Tropical forests and the global carbon cycle: estimating state and change in biomass density

Tropical forests have an important role in the global carbon (C) cycle because of their existing large areal extent, high rates of deforestation, large C pool in vegetation and soil, and high rates of C emissions resulting from conversion to other uses (equivalent to between 22 and 37% of current fossil fuel C emissions) (Table 11.1). Tropical forests currently account for about 43% of the global forest area (Dixon et al. 1994), most of which is in tropical America (52%), followed by tropical Africa (30%) and tropical Asia (18%). They occur mostly as lowland formations where 88% are at an elevation of 1000 m or less. Within the lowlands, 47% are in the rain forest ecological zone, 38% in the moist deciduous zone, and 15% in the dry to very dry zone (Food and Agriculture Organization (FAO) 1993).