Temporal patterns of land-use change and carbon storage in China and tropical Asia

Evaluating the annual sources and sinks of carbon from land-use change helps con-strain other terms in the global carbon cycle and may help countries choose how to comply with commitments for reduced emissions. This paper presents the results of recent analyses ofland-use change in China and tropical Asia. The original forest areas are estimated to have cov-ered 546×10~6 ha in tropical Asia and 425×10~6 ha in China. By 1850, 44% of China’s forests had been cleared, and another 27% was lost between 1850 and 1980, leaving China with 13% forestcover (29% of the initial forest area). Tropical Asia is estimated to have lost 26% of its initial forestcover before 1850 and another 33% after 1850. The annual emissions of carbon from the two regions re-flect the different histories over the last 150 years, with China’s emissions peaking in thelate 1950s (at 0.2-0.5 Pg C·a) and tropical Asia’s emissions peaking in 1990s (at 1.0 Pg C·a). Despite the fact that most deforestation has been for new agricultural land, the majority ofthe lands cleared from forests in China are no longer croplands, but fallow or degraded shrublands.Unlike croplands, the origins of these other lands are poorly documented, and thus add consider-able uncertainty to estimates of flux before the 1980s. Nevertheless, carbon emissions from China seem to have decreased since the 1960s to nearly zero at present. In contrast, emissions of car-bon from tropical Asia were higher in the 1990s than that at any time in the past.