Felling of Tropical Trees Has Soared, Satellite Shows, Not Slowed as UN Study Found

The rate at which tropical forests were cut, burned or otherwise lost from the 1990s through the 2000s accelerated by 62 percent, according to a new study which dramatically reverses a previous estimate of a 25 percent slowdown over the same period.  That previous estimate, from the U.N.'s Food and Agriculture Organization's (FAO) Forest Resource Assessment, was based on a collection of reports from dozens of countries.  The new estimate, in contrast, is based on vast amounts of Landsat image data which directly record the changes to forests over 20 years.

"Several satellite-based local and regional studies have been made for changing rates of deforestation [during] the 1990s and 2000s, but our study is the first pan-tropical scale analysis," explains University of Maryland, College Park, geographer Do-Hyung Kim, lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

Kim and his University of Maryland colleagues Joseph Sexton and John Townshend looked at 34 forested countries which comprise 80 percent of forested tropical lands.  They analyzed 5,444 Landsat scenes from 1990, 2000, 2005 and 2010 with a hectare-scale (100 by 100 meter) resolution to determine how much forest was lost and gained.  Their procedure was fully automated and computerized both to make the huge datasets manageable and to minimize human error.

They found that during the 1990-2000 period the annual net forest loss across all the countries was 4 million hectares (15,000 square miles) per year.  During the 2000-2010 period, the net forest loss rose to 6.5 million hectares (25,000 square miles) per year -- a 62 percent increase is the rate of deforestation.  That last rate is the equivalent to clear cutting an area the size of West Virginia or Sri Lanka each year, or deforesting an area the size of Norway every five years.

In terms of where the deforestation was happening, they found that tropical Latin America showed the largest increase of annual net loss of 1.4 million hectares (5,400 square miles) per year from the 1990s to the 2000s, with Brazil topping the list at 0.6 million hectares (2,300 square miles) per year.  Tropical Asia showed the second largest increase at 0.8 million hectares (3,100 square miles) per year, with similar trends across the countries of Indonesia, Malaysia, Cambodia, Thailand and the Philippines.  Tropical Africa showed the least amount of annual net forest area loss.  Still, there was a steady increase of net forest loss in tropical Africa due to cutting primarily in Democratic Republic of Congo and Madagascar.

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