www.biologicaldiversity.org/

• IUCN (International Union for Conservation of Nature) Red list of Threatened species: The world's most comprehensive information source on the global extinction risk status of animals, plants and fungus species. The red list acts as an indicator of the health of the world's biodiversity and is used to inform and catalyse action for conservation and policy change that is critical for protecting the natural resources we need to survive. It provides information about range, population size, habitat and ecology, use and/or trade, threats, and conservation actions that help inform conservation action.

• https://www.iucnredlist.org/

Researchers, as part of the genes-to-ecosystem initiative, are attempting to build models and predict impacts of climate change on future communities by analyzing and identifying foundational species. Using experimental field traits, and genome analysis, scientists are aiming to predict how essential species would react to changing global temperatures, and therefore impact wider ecosystems.

Impacts of climate change on the ocean

Impact of climate change on ecosystems

Impacts of climate change

Models to predict impacts on biodiversity

Scientists recognize three main models used to predict population growth in organisms: geometric growth, exponential growth and logistic growth.

• Geometric growth: when the environment is ideal and there are no factors that limit expansion of the population, populations grow at either geometric rate or an exponential rate. Geometric growth is evenly distributed throughout the year. In geometric growth:

  • There is a fixed rate of population increase within a given time

  • Population sizes are compared to the previous year at the same time.

  • The equation to calculate the population N at any time t in the future is:

Exponential growth: when growth is intermittent during the year, but resources are still unrestricted, the growth rate is exponential. The shape of the growth rate curve is always J shaped. For example, bacteria in a Petri dish grow exponentially.

Logistic Growth: this is the most common way in nature that populations grow. There is an initial growth in the population, but this slows down because there is competition for limited resources. The graph is S shaped. The logistic model introduces the concept of carrying capacity (K) for any ecosystem. The carrying capacity is the largest population size of any species that an ecosystem can support without negative effects. This is a changing variable based on things like rainfall or resource availability.

The past is the key to the future, and the more scientists learn about past ecosystems, the better able they will be to manage them in the future.

Paleontology provides excellent data for building models to help guide future ecosystem management. Fossils provide invaluable information about what past ecosystems were like. Through the study of fossils we can create models of the environmental conditions of past organisms and predict changes to present species that are similar or closely related to them. Such predictions are more accurate the more recent the intel is, predictions based on other information are much less reliable as the environmental conditions could be wildly different form modern conditions.

Paleontologists can use the fossil record to:

• Determine how organisms change over time

• Understand how organisms may be related

• Understand why organisms become extinct

• See the effect of species extinction on other species

• Recognize past distribution changes to organisms to inform modern changes.

Fossil evidence may inform of interspecies relationships, biotic and abiotic factors of past ecosystems and provide evidence for climate change over time. This fossil evidence therefore provides us with the factors that may have determined the distribution of flora and fauna in the past and use this to inform modern distribution and even predict future distribution.

Many sites around Australia are rich in fossil samples and provide information about the species and environment in that area.

Mining sites must be filled as part of rehabilitation

Restoration of mining sites

Mining has been used prolifically in Australia as a method of obtaining materials from the Earth. It involves physically creating large excavations to reach deep below the ground, and this practice evidently has large impacts on ecosystems around mining sites. It compacts and reduces the fertility of soil, leeches toxic chemicals into the ground, and eradicates biotic lifeforms. Restoration of decommissioned mining sites is essential to ensuring the continuing survival of ecosystems within our unique Australian environment. When a mining operation is being proposed in Australia, the mining company is required by law to follow strict guidelines including submitting information on how they intend to ensure minimal harm to the environment.

The Mining Act 1992 establishes definitions of harm and the required management of mine sites to minimize harm. It is unrealistic to expect absolutely no long-term damage from mining, but careful planning can help keep the effects to a minimum. Mining companies operate on the principles of sustainable development which state:

• The next generation should not be left with a less healthy and diverse environment

• Biodiversity and environmental integrity must be conserved

• Decisions should err on the side of caution. The burden of proof needs to be on the company to convince that their plan is ecologically sustainable.

• Limits should apply according to the ability of the environment to supply required resources

• Human efficiency and ecological resilience are important factors

Previous to mining, some projects involved biodiversity offset initiatives. This involves moving wildlife to new areas in order to preserve biodiversity. Mine reclamation is the process of restoring mining sites, attempting to return them to their natural state. It begins by filling in the mine using material suited to the region, to ensure that no earth will collapse unexpectedly after abandonment. Aims are to reconstruct a functional ecosystem, by best replicating previous soil, chemical, and biological conditions. The area is then landscaped to better resemble a natural state. Seeds of native plants are then sown to assimilate the site back to the previous environmental conditions.

Bioremediation is a newer technology used to restore mining sites, particularly where bad chemicals have leeched into the soil. The technique uses naturally occurring microorganisms to break down the harmful substances. This can either be done in situ (on site) or ex situ (off site). Some microorganisms are naturally able to metabolize toxic substances, and turn them into less harmful substances. Bioaugmentation is the process of enhancing microbes which naturally grow at the site, and increasing their numbers so that they are able to metabolize the harmful substances at a faster rate. Some techniques take a sample from the site, and then use this to grow up the desired microbes. They are then injected back into the site, and left to remediate the soil.

