Biodiversity and the effect of human interaction

Biodiversity is the variety of all the different species of organisms on Earth, or within an ecosystem. High biodiversity means many species and many different alleles — the foundation for stable, resilient ecosystems.

Why is biodiversity important?

A species-rich community is more interdependent and so more resilient:

• Plants stabilise soil, prevent erosion, regulate climate.
• Predators control pest populations.
• Insects pollinate crops.
• Decomposers recycle nutrients.

Loss of biodiversity → ecosystems are more vulnerable to disease, climate change and other shocks.

Threats to biodiversity from human population growth

The human population has more than doubled since 1960. More people consume more resources and produce more waste. Three big threats are examined at GCSE: pollution, land use and deforestation/peat destruction.

1. Pollution

Pollution can be in:

Water

• Sewage and fertiliser run-off cause eutrophication: nitrate-rich water → algal bloom → algae die → bacteria decompose them, using up O₂ → fish die.
• Toxic chemicals (e.g. pesticides) can build up in food chains (bioaccumulation, e.g. DDT in birds of prey).

Air

• Smoke and acidic gases (SO₂ from burning fossil fuels) form acid rain that damages forests and lakes.
• Particulates harm respiratory health.

Land

• Toxic chemicals from pesticides, herbicides and industrial waste persist in soil.
• Landfill waste leaches chemicals.

2. Land use

As humans claim more land for building, farming, quarrying and dumping waste, less is left for wild species.

• Hedgerows removed to enlarge fields → lose habitat for many farmland birds.
• Peat bogs drained for farming or harvested for compost (see below).
• Wetlands drained for housing.

3. Deforestation

Large-scale clearing of forests, especially tropical rainforests, is happening to:

• Provide land for cattle (beef).
• Grow rice for an expanding population.
• Grow crops to make biofuels (palm oil, soya, sugarcane → ethanol).
• Provide timber.

Effects:

• Loss of biodiversity (rainforests house >50 % of land species).
• Increased CO₂ in atmosphere — trees are no longer photosynthesising; many are burnt.
• Loss of habitats; soil erosion; change in local water cycle.

4. Peat bog destruction

Peat is partially decomposed plant material laid down in anaerobic, acidic wetlands over thousands of years. Peat bogs:

• Hold huge amounts of carbon ("locked away" — preventing global warming).
• Are unique habitats for plants, insects and birds.

When peat is burned or used as compost:

• Habitats are destroyed → biodiversity falls.
• Stored carbon is released as CO₂.

Many countries (UK included) are encouraging peat-free compost.

What helps biodiversity? (Linked to B7.7)

• Breeding programmes for endangered species.
• Protected areas / nature reserves.
• Reintroducing hedgerows and field margins to give wild species space.
• Reducing deforestation through sustainable forestry.

Links

Sets up B7.6 (global warming), B7.7 (maintaining biodiversity), and B7.9 (food security).