Human causes of habitat destruction

A habitat is the place where an organism lives. Human activities can destroy a habitat by removing it, or degrade it by making it less suitable for the organisms that live there.

Land use and habitat loss

When land is cleared for housing, the existing habitat is replaced by buildings and other developed areas. Organisms may lose places where they find food and shelter.

Land is also cleared to grow crops or raise livestock. The resulting fields or grazing land replace the original habitat and may not provide the conditions or resources needed by the organisms that lived there before.

Resource extraction and pollution

Extracting natural resources can damage habitats. For example, mining can remove vegetation and soil, altering the land where organisms live.

Pollution can degrade freshwater habitats, such as rivers and lakes, and marine habitats, such as seas and oceans. Harmful substances entering the water can make it unsuitable for the organisms living there, even when the habitat has not been physically removed.

Human alteration of food chains and food webs

A food chain shows feeding relationships: each organism is eaten by the next. For example, in the chain grass → rabbit → fox, the arrows point from the food to the organism that eats it. A food web connects several food chains in a habitat because an organism may eat, or be eaten by, more than one kind of organism.

Changes spreading through a food web

Human activity can change the number of organisms in a population, affecting the populations connected to it. For example, if people clear land and remove much of the grass, rabbits may have less food and their population may fall. Foxes that depend on rabbits may then have less food, so their population may also fall.

A change can spread in the other direction too. If human activity reduces the number of foxes, more rabbits may survive. A larger rabbit population may then eat more grass, reducing the amount available.

These changes are not always predictable from a single food chain: foxes may eat other animals, and rabbits may have other food sources. Because the chains are connected in a food web, a change to one population can affect several others. The resulting changes can harm organisms and disrupt the habitat’s living community: all the populations living there.

Effects of deforestation

Deforestation is the removal of trees from an area of forest. It removes the habitat that forest species depend on and changes how the land interacts with water and the atmosphere.

Loss of habitat and biodiversity

A forest provides places where organisms can live. When trees are removed, species that depend on the forest lose their habitat and may no longer be able to survive there. This can reduce biodiversity, the number of different species living in an area. If a species cannot survive the loss of its habitat, it may become extinct.

Soil loss and flooding

Trees protect the soil from the direct impact of rain, while their roots help hold it in place. Without this protection, soil can be washed away more easily.

Trees and other vegetation also take up rainwater and slow its passage to the ground. When vegetation is removed, more water can reach and flow over the ground quickly, increasing the risk of flooding.

Atmospheric carbon dioxide

Trees take up carbon dioxide from the air for photosynthesis. Removing trees reduces this uptake, so more carbon dioxide remains in the atmosphere, contributing to an increase in atmospheric carbon dioxide.