What is biodiversity and why does it matter?
Biodiversity is the variety of all the different species (kinds) of living things on Earth, or in one ecosystem.
Why high biodiversity is good:
- It makes an ecosystem stable. Species depend on each other for food and shelter. If one food runs out, animals can eat another.
- Living things keep the physical environment steady, for example plants hold soil and keep air and water clean.
- People get food, medicines, materials and new genes for crops from many species.
The future of the human species depends on keeping a good level of biodiversity. Many human activities are reducing it, and only recently have we started to act to stop this.
Waste management and pollution
The world's human population is growing fast and people use more resources each year. So more waste is produced. If it is not handled well, more pollution happens:
- Water: sewage, fertiliser and toxic chemicals wash into rivers, lakes and seas.
- Land: landfill, toxic chemicals such as pesticides and herbicides, and plastic rubbish.
- Air: smoke and acidic gases from burning fuels (sulfur dioxide, nitrogen oxides) cause acid rain.
Pollution kills plants and animals, and this lowers biodiversity.
Land use and peat bogs
Humans take land away from other species to build homes, roads and shops, to quarry rock, to farm and to dump waste (landfill).
Peat bogs
Peat is a thick, wet layer of dead plants that never fully rotted. Peat bogs store a lot of carbon. When peat is drained and dug up to make farmland or garden compost:
- a special habitat and its species are lost, and
- the peat is decayed by microorganisms or burned, releasing carbon dioxide into the air.
Using peat-free compost helps protect bogs.
Deforestation
Deforestation means cutting down large areas of forest. In tropical areas forests are cleared to make room for cattle, rice fields and crops grown for biofuels or palm oil.
Effects:
- Habitats are destroyed, so biodiversity falls.
- Fewer trees take in carbon dioxide for photosynthesis.
- Burning trees and the decay of leftover wood by microorganisms release carbon dioxide.
So deforestation both lowers biodiversity and adds to global warming.
Global warming
Levels of carbon dioxide and methane in the atmosphere are rising, mainly from burning fuels, deforestation, peat loss, cattle and rice fields. These gases trap heat, so Earth's average temperature rises: global warming.
Biological effects:
- Loss of habitat, for example low land flooded as ice melts and sea level rises.
- Species move to new areas as the climate changes (often towards the poles or uphill).
- Changes in when animals migrate and plants flower.
- Species that cannot move or adapt may become extinct, so biodiversity falls.
Maintaining biodiversity
Scientists, governments, farmers and ordinary people can all help:
- Breeding programmes for endangered species, often in zoos, then releasing them into the wild.
- Protecting and regenerating rare habitats, such as mangroves, coral reefs and heathland.
- Reintroducing field margins and hedgerows on farms where only one crop is grown, giving wild plants and animals a home.
- Reducing deforestation and carbon dioxide emissions.
- Recycling resources rather than dumping waste in landfill.
There are conflicts: protecting land can cost money, farmers need income, and people need food and homes. Good decisions balance these needs.
Try it: in the last 3D step, switch on one action at a time and count how many species return. At home, list which of these actions your family or school already does.
Key formulas and definitions
- Biodiversity = variety of all the different species in an ecosystem or on Earth
- High biodiversity → stable ecosystem (less dependence on one species)
- Threats: pollution (water, land, air), land use, peat removal, deforestation, global warming
- Deforestation and peat loss → less CO₂ taken in + more CO₂ released
- Greenhouse gases: carbon dioxide and methane
- Protection: breeding programmes, habitat restoration, hedgerows/field margins, less deforestation and CO₂, recycling
Worked examples
1. A pond has 3 species of insect and a nearby wetland has 15. Which ecosystem is likely to be more stable, and why?
The wetland. With more species, a predator can switch to another food if one prey species declines, so the food web does not collapse.
2. Explain how clearing a forest to grow cattle feed increases carbon dioxide in the air.
Fewer trees remain to take in CO₂ for photosynthesis, and burning the trees and the decay of leftover wood by microorganisms both release CO₂.
3. A gardener buys peat compost. Give two ways this harms the environment.
Peat bogs are a habitat that is destroyed when peat is dug, lowering biodiversity. The peat decays or is burned, releasing stored carbon as CO₂, which adds to global warming.
4. A farmer removes hedgerows to make bigger fields of one crop. Suggest one effect on biodiversity and one way to reverse it.
Birds, insects and small mammals lose their homes and food, so biodiversity falls. Replanting hedgerows and leaving wild field margins gives them habitats again.
Common mistakes
- Saying biodiversity means "the number of animals". It is the variety of different species, plants and microorganisms included, not the number of individuals.
- Thinking deforestation only harms by removing trees. Burning and decay also release carbon dioxide.
- Mixing up global warming with the ozone hole. Global warming is caused by greenhouse gases like CO₂ and methane trapping heat.
- Listing only problems in an exam. Questions often ask for ways to maintain biodiversity, so learn the five actions.