Biodiversity and human impact · GCSE Biology

Biodiversity

Biodiversity is the variety of all the different species of organisms on Earth, or within an ecosystem.
High biodiversity keeps ecosystems stable, by reducing the dependence of one species on another for food, shelter and maintaining the physical environment.
The future of the human species depends on maintaining good biodiversity, but many human activities reduce it.

The rapid growth of the human population and rising standards of living mean more resources are used and more waste is produced.
Water can be polluted by sewage, fertilisers and toxic chemicals. Air can be polluted by smoke and acidic gases.
Land can be polluted by landfill and toxic chemicals; pesticides and herbicides may be washed from land into water.
Pollution kills plants and animals, reducing biodiversity.

Humans reduce the land available for other organisms by building, quarrying, farming and dumping waste.
Destroying peat bogs to make garden compost reduces the area of this habitat and its biodiversity. As peat decays or burns, carbon dioxide is released.
Large-scale deforestation in tropical areas provides land for cattle and rice fields and for crops to make biofuels. It reduces biodiversity and releases carbon dioxide.

Rising levels of carbon dioxide and methane in the atmosphere are contributing to global warming.
Biological consequences include loss of habitat as low-lying areas flood when sea levels rise, changes in the distribution of species as temperature and rainfall change, and changes to migration patterns.

Breeding programmes for endangered species.
Protecting and regenerating rare habitats.
Reintroducing field margins and hedgerows where farmers grow only one crop.
Reducing deforestation and carbon dioxide emissions, and recycling resources rather than dumping waste in landfill.
(Separate sciences) Food security means having enough food; sustainable fishing (net sizes and quotas) and biotechnology, such as mycoprotein from the fungus Fusarium, help.

Eutrophication: fertiliser or sewage washes into lakes and rivers, so algae grow quickly and cover the surface. Plants below get too little light and die, decomposers feeding on them use up the oxygen, and fish and other animals die.
Non-indigenous (introduced) species, such as grey squirrels in the UK, can outcompete native species for food and space, and bring new diseases.
Indicator species show how polluted a place is. Lichens only grow where the air is clean. Bloodworms and sludgeworms survive in polluted water; stonefly nymphs and freshwater shrimps need clean water.
Reforestation and conservation schemes help to restore habitats and biodiversity.
(Separate sciences) Fish farming and factory farming raise food production by limiting animals' movement and keeping them warm, so less energy is lost, but they raise concerns about animal welfare and the spread of disease.

Biodiversity: The variety of all the different species of organisms on Earth or within an ecosystem.
Pollution: Harmful substances added to the environment.
Deforestation: Cutting down large areas of forest.
Peat bog: A wetland habitat made of partly decayed plant material, which stores carbon.
Global warming: The rise in the average temperature of the Earth, linked to greenhouse gases.
Landfill: Disposing of waste by burying it in the ground.
Hedgerow: A line of shrubs and trees that provides a habitat on farmland.
Breeding programme: Breeding endangered species in captivity to increase their numbers.
Food security: Having enough food to feed a population.
Eutrophication: When extra nutrients in water make algae grow quickly, so plants die, oxygen is used up and animals die.
Indicator species: A species whose presence or absence shows how polluted a place is.