Net flux of carbon dioxide from tropical forests in 1980

Deforestation in the tropics is responsible for an annual net release of carbon to the atmosphere, estimated for 1980 at between 0.5 and 4.2 × 1015 g (refs 1-6). By comparison, the release of carbon from combustion of fossil fuels was 5.2 × 1015 g in 1980. The wide range of estimates for the tropical biota and soils has been due primarily to different estimates of the rate of deforestation2,7. A recent assessment of the world's tropical forests by the Food and Agriculture Organization/UN Environment Program8,9 provides a comprehensive, country-by-country survey of deforestation in the late 1970s as well as estimates of the volumes of wood in tropical forests. The assessment thus provides an independent data base, perhaps the most reliable to date, from which terrestrial releases of carbon to the atmosphere can be calculated. Here we compare the FAO/UNEP survey with other sources of data on rates of deforestation and stocks of carbon in the tropics; then we present the calculated net flux of carbon between tropical forests and the atmosphere based on these different data; and, finally, we consider the accuracy of current estimates of the net biotic flux. © 1985 Nature Publishing Group.