Annual fluxes or carbon from deforestation and regrowth in the Brazilian Amazon

The distribution of sources and sinks of carbon among the world's ecosystem s is uncertain. Some analyses show northern midlatitude lands to be a large sink, whereas the tropics are a net source(1); other analyses show the tro pics to be nearly neutral. whereas northern mid-latitudes are a small sink( 2,3). Here we show that the annual flux of carbon from deforestation and ab andonment of agricultural lands in the Brazilian Amazon was a source of abo ut 0.2 g C yr(-1) over the period 1989-1998 (1 Pg is 10(15) g). This estima te is based on annual rates of deforestation and spatially detailed estimat es of deforestation, regrowing forests and biomass. Logging may add another 5-10% to this estimate(4), and fires may double the magnitude of the sourc e in years following a drought(4), The annual source of carbon from land-us e change and fire approximately offsets the sink calculated for natural eco systems in the region(5,6). Thus this large area of tropical forest is near ly balanced with respect to carbon, but has an interannual variability of /- 0.2 PgC yr(-1).