Carbon sequestration in tropical Asia: an assessment of technically suitable forest lands using geographic information systems analysis

Tropical forest lands hold the greatest promise for sequestering large quantities of carbon. In thls study, an analysis was performed to produce a first order map of the technical suitability of present-day forest lands to sequester additional carbon in the continental part of tropical Asia. The analysis used a geographic information system (GIS) approach to assess the difference between 2 indices of potential and actual carbon sequestration of forests on a regional scale. This difference represents the degree to which forest biomass has been reduced (degraded) from its potential maximum caused by the long history of human impacts on the landscape. The difference indicates the relative amount of new biomass carbon which could be added to particular areas of land if they were protected, free from human disturbance, so that they could accumulate biomass up to their potential with no social, economic, or political constraints. A potential carbon sequestration index (PCSI) map was derived Iron1 d GIS lllodel bdsed on cii~lldtic d ~i d yev~~lorphological factors. The actual carbon sequestration index map was derived via 2 methods: a degradation approach based on population densities and climate zones, and a remote sensing approach based on a 4 yr mean of the noinialized difference global vegetation index derived from NOAA AVHRR satellite imagery. Despite limitations, the methods provided reasonable maps of regional technical suitability on which to budd as data quality and methodologies improve. Areas of highest techn~cal suitability included the lowland moist and lowland seasonal ecofloristic zones, closed forests, and Peninsular Malaysia and India. On average, the technically suitable present forest lands could sequester an additional ca 90 Mg C ha-' in aboveground biomass.