Landsat satellite imagery covering the entire forested portion of the Brazilian Amazon Basin was used to measure, for 1978 and 1988, deforestation, fragmented forest, defined as areas less than 100 square kilometers surrounded by deforestation, and edge effects of 1 kilometer into forest from adjacent areas of deforestation. Tropical deforestation increased from 78,000 square kilometers in 1978 to 230,000 square kilometers in 1988 while tropical forest habitat, severely affected with respect to biological diversity, increased from 208,000 to 588,000 square kilometers. Although this rate of deforestation is lower than previous estimates, the effect on biological diversity is greater.

Carbon fluxes from tropical deforestation and regrowth are highly uncertain components of the contemporary carbon budget, due in part to the lack of spatially explicit and consistent information on changes in forest area. We estimate fluxes for the 1980s and 1990s using subpixel estimates of percent tree cover derived from coarse (National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer) satellite data in combination with a terrestrial carbon model. The satellite-derived estimates of change in forest area are lower than national reports and remote-sensing surveys from the United Nations Food and Agriculture Organization Forest Resource Assessment (FRA) in all tropical regions, especially for the 1980s. However, our results indicate that the net rate of tropical forest clearing increased ≈10% from the 1980s to 1990s, most notably in southeast Asia, in contrast to an 11% reduction reported by the FRA. We estimate net mean annual carbon fluxes from tropical deforestation and regrowth to average 0.6 (0.3–0.8) and 0.9 (0.5–1.4) petagrams (Pg)⋅yr ⁻¹ for the 1980s and 1990s, respectively. Compared with previous estimates of 1.9 (0.6–2.5) Pg⋅yr ⁻¹ based on FRA national statistics of changes in forest area, this alternative estimate suggests less “missing” carbon from the global carbon budget but increasing emissions from tropical land-use change.

Degradation by logging, fire, and fragmentation is increasing as a spatially distinct disturbance in the Amazon landscape.

D. L. Skole, W. H. Chomentowski, W. A. Salas, A. D. Nobre; Physical and Human Dimensions of Deforestation in AmazoniaIn the Brazilian Amazon, regional trends a