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Why Is the Boreal Forest Breathing CO2 More Deeply?
http://www.scientificamerican.com/article.cfm?id=boreal-forest-breathes-deep-and-climate-change-pauseWhy Is the Boreal Forest Breathing CO2 More Deeply?
The flow of CO2 into and out of the vast northern forests has been increasing in recent years, thanks to climate change
By David Biello
The boreal forest seems to like the higher levels of carbon dioxide that result from fossil-fuel burning. All that carbon appears to be enabling growth rates not seen in human history for the northernmost forest, according to a new study.
"Boreal forests are more active than 50 years ago," says geochemist Heather Graven of the Scripps Institution of Oceanography, lead author of the new analysis, published online August 8 in Science. She and her colleagues documented a dramatic uptick in the flow of carbon into and out of the forests, which cover most of Canada as well as large swathes of Russia and Scandinavia. "The ecosystems might be changing how much carbon is allocated to different structures, such as leaves, wood or roots, changing their extent or composition, or changing the timing of photosynthesis and respiration as a result of warmer temperatures," she adds.
In the famous saw-toothed Keeling curve depicting increasing levels of CO2 in the atmosphere, the saw-teeth—rising and falling as the Northern Hemisphere breathes in and out with the seasons—have become longer. That is, the difference between low CO2 levels in summer and high atmospheric concentrations at the end of winter have become more pronounced; the amplitude of the change has increased by roughly 50 percent over the last 50 years. Northern forests appear to be taking in more CO2 in summer and releasing more in winter—as shown by Graven and her colleagues who compared atmospheric measurements taken in the far north during and after the International Geophysical Year between 1958 and 1961 with a series of airplane flight measurements taken between 2009 and 2011. All told, at least 32 percent more carbon—an additional 1.3 billion metric tons—moves back and forth between atmosphere and forest, which is roughly two thirds as much as is thought to be stored in boreal forests annually and more than a tenth of the total carbon emitted to the atmosphere by human activity in a year.
Such CO2 ebb and flow suggests that the boreal forest is growing more, although the increase in amplitude is a surprise. Whether this results from more growth overall or growth in response to wildfire or pests remains unclear, but scientists had anticipated that higher levels of CO2, which acts like a fertilizer up to a point, would promote plant growth. As a result, some research has found that portions of the world's deserts have begun to green.
..more..
The flow of CO2 into and out of the vast northern forests has been increasing in recent years, thanks to climate change
By David Biello
The boreal forest seems to like the higher levels of carbon dioxide that result from fossil-fuel burning. All that carbon appears to be enabling growth rates not seen in human history for the northernmost forest, according to a new study.
"Boreal forests are more active than 50 years ago," says geochemist Heather Graven of the Scripps Institution of Oceanography, lead author of the new analysis, published online August 8 in Science. She and her colleagues documented a dramatic uptick in the flow of carbon into and out of the forests, which cover most of Canada as well as large swathes of Russia and Scandinavia. "The ecosystems might be changing how much carbon is allocated to different structures, such as leaves, wood or roots, changing their extent or composition, or changing the timing of photosynthesis and respiration as a result of warmer temperatures," she adds.
In the famous saw-toothed Keeling curve depicting increasing levels of CO2 in the atmosphere, the saw-teeth—rising and falling as the Northern Hemisphere breathes in and out with the seasons—have become longer. That is, the difference between low CO2 levels in summer and high atmospheric concentrations at the end of winter have become more pronounced; the amplitude of the change has increased by roughly 50 percent over the last 50 years. Northern forests appear to be taking in more CO2 in summer and releasing more in winter—as shown by Graven and her colleagues who compared atmospheric measurements taken in the far north during and after the International Geophysical Year between 1958 and 1961 with a series of airplane flight measurements taken between 2009 and 2011. All told, at least 32 percent more carbon—an additional 1.3 billion metric tons—moves back and forth between atmosphere and forest, which is roughly two thirds as much as is thought to be stored in boreal forests annually and more than a tenth of the total carbon emitted to the atmosphere by human activity in a year.
Such CO2 ebb and flow suggests that the boreal forest is growing more, although the increase in amplitude is a surprise. Whether this results from more growth overall or growth in response to wildfire or pests remains unclear, but scientists had anticipated that higher levels of CO2, which acts like a fertilizer up to a point, would promote plant growth. As a result, some research has found that portions of the world's deserts have begun to green.
..more..
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