Deforestation and Impacts

Land-use change has driven loss of forests globally and from 2001-2019, 27% of tree cover loss was attributed to deforestation. Since 1900, most deforestation has been occurring in the tropical regions of South and Central America, South-east Asia and Central Africa. Global tree cover loss in the year 2020 was estimated at 25.8 million hectares.

As with temperate deforestation, forest clearance in the tropics occurs mainly due to agricultural expansion, in particular for food and fuel crop growth in Africa and South-east Asia, and cattle ranching in South and Central America. Pressure on the land from mineral mining (to obtain gold, copper and tin), coal mining, and oil drilling is also particularly prevalent in parts of South America, Africa and South-east Asia. Since 2001, a total of 411 million hectares of tree cover has been lost globally.

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Deforestation has many impacts on the climate; the net effect of deforestation in any given location will be determined by how these different impacts combine. Most trees are darker in colour than other surface types which means that they reflect a smaller proportion of incoming solar radiation, having a warming effect on the planet (when compared to more reflective surface types such as grassland). In terms of deforestation, the dark colour of forests means that replacing them with a more reflective surface would have a cooling effect on the climate.

However, trees store a large amount of carbon dioxide and the loss of this store as a result of deforestation, often due to forest fires emitting carbon dioxide, can contribute to a warming of the climate. Over the period 2001-2020, it is estimated that 165 Gt of carbon dioxide has been emitted due to global forest loss. LEAF researchers investigating the warming effect of deforestation in the Amazon found localised warming of the climate to be intensified in areas of greater deforestation. Deforestation also affects the transfer of moisture to the atmosphere which could have substantial impacts on regional rainfall. Interactions between land and atmosphere are particularly important with the climate in South America, with soil moisture found to be key.

The strong link between deforestation and forest fires was illustrated by LEAF researchers in Indonesia. When examining the relationship between tree loss and the occurrence of fire, 70% of the study region was found to have experienced fires within the same year tree loss was observed. LEAF researchers are examining the potential role that protected areas can play in reducing forest loss and fires. You can find out more about our research into forest fires here.

LEAF researchers are exploring the drivers of tropical deforestation in order to inform policy making that will hopefully reduce deforestation in the region. In Tanzania, deforestation rates are high, with more than half a million hectares clearer every year. Researchers working in Tanzania have found small-scale agriculture to be a key driver of the deforestation, although there are often multiple drivers. Reducing deforestation will require strong coordination between land, agriculture, livestock and forest sectors.

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