3.6 - Human Impact on the Environment

Extinction

Total loss of a species

Explain why endangered species are at risk of becoming extinct

Few breeding pairs left

Reasons for extinction

• Natural selection

• Habitat destruction such as deforestation and loss of hedgerows

• Pollution such as PCBs and oil

• Hunting and collecting

• Competition from domestic animals

Conservation

Sensible, planned management of the biosphere and ecosystems, enhancement of biodiversity locally and protecting gene pools

Examples of conservation methods

• Habitat protection by nature reserves and SSSIs (sites of special scientific interest) protected by law

• International cooperation restricting trade - trade in endangered species and products derived from them, like skins and ivory, are restricted or banned. This is an international agreement

• Captive breeding programmes by zoos and botanic gardens enhance species numbers

• Sperm banks and seed stores preserve gene pools for the future

• Reintroduction programmes enhance the numbers of endangered species

Conservation of species ensures…

Conservation of existing gene pools

Importance of conserving gene pools

• Ethical reasons;

  • unethical to drive species to extinction and reduce biodiversity as the long term impacts are not yet fully realised

• Loss of potentially useful genes to man and the species

  • Plants may provide new medicines for the future

  • Many crop plants have wild relatives that may have useful genes that could be bred back into crops to increase productivity

• Reduced gene pools make species more vulnerable to extinction as there is less variation

Agricultural exploitation

The need to increase efficiency and intensity of food production to meet increasing demands by a rapidly increasing human population

Conflicts in agricultural exploitation

Between the need for conservation of species and the demand for increased food production

Deforestation

Removal of trees to use as timber/fuel/to repurpose the land use for agriculture or building

Consequences of deforestation

• Soil erosion – soil is no longer protected from rain by the canopy; as roots decompose, they no longer hold the soil together so it is eroded by wind and rain.

• Flooding - evaporation from soil removes less water than transpiration, waterlogging encourages denitrification and soil loses nitrates.

• Habitat loss reduces biodiversity.

• Less photosynthesis means that less CO2 is removed from the atmosphere. CO2 is a ‘greenhouse gas’, increased CO2 leads to global warming and climate change.

Solutions to deforestation

• Managed forests —> sustainable replanting and regeneration; Replanting the correct mix of species, the correct distance apart, and allowing them to regenerate.

• Protecting areas.

• Preserve natural woodland to enhance biodiversity

• Selective felling.

Overfishing

Where fish are caught at a higher rate than they reproduce and grow. Occurs to the point where increased fishing efforts lead to declining catches

Consequences of overfishing

• Fish populations may be reduced in size to the extent that they lose genetic diversity.

• Size of fish caught is reduced as they don’t have time to grow.

• Fish population has fewer individuals and cannot replace harvested fish.

Solutions to overfishing

• Quotas are a maximum mass of fish that can be harvested; heavy fines are imposed for exceeding government set quotas.

• Restricted fishing seasons, particularly to allow fish to reproduce.

• Exclusion zones preventing fishing in certain areas.

• Increased mesh sizes allows smaller fish to escape and grow to breeding size.

• Limiting the size of fishing fleets so that not as many fish can be caught

Fish farming

Where fish are intensively reared in ponds/tanks or nets; sea-fish are usually reared in large netted areas of the sea. This is one solution to overfishing.

Consequences of fish farming

• Less fish need to be harvested from the wild, allowing fish stocks to replenish.

• Fish have been selected for high growth rates and therefore large size and increased yield.

• Excess fish food, egesta and excreta fall out of the nets and can cause eutrophication in the marine habitats.

• Parasites and diseases spread quickly through the overcrowded fish.

• Prophylactic antibiotic use may lead to antibiotic resistance and using pesticides to control parasites will harm marine invertebrates.

• If farmed fish escape they could outcompete wild fish or interbreed with them, passing on the alleles for fast growth, pushing wild fish to extinction – some farmed fish have been engineered to be triploid to avoid this issue.

• The feed is often made from harvested wild fish.

Planetary boundaries

Define the ‘safe operating space’ for all of humanity, including all governments, organisations and communities, as a precondition for sustainable development. If the impact of human activities exceeds these thresholds, there is a risk of abrupt and irreversible environmental change.

The 9 planetary boundaries

• Biodiversity

• Climate change

• Nitrogen

• Land use

• Fresh water

• Chemical pollution

• Aerosol

• Ocean acidification

• Ozone

Biodiversity boundary

This describes biodiversity loss and extinctions. The cause is an increased demand for food, water and natural resources. Changes in habitats such as coral reef bleaching caused by ocean acidification decreases biodiversity as the habitat is unable to sustain the indigenous species. It is important that biodiversity monitoring occurs and that gene banks are used to conserve the genomes of endangered species. Extinction in relation to natural selection; the change of habitats such as marine, tundra; coral reefs and coastal plains and its effect on indigenous species; Biodiversity monitoring; the use of gene banks; public awareness

Status of biodiversity boundary

CrossedC

Climate change boundary

The level of greenhouse gases (e.g. carbon dioxide) have risen dramatically and continue to do so. Scientists believe that the loss of polar sea ice could be irreversible. This could push global temperatures and sea levels up. Destruction of rainforest and weakened carbon sinks in tundra and ocean could accelerate the Earth’s warming and climate change. Greenhouse gases and their sources; the production and use of biofuels; the effect on human populations; the effect on plant and animal populations.

Status of climate change boundary

CrossedNitrogen

Nitrogen boundary

Fertiliser production and application are a concern; nitrogen is fixed into fertilisers but uptake by plants is limited leading to eutrophication.

Status of nitrogen boundary

Crossed

Land use boundary

This describes land converted for human use, e.g. for agriculture. the conflict over land use and food production; changes to farming practice; political considerations.Status of land use bounda

Status of land use boundary

Crossed

Fresh water boundary

Globally, fresh water is becoming scarce because of modification of water bodies and land use change. Desalination of sea water may ease the situation. the need for fresh water; sources of fresh water; desalination.

Status of fresh water boundary

Avoidable

Chemical pollution boundary

This includes air pollution with chemicals such as sulfur dioxide and nitrogen oxides as well as the emission of toxic and long-lived substances such as heavy metals, radioactive materials and synthetic organic pollutants. These can cause reduced fertility and genetic damage, e.g. DDT dramatically reduced bird populations. air pollution including the effects of SO2 and N oxides

Status of chemical pollution boundary

Unquanitified

Aerosol boundary

Air pollution by particulates. Their effect on the atmosphere is complex and has yet to be quantified.

Status of aerosol boundary

Unquantified

Ocean acidification boundary

This is owing to increased carbon dioxide dissolving into oceans forming carbonic acid. Organisms with calcium carbonate shells, such as corals and molluscs, can’t make shells in acid water. This disrupts food chains and webs and could drastically reduce fish stocks. The effect of fossil fuel burning on oceans; Fish farming.

Status of ocean acidification boundary

Avoidable

Ozone boundary

The ozone protects the earth from UV radiation from the sun. CFCs from refrigerants and aerosols caused a hole in the stratospheric ozone layer. Actions taken as a result of the Montreal Protocol mean that crossing of this boundary has been avoided. CFCs and the chemistry of ozone destruction; the effect of the Montreal protocols

Status of the ozone boundary

Avoided