Amazonian devastation: Common sense quantified to predict disaster

July 05, 2002

Threats to Amazonian forests are no news, but a team led by William F. Laurance of the Biological Dynamics of Forest Fragments Project and the Smithsonian Tropical Research Institute pinpoints specific causes of forest destruction in hopes of stemming the tide. Human population density, distance to the nearest highway and dry season severity best predict the extent of deforestation, the group reports in a Journal of Biogeography article released today.

Human populations in the Amazon have grown from about 2.5 million in the 1960's to more than 20 million today. The dramatic influx of settlers has been encouraged by government activities designed to accelerate economic development in the region and to attract private capital.

The Amazon basin sustains nearly 60% of the world's remaining tropical rainforest and plays a vital role in maintaining biodiversity, regional hydrology and climate and terrestrial carbon storage. It also has the world's highest absolute rate of deforestation. In Brazilian Amazonia, which represents about 70% of the basin, deforestation rates since 1995 have averaged the equivalent of seven football fields per minute (nearly 2 million ha per year).

In this analysis of forest cover data from 1999 National Oceanic and Atmospheric Administration imagery, soil fertility and waterlogging had little value as predictors of deforestation. Soil depth was only marginally significant. Distance to the nearest river, or the nearest road, were far less significant than distance to the nearest highway.

According to Laurance, "our findings predict that current policy initiatives designed to increase immigration and dramatically expand highway and infrastructure networks in the Brazilian Amazon will have important impacts on deforestation activity. Deforestation will be greatest in relatively seasonal, south-easterly areas of the basin, which are most accessible to major population centers and where large-scale cattle ranching and slash-and-burn farming are most easily implemented."

Under the auspices of its Avança Brazil (Advance Brazil) program, the Brazilian government intends to invest over US$40 billion in highways, railroads, gas lines, power lines, hydroelectric reservoirs and river-canalization projects to criss-cross large expanses of the basin, greatly increasing accessibility to remote frontier areas.

However, the article emphasizes "...the potentially dire losses of Amazonian forests projected by recent studies are not yet a fait accompli. Pressure from the international community and from foreign investors (which provide significant financial support for Avança Brazil and other Amazonian development initiatives) can strongly influence development policy, planning and environmental assessment in Brazil. Cooperative resource-management programs supported by wealthy nations and non-governmental organizations can also have major environmental benefits. Such efforts are crucially needed to ensure that Amazonian forests are not irreversibly degraded in the coming decades."
ref. William F. Laurance, Ana K.M. Albernaz, Gotz Schroth, Philip M. Fearnside, Scott Bergen, Eduardo m. Venticinque and Carlos DaCosta. Predictors of deforestation in the Brazilian Amazon. Journal of Biogeography, 29, 737-748.

The Biological Dynamics of Forest Fragments Project, Manaus, Brazil, seeks to answer questions about plant and animal relations, the biology of extinction, the process of forest regeneration, and the effects of forest edge and fragmentation on the genetic structure of tropical species.

The Smithsonian Tropical Research Institute, headquartered in Panama City, Republic of Panama, is one of the world's leading centers for research on the ecology, behavior, and evolution of tropical organisms.

Smithsonian Tropical Research Institute

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