Samplings: October 2009

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False-color satellite images—taken in 1992, left, and 2006, right—show how deforestation changed one swath of central Brazil.

NASA

Deforestation of Brazil’s Amazon Basin for cropland, grazing, and lumber has held relatively steady at its late-twentieth-century peak of around 7,000 square miles per year. Yet even if that rate remains constant, the resulting annual emission of carbon dioxide into the atmosphere will actually increase, say researchers at the Carnegie Institution for Science in Stanford, California.

Carbon release from deforestation is a function of the area cleared, the felled vegetation’s biomass, and the fate of its carbon. To calculate the area and biomass, Scott R. Loarie and two colleagues studied satellite images that were collected between 2001 and 2007 and validated by on-site inspections. Then they estimated emission rates based on how much of the cleared vegetation is typically removed, burned, left to rot, used as lumber, or converted to charcoal.

The team found that the southeastern rim of the basin, cleared mainly in the 1980s and 1990s, was relatively low in biomass. During the 2001–2007 study period, deforestation moved northwest into denser forest with taller trees—and it’s heading for acreage with higher biomass still. Consequently, carbon dioxide emissions rose steadily during the study period, and could rise yet another 25 percent above the study-period average—with increased risk for the climate. (Geophysical Research Letters)

Related link:
Asner Laboratory for Regional Ecological Studies