The study, led by environmental nonprofit Winrock International, is the first on the subject to use satellite data. By combining data on gross forest lost and forest carbon stocks to track emissions from 2000-2005, the team arrived at an estimate of 0.81 billion metric tons of carbon emitted per year — approximately one third of previously published estimates. By this accounting, tropical deforestation amounted to just 10 percent of global, manmade carbon emissions during the period.
Emissions were calculated for individual countries, along with a range of statistical uncertainty. Brazil and Indonesia not only produced the most emissions during the period, but together they accounted for 55 percent of all emissions from tropical deforestation.
Nearly 40 percent of all forest loss in the study region was concentrated in the dry tropics, but accounted for only 17 percent of total carbon emissions, reflecting their relatively low carbon stocks in comparison to those found in tropical moist forests.
The team plans to update their work to include the period 2006 to 2010 to assess whether carbon emissions increased or decreased in the second half of the decade.
Combining datasets from different remote-sensing instruments not only permits more detailed analysis than was previously possible, but should also lead to setting more accurate benchmarks for monitoring global carbon emission in the future and compensating nations that work to reduce emissions from deforestation and forest degradation.
The researchers hope the UN takes note of the new data, methods and estimates.
“It’s time to acknowledge the problems with the FAO data and accept that we can now do much better,” said Winrock’s Dr. Sandra Brown, a co-author of the study. “We have the ability, at last, to match the areas of forest clearing with their carbon stocks before clearing in much greater detail, allowing us to pinpoint more precisely where the highest emissions are occurring.”
Satellites contributing data for the study include: the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra satellite; NASA’s Ice, Cloud and land Elevation Satellite (ICESat); NASA’s Quick Scatterometer (QuikScat) satellite; and the joint NASA/U.S. Geological Survey Landsat program.