CO2 is released from fires (red dots) like these near Lake Malawi in southern
Africa in October 2009 for agricultural land clearing. Credit: NASA
Deforestation. The environmental implications of the word are as numerous as the syllables. And scientists like Jim Collatz have the job of trying to ferret out and prove those implications. Or, as the case may be, of correcting what scientists have believed to be true.
When farmers or loggers chop or burn forest land, they set in motion the loss of biodiversity and habitat, as well as soil erosion. Collatz and other scientists are just as concerned — maybe even more so – with the carbon dioxide (CO2) deforested areas contribute to the atmosphere, warming the climate.
In 2005, the U.N. Food and Agriculture Organization announced that forest loss accounts for more than 20 percent of global emissions of CO2 from human activity. If we could stop cutting down trees, some argued, we could make a serious dent in the global carbon problem.
Not so much, a new study in the November 2009 issue of Nature Geoscience suggests. A group of Dutch and American climate scientists, including Collatz, assert that the UN’s estimate of atmospheric CO2 caused by deforestation is substantially overstated – by as much as 40 percent. Recalculating the 2005 figure with updated satellite-based estimates on carbon emissions, the researchers calculated the relative contribution of deforestation and forest degradation to be only about 12 percent.
As a member of NASA Goddard’s Biospheric Sciences research team and co-author of the study, Collatz shared some of his thoughts with us.
What On Earth: How do you account for the change in the share of atmospheric CO2 from forest loss?
Collatz: New emission estimates from tropical deforestation are somewhat lower than in the past. At the same time, fossil fuel emissions are increasing rapidly. Deforestation is becoming a smaller proportion of total human-caused CO2 emissions. So, even if we could stop it completely, it would not be a substitute for decreasing fossil fuel emissions. If deforestation were 20 percent, then decreasing it to 10 percent may be significant and plausible. But since new analysis shows deforestation is closer to 10 percent, it’s unlikely that it can be reduced to zero percent.
What On Earth: What are the implications of your findings?
Collatz: Some might read the paper and argue for less attention toward reducing deforestation. But we need to remain vigilant in this area. Forests provide other valuable services besides storing carbon: biodiversity, food, fiber, water resources, soil resources. Even though current rates of deforestation may be lower than previously thought, vast amounts of carbon are stored in forests and soils all over the globe and are vulnerable to climate change and land management practices. We need to monitor these carbon stocks and manage them for preservation and sequestration, or we may see unexpected increases in atmospheric greenhouse gases that go beyond what is emitted from fossil fuel burning.
To read the full paper on the Web, click here.
–Gretchen Cook-Anderson, NASA’s Earth Science News Team
Correction: Please note the link above to the full paper has been revised. Co-author Robert Jackson of Duke University makes the paper available on the university’s site.