underestimated. Gaston et al. (1998) measured actual biomass, based on an inventory and population density, and compared that to the expected biomass based on the biophysical characteristics of that area. The analysis showed a larger amount of carbon loss due to degradation than to deforestation. Brown further presented analyses from Malaysia that suggest deforestation is focused in areas with a lot of accessibility and fragmented landscapes (Brown et al., 1994). The loss of biomass in Malaysia is mostly from the removal of big trees, which can represent 30 percent of the biomass per hectare.
Several focal areas were presented for reducing uncertainty in estimates of tropical forest carbon fluxes. Brown suggested that better and more frequent assessments of carbon stocks and land use change be developed for vulnerable areas, with less emphasis on obtaining full coverage. Coarse resolution remote sensing may also be able to identify vulnerable areas for deforestation, while spatial models may be able to further identify drivers (e.g., access, fragmentation) of forest degradation. Brown also stated that more research to identify historical land use patterns and quantify forest degradation and fragmentation are needed to better understand changes in tropical forest carbon stocks.
Most of the work on indirect effects in tropical forests has utilized modeling (e.g., CO2 effect studies by Tian et al., 1998; McKane et al., 1995; Potter et al., 1998). However, there have been a few experiments measuring carbon fluxes over different time frames in the Amazon. To resolve the uncertainties of indirect effects, Brown suggested the need for experiments on tropical forests to assess the effects of temperature, CO2 enrichment, and nutrient deposition. Because half of the world’s tropical forests are secondary forests, Brown suggested that experiments focus on them because the greatest indirect effects of CO2 fertilization will be there. She also suggested that the network of older forest plots be expanded and that the ages of forest plots be more accurately determined.