How does deforestation affect biodiversity?

Forests contain some of the richest concentrations of biodiversity on the planet. But between 1990 and 2020, around 420 million hectares of mainly tropical forest has been lost and  a further 10 million hectares, an area the size of Scotland and Wales combined, is being lost each year. Without the shelter, food and water the forests supply, the many thousands of species that coexist within and beneath the canopy of trees also vanish. 

Forests are home to a huge array of different tree, amphibian, bird and mammal species but they are facing a combination of threats. The Amazon – the world's biggest rainforest – has an estimated 15,000 species of trees, an estimated 3,000 species of fish in the river system and there are currently 1,300 described species of birds. But about 17% of it has been deforested.

Logging for timber and the clearing of tropical and subtropical forests to make way for agriculture and grazing are the two main causes of destruction to forest habitats. Fire is also a major threat to forests. In rainforests such as the Amazon, fire is usually used to clear land for farming. 

Much of the tropical and subtropical forest that remains around the world has become fragmented, with 20% of global forest scattered across 34 million smaller patches affecting species that require large territories, but also increasing the isolation of animals and plants, limiting their gene pools.

Despite the huge annual losses caused by deforestation, there have been some improvements in keeping some parts safe. Some tropical rainforests, subtropical dry forests and temperate oceanic forests are now located within protected areas, including indigenous reserves, with studies showing these are often capable of slowing deforestation.

Forest loss does not simply mean all biodiversity is wiped out, but it often results in a significant change in the mix of species that live there since some species will thrive while others will be lost. So-called generalist species such as some deer, foxes and white storks have been seen to increase in forests that have been disturbed by human activity. Small, light -loving plants can also flourish in cleared patches of forest.

To find out more: Amazonia’s future: Eden or degraded landscapes? | Royal Society; Past and future decline and extinction of species | Royal Society