Biodiversity and habitat destruction

Human influences on ecosystems · Habitat destruction · note 1 of 2

Spec 20.2.1, 20.2.2, 20.2.3Download all Habitat destruction notes (PDF)Download all notes (PDF)3 pages

Biodiversity and habitat destructionSpec 20.2.1, 20.2.2, 20.2.3

In short

Biodiversity is the number of different species that live in an area. Habitat destruction reduces biodiversity and is caused by clearing land for housing, crop plants and livestock, by extracting natural resources such as through mining, and by freshwater and marine pollution. Humans also harm habitats by altering food webs, because removing one species affects others.

Biodiversity: The number of different species that live in an area.

A habitat is destroyed when it is changed so much that the organisms living there can no longer survive. This reduces biodiversity.

Reasons for habitat destruction

Increased area for housing, crop plant production and livestock production: forests, grassland and wetlands are cleared to build homes and to grow food for a growing population.
Extraction of natural resources: mining, quarrying and drilling remove soil and rock and destroy the habitat above.
Freshwater and marine pollution: pollutants such as sewage, fertiliser and plastics make water unsuitable for the organisms that live in it.

Damage to food webs

Humans can also have a negative impact on habitats by altering food webs and food chains. Removing one species affects others. For example, if a predator is hunted out, its prey may increase in number and eat too much of the producers. If a producer is cleared, the animals that feed on it lose their food and may die or move away.

Exam tip:

Biodiversity is about the number of different species, not the number of individual organisms.

Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026

Frequently asked questions

How does deforestation affect the carbon cycle?

Deforestation increases carbon dioxide in the atmosphere. Fewer trees are left to take in carbon dioxide for photosynthesis, so less is removed from the air. When the felled trees are burned or decay, the carbon in them is released as carbon dioxide, by combustion or by the respiration of decomposers.

Why is biodiversity important to ecosystems?

Biodiversity, the number of different species in an area, matters because species are linked in food webs, so removing one species affects others. For example, if a predator is hunted out, its prey may increase and eat too much of the producers. Habitat destruction reduces biodiversity and can lead to extinction.

How does deforestation cause flooding?

Deforestation causes flooding because tree roots absorb water and leaves intercept rain. Without the trees, more rain water runs straight into rivers, so they flood more easily. Without tree roots to hold the soil together, rain also washes the soil away, which is called soil erosion.

All 4 questions on Habitat destruction