Rainforests may store much less carbon than we thought. It could be time to dramatically revise our estimates following the discovery that apparently similar forests hold vastly different amounts of the stuff. The finding is important because there are plans for governments worldwide to compensate tropical countries for protecting their forests as "carbon sinks" to curb global warming. If carbon cannot be counted, then dollars cannot be disbursed.
Greg Asner of the Carnegie Institution for Science in Stanford, California, and colleagues say they used satellite mapping, laser probing of forest undergrowth from aircraft and local ground surveys across a large area of Peruvian rainforest to crack the problem of estimating how much carbon is locked up in forests. But the new technique has revealed a large, previously unknown variability in the density of carbon stored in apparently similar forests.
The Intergovernmental Panel on Climate Change says that there should be about 587 million tonnes of carbon stored in the study area, 43,000 square kilometres of lowland forest in the Madre de Dios region of Peru.
But after dividing the area into 40 million individual grid squares and estimating for each the carbon stored as well as the rate at which it is being fixed and released, Asner says the real figure is just 395 million tones, a third less.
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http://www.newscientist.com/article/dn19408-forest-carbon-stores-may-be-massively-overestimated.html