Recent analyses of land-use change in the tropical regions and in the temperate and boreal regions of the earth were combined to yield a global estimate of 1.0 - 2.6 times 1015 g C for the net release of carbon to the atmosphere in 1980 from changes in land use. Deforestation in the tropics accounted for nearly all of the flux; the net release of carbon from temperate and boreal regions was only 0.1 times 1015 g C. The average global value of 1.8 times 1015 g C in 1980 was distributed geographically among tropical countries and other regions on the basis of deforestation rates and carbon stocks.

The net release of carbon from changes in land use worldwide is inconsistent with the results of geochemical models of the carbon cycle. The discrepancy is smaller than in previous analyses, but is large enough to exceed the errors of the analysis. Possible explanations for the discrepancy include the possibility of a net accumulation of carbon in undisturbed ecosystems as a result of CO2 fertilization or changes in climate. Even if the terms of the global carbon equation were to appear balanced at present, current knowledge is insufficient to predict whether terrestrial ecosystems will act as a positive or negative feedback on the anticipated CO2-caused global warming.