9.2 Ecosystems Under Threat

2026 Syllabus Objectives

By the end of these notes, you should be able to:

  1. Describe and explain the causes of habitat loss — including the drainage of wetlands, intensive agricultural practices, and deforestation.
  2. Describe and explain the impacts of habitat loss — including loss of biodiversity, genetic depletion, and extinction.

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What Is a Habitat?

A habitat is the natural home of a living organism — the place where it finds food, shelter, and conditions it needs to survive. Examples include rainforests, wetlands, grasslands, and coral reefs.

When a habitat is damaged or completely destroyed, it is called habitat loss. The plants and animals that lived there either die, move away, or struggle to survive. This is one of the biggest threats to life on Earth today.

Causes of Habitat Loss

There are three main causes you need to know:

1. Drainage of Wetlands

Wetlands are areas where the land is covered or soaked with water for much of the year — think of marshes, swamps, bogs, and floodplains. They are incredibly rich habitats, home to many species of birds, fish, insects, and plants.

Why are wetlands drained?

  • Humans drain wetlands to create flat, dry land that can be used for farming or building (housing, roads, factories).
  • Draining is done by digging channels or ditches that carry water away from the land.
  • Once drained, the wetland no longer exists — all the organisms that depended on it lose their home.

Why is this a problem?

  • Many species that live only in wetlands have nowhere else to go.
  • Wetlands also act as natural water filters and flood barriers — draining them removes these important functions.

2. Intensive Agricultural Practices

Agriculture means farming — growing crops and raising animals for food. Intensive agriculture means farming on a very large scale, using every possible method to produce as much food as possible from the land.

How does intensive agriculture cause habitat loss?

  • Land clearance: Large areas of natural habitat (forests, grasslands, wetlands) are cleared to make room for fields and farmland. Wild plants and animals lose their homes.
  • Use of pesticides: Chemicals are sprayed on crops to kill insects and other pests. However, these chemicals also kill non-pest species — including bees, butterflies, and other wildlife — reducing the variety of life in the area.
  • Use of fertilisers: Chemicals added to soil to make crops grow faster can wash into rivers and lakes. This causes eutrophication (too many nutrients in the water), which leads to algae growing out of control and killing other aquatic life.
  • Monoculture: Growing only one type of crop across huge fields (called a monoculture) replaces the natural variety of plants with just one species. This removes food and shelter for many animals.
  • Hedgerow removal: Farmers often remove hedgerows (rows of bushes and shrubs between fields) to make bigger fields for machines. Hedgerows are home to many birds, insects, and small mammals.

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