According to the Food and Agriculture Organisation of the United Nations 2005 statistics, global deforestation, mainly due to conversion of forests to agricultural land, continues at a rate of 13 million hectares per year. At the same time, forest planting and natural expansion of forests have reduced the net loss of forest area. The net global change in forest area in the period 2000-2005 is estimated at -7.3 million hectares per year (an area about the size of Panama or Sierra Leone), down from -8.9 million hectares per year in the period 1990-2000.
Estimates from the Intergovernmental Panel on Climate Change (IPCC) suggest that tropical deforestation is currently responsible for about 20 per cent of anthropogenic carbon dioxide emissions. Only approximately one-twentieth of this is offset by reforestation in temperate regions. Tropical forests act as a significant carbon sink, helping to limit the rate of rise of atmospheric carbon dioxide to less than 50 per cent of the rate of emissions. Removal of rainforests weakens this buffering and exposes us more to the effect of our emissions. An accelerated rise of carbon dioxide from both an increased source and a weakened sink implies an accelerated rate of global warming.
Rainforest destruction also affects climate through changes in other greenhouse gases, organic soot particles and through processes such as water recycling, which have local and global impacts. For example, rainforest loss can increase the concentration of ozone, another greenhouse gas.
Aerosols are released by burning forests and can modify temperature and local rainfall regimes. Rainforests recycle rain water back to the atmosphere, which maintains their own moist climate and also affects neighbouring regions; deforestation can modify atmospheric circulation and rainfall across the globe.