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Want a respite from the noise and drama of the election season? A good way to find some peace and quiet is to step into an old-growth forest, where all stray noise seems to disappear. It turns out, though, that the sense of stasis in these old forests is an illusion - and their dynamics are critically important in our fight against global warming.
Old-growth forests hold vast amounts of carbon from centuries of growth, and this carbon would be released into the atmosphere if the trees were cut down. That much has been known for a long time.
But new research shows that old-growth forests are even more important than previously thought. According to a new study in Nature, old-growth forests aren’t just standing there maintaining the status quo. They are still actively taking up CO2 from the atmosphere.
Checking a long-held assumption
The dominant trees in old-growth forests are about as big as they're going to get. So for a long time, scientists thought that old-growth forests were carbon neutral - that the plants took up as much CO2 from the atmosphere as was released from plant and soil respiration. (To learn about respiration, see this Climate 411 post on agricultural offsets.)
But it's always good to check the numbers, and scientists finally have enough data to start doing just that. The researchers compiled data from 519 studies that reported one or more components of the carbon cycle. Because data for tropical forests were scant, the study included only boreal (northern) and temperate forests.
What the numbers reveal
Their analysis showed that even centuries-old forests are active carbon sinks - they take up more CO2 than they release. In fact, old-growth forests in temperate and boreal zones take up as much as 1.3 gigatons of carbon (Gt C) a year. To put that in perspective, that’s approximately 17 percent of global fossil fuel CO2 emissions in 2005.
It's been estimated that deforestation accounts for 20 percent of current global greenhouse gas emissions. This study adds to the urgency of protecting forests. As the study's authors put it:
The present paper shows that old-growth forests are usually carbon sinks. Because old-growth forests steadily accumulate carbon for centuries, they contain vast quantities of it. They will lose much of this carbon to the atmosphere if they are disturbed, so carbon-accounting rules for forests should give credit for leaving old-growth forest intact.
Fortunately, nations are already discussing how to do this, based on an Environmental Defense Fund plan called Compensated Reduction, and we are working hard to make this a reality. EDF is an active participant in the international negotiation towards a post-Kyoto agreement, and it was great to have deforestation as a major topic at the Bali talks, and the more recent talks in Accra, Ghana, as well.
Further Reading
* All about
deforestation, climate change, and incentives to reduce deforestation.
* Other researchers have tackled the scant information available about tropical forests; they concluded that intact tropical forests also act as carbon sinks
(PDF).
* You can find more posts on climate change science, policy, and news on
Climate 411.