Deforestation`s double blow: carbon emissions and biodiversity loss

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Deforestation increases CO2 emissions, as forests are subjected to 'slash and burn' clearing to make way for agricultural land. In China, for example, vast areas of rainforest are being cleared to make way for rubber plantations. Using satellite images, researchers have assessed that the average loss of natural forest between 1976 and 2003 is 13,722 hectares per year. In total, this caused a loss of biomass carbon stocks of 80 Teragrams (Tg)1 of carbon by 2003. This land-use change is also destroying natural habitats, with important consequences for forest biodiversity.

China is currently the world leader in afforestation, but these efforts hide pockets of significant deforestation and replacement of natural forest with plantations. The Xishuangbana forest, for example, is home to the highest level of biodiversity in China. However, by 1976 this forest area had already shrunk by 70 per cent. Deforestation, to make way for rubber plantations, is leading to increased carbon emissions, as carbon stored as plant biomass is released back into the environment as CO2. Loss of habitats and species is a further consequence in this region.

Researchers have coupled satellite imagery with 'on the ground' forest data, and estimated that the current rate of deforestation in the Xishuangbana area is 1.12 per cent annually. The increasing demand for rubber and a series of national Chinese policies are driving deforestation in this region. If deforestation continues at the current rate for the next 20 years, the total forest cover in the region will decrease to 24 per cent, with an annual loss of 0.2 Tg of stored carbon per year.

The researchers proposed a forest recovery scenario to prevent continued loss of carbon stocks from this region, while continuing to allow rubber plantations to expand. For example, only establishing rubber plantations in areas of shifting cultivation (a form of agriculture in which the cultivated area is changed regularly, allowing soil properties to recover) below 1500m would reduce the impact of new rubber plantations on carbon stocks. Stored carbon could also be increased by converting grasslands and shrublands back into forest areas. Such young aged stands would contribute to carbon sequestration for the next 40-80 years. Additional carbon sequestration could be achieved by promoting agroforestry practices as an alternative to slash and burn farming. This might include establishing tea plantations in the understory beneath rubber plantations, which would also reduce soil erosion. These practices could also promote habitat development to encourage biodiversity. The researchers also suggest that, in the future, quantification of biomass change could be improved by performing an increased number of long-term surveys, over larger forest areas.

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