Strategies for environmental control and rehabilitation include:

• Removal of any infrastructure

• Making sure that mine entrances and shafts are sealed and secure

• Removal of contaminated soil

• Revegetation and landscaping of the environment

• Regular testing of local waterways for signs of chemical contamination from run-off

• Control of gas emissions

• Control of dust

• Scheduling of truck movements to limit noise pollution

• Stabilizing all underground tunnels

• Treatment of tailings and other chemical waste

• Fencing of the site to protect it during reestablishment

• Control of weeds and feral pests

Bioremediation process

Restoration of farm land into its natural state

Restoration of agricultural land

Agriculture has been widely used by humans to mass-produce products. The practice includes the production of livestock , as well as plant food sources, it is possible to sustainably farm and, however such practices have not often been followed, leading to wasteful consumption of water, pollution, leeching of all nutrients from soils, increased desertification, and degradation of land. Agroecological restoration is practice used to restore natural systems within agricultural lands, in order to improve biodiversity, and in turn maximize sustainability. The suitability of lands to support ecosystems can be restored, but requires a number of things:

• Restoration of nutrients to the soil (improves fertility)

• Re-enabling vegetation (by replanting appropriate organisms)

• Water conservation

One major issue with over-used farm land is that the soil becomes degrade, and erodes. This process is called desertification, and has occurred all over the world. To remediate this, efforts towards site stabilization are taken, including planting of organisms with stable root systems to anchor the site, and avoiding monoculture practices.

Problems and their solutions:

Soil erosion

• • Use minimum till/direct drilling techniques

  • Do not leave soil fallow for long periods

  • Reduce stocking rates for livestock and employ rotational grazing

  • Retain stubble after harvest

  • Grow crops on slopes

  • Use channels and terraces to store and redirect water

  • Leave riparian buffer strips to reduce riverbank erosion

  • Make windbreaks

  • Use drip irrigation instead of floor irrigation

Salinization

• • Replant deep-rooted perennial plants

  • Use drip irrigation instead of floor irrigation

  • Mulch garden beds

  • Plant salt-tolerant plant species

  • Time sprinkler systems

Eutrophication

• • Reduce run-off into streams of nitrogen and phosphorus-containing fertilizers and detergents

Introduced species

• • Use quarantine and border control methods

  • Use methods of control such as biological and chemical

  • Manage weeds by physical removal in appropriate situation

Land clearing

• • Replant deep rooted native vegetation

  • Re-establish ground cover

Pesticide residues

• • Use integrated pest management systems that incorporate several strategies besides chemicals (for example, traps, barriers and genetic engineering).

Process of good and bad land management strategies

Replanting native species

Common land management practices

Case studies of land management and biological controls

There is a certain point at which a living thing becomes a pest and this depends on its ability to reproduce quickly as well as its effect on the ecosystem. Some introduced species that were brought in for sport, recreation or other purposes could exploit their conditions in their new environment and establish themselves quickly in the environment.

The Galaxias fish is a native freshwater fish who was affected by the introduction of the mosquitofish. For land animals such as bandicoots, wallabies, quolls and marsupial mice, the threat is from feral cats, dogs and foxes. Their successful reintroduction requires safe release areas such as those with pest-proof fencing, which is an expense that affects the success of any captive breeding programs.

Australian crops have succumbed to an assortment of fungi, bacteria, insects and herbivores that are introduced species. Paterson's curse is a hardy European plant with a taproot that enables it to survive drought conditions. Throughout late spring, these plants reproduce rapidly and take over pastures very quickly. The term 'Salvation Jane' was given as another name for its ability to sustain cattle and horses throughout droughts, however it plant also leads to liver toxicity after long term ingestion.

Pesticides can be a quick and effective chemical control for getting rid of pests. However, they can cause problems due to bioaccumulation (where they build up in organisms) and biomagnification (where predators receive larger doses of the toxin). Scientists now favor the use of biological control agents. The best strategy involves integrated pest management, where a combination of strategies is used to control the organism. This involves the use of biological measures to control pests and limits the use of chemicals to narrow-spectrum agents that target species. Biological control is not always successful, such as with the cane toad.

Larger insects are often used to control smaller pests

There are four kinds of biological control agents:

1. General predators: organisms that consume a great variety of pest species (e.g. Ladybugs eat aphids, caterpillars and small beetles). Recent research has shown that green ants are a cost-effective method of controlling most pests that attack mangoes. Almost all ecological disasters resulting from biological control have been due to the introduction of general predators.

2. Specialized predators: organisms that target one pest species or group of species. Introduced weeds often choke waterways. The plants grow freely, without any environmental control, and affect the local organism populations. Too many weeds limits the populations of other species that native animals require for food and shelter. A small South American Weevil, the natural predator of the water weed Salvinia was released in 1980 with great success.

3. Parasites: organisms that live off another organism to its detriment. Wasps and flies sometimes lay their eggs on the bodies of hosts. When the eggs hatch, the larvae feed on the body of the host (e.g. mango worms) which can cause the host's death. Wasps are being used to control the native stem-girdler moths that can decimate macadamia and pecan crops in Queensland. The wasps lay their eggs in moth eggs, which are then consumed by the wasp larvae.

4. Microbial diseases: diseases caused by bacteria, fungi, and virus that target species and cause death through illness. Examples include the myxomatosis virus and calicivirus, which were introduced to control rabbit populations.