Forests have gained a lot of attention in the climate change conversation because of their ability to suck carbon out of the atmosphere. Individuals can buy "reforestation" offsets on the internet. There's talk of including credits for carbon stored in trees and wood products as part of many proposed cap-and-trade systems. Cities and businesses are even planting trees as part of their efforts to slow climate change. But forest ecosystems are, by their nature, unpredictable. And new research shows carbon sinks are weaker than predicted.
There's no doubt that forests, and their tremendous ability to store carbon, can play a role in protecting the climate. But we have to be cautious about that role. Forest ecosystems are, by their nature, unpredictable -- - there's simply no way to know how much carbon a forest will store over the long haul. Worse, climate change itself magnifies those uncertainties. If a warmer climate makes forest fires more frequent -- as some people believe is possible -- then a lot of "offsets" will simply go up in smoke. Or consider BC's devastating pine beetle infestation -- an example of how ecosystem disruption can fell more trees than any chainsaw.
And there's troubling news today that makes us more cautious than ever: A new global study by researchers at the University of Helsinki shows that trees are absorbing less CO2 than predicted, as the world warms and vegetation patterns shift.
It turns out that changing growing seasons may decrease the seasonal window when vegetation is a sink -- taking in carbon -- rather than extending that season. That means plants are providing less sinks at the same time they gain time to be CO2 sources.
The Guardian reported the study's main points today:
- The ability of forests to soak up man-made carbon dioxide is weakening, according to an analysis of two decades of data from more than 30 sites in the frozen north.
- The finding means that more of the CO2 we release will end up affecting the climate in the atmosphere rather than being safely locked away in trees or soil.
- The results may partly explain recent studies suggesting that the amount of CO2 in the atmosphere is increasing faster than expected.
- If higher temperatures mean less carbon is soaked up by plants and microbes, global warming will accelerate.
Climate scientist John Miller of the University of Colorado put it this way (PDF) in his commentary on the study for the journal Nature: "We are currently getting a 50 percent discount on the climatic impact of our fossil fuel emissions." (That is, half of what we pump out is sucked up by the oceans and ecosystems on land.) "Unfortunately, we have no guarantee that the 50 percent discount will continue."
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Biodiversivist Posted 10:32 am
04 Jan 2008
In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world
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Kit Stolz Posted 10:34 am
04 Jan 2008
"When scientists started monitoring the breathing of this stand of hemlock trees, they suspected any carbon dioxide captured by new growth would be canceled out by carbon dioxide released from decaying old trees. This is one of the oldest parts of Harvard Forest. Unlike other sections, it was never cleared for agriculture but was used instead as a woodlot. Some of the trees are 300 years old.
But the measurements delivered a surprise. The hemlocks capture a lot more carbon from the air than they give up: about a ton more, per acre, per year.
Equally surprising is the carbon's destination: "Only about half of the carbon that gets pulled out of the atmosphere is going into wood," says Hadley. "The rest must be going into the soil."
Other places in this forest, where the trees are younger, have been capturing even more carbon. And Steven Wofsy, the scientist at Harvard who pioneered the monitoring techniques used here, says at the site that he's watched the longest (17 years), the forest has been soaking up carbon faster and faster.
"That is a real mystery," he says. "We know where it's going, but we don't know why. We're trying to unravel that. It's one of the big questions in climate science.""
http://www.npr.org/templates/story/story.php?storyId=1733 ...
Suspect this may be one of those science stories that resists easy conclusions.
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Biodiversivist Posted 10:41 am
04 Jan 2008
In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world
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Erik Hoffner Posted 10:45 am
04 Jan 2008
"When scientists started monitoring the breathing of this stand of hemlock trees, they suspected any carbon dioxide captured by new growth would be canceled out by carbon dioxide released from decaying old trees.
But the measurements delivered a surprise. The hemlocks capture a lot more carbon from the air than they give up: about a ton more, per acre, per year.
Equally surprising is the carbon's destination: "Only about half of the carbon that gets pulled out of the atmosphere is going into wood," says Hadley. "The rest must be going into the soil."
Other places in this forest, where the trees are younger, have been capturing even more carbon. And Steven Wofsy, the scientist at Harvard who pioneered the monitoring techniques used here, says at the site that he's watched the longest (17 years), the forest has been soaking up carbon faster and faster."
http://www.npr.org/templates/story/story.php?storyId=1733 ...
Not saying there's no merit to the study that's the subject of this post, but that this question is an awful lot bigger than just one piece of research.
Erik
The Orion Grassroots Network: 1,100+ grassroots groups working for conservation & more
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Erik Hoffner Posted 10:49 am
04 Jan 2008
The Orion Grassroots Network: 1,100+ grassroots groups working for conservation & more
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Sam Wells Posted 2:13 pm
05 Jan 2008
Fortunately, when the sun shines photosynthesis occurs in the reverse, creating sugars from carbon dioxide and emitting oxygen. Some numbers are heard were that for the average tree, three times as much CO2 is absorbed instead of emitted during respiration. Juvenile trees are much higher in proportion and very old trees and about even-Steven.
But such generalizations fall apart if one examines different regional, different tree types, and effects of environmental impacts such as increased ambient CO2 and nocturnal temperature. One study seems to claim that as night-time temperatures rise, growth-related respiration increases rapidly. Other studies purport that trees in the Amazon is growing faster, producing more oxygen, and absorbing more CO2 than ever on a per-tree basis (e.g., lower respiration rates than expected).
My intuition tells me that higher night-time temperatures and a prolonged drought would only increase CO2 levels from trees, thereby off-setting any environmental benefit as to CO2 reduction. Water is a key ingredient in photosynthesis and transporting sugars about the tree's organs. Therefore, the tree would utilize more stored sugars during a drought and respire much more, 24 hours a day. Not that I know much more than a layman, but a fascinating topic for naturalists. /sammie
Onward through the fog
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Delay And Deny Posted 4:09 am
06 Jan 2008
Anthropogenic Global Warming is sounding more and more to me like those 19th century "aethers" that physicists used to talk about. Whenever you read some Royal Academy scientist going on about a discovery, they always throw in something about the cause being an "ineluctable aether".
So too global warming.
Here's a very simple story. Trees are absorbing less CO2 because of warming.
Now, an ordinary person would say "oh, well that's why the CO2 keeps rising...because whatever is causing the warming is affecting the trees and the result is more CO2".
But no. Not the Grist Ecologists. They have to throw in the AGW aether and invent a roundabout reason to blame Man for the whole thing and somehow make it a feedback loop without ever proving causality.
My Log
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Sam Wells Posted 4:57 am
06 Jan 2008
But I must admit, beyond the science which has shown serious doubts about trees being "carbon sinks" over the last decade, it just doesn't make any sense to give credits for planting trees - because we're cutting down the forests as fast as we can! How can we give a CO2 credit for 50 acres of new trees when 500 acres of trees were bulldozed down at the same time, and another 500 went down due to diseases and pests?
Give me a break. /sammie
Onward through the fog
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