Boreal Forests Found to be Net GHG Emitters
by Jeremy Elton Jacquot, Los Angeles on 11. 2.07
The last few months have witnessed a flurry of debate in the scientific literature over the relative merits of using forests as carbon sinks to combat global warming. The broad-based consensus seems to be that, yes, trees can work - if planted in the right areas - but also that we shouldn't hang our hopes on them.
The latest salvo in the debate comes from Tom Gower of the University of Wisconsin, who has determined that Canada's boreal forest - far from hindering global warming's advance - may be spurring it on by releasing more GHG than it absorbs. "The boreal forest, at least in the north-central part of Manitoba, has gone from a weak carbon sink to a weak carbon source. It is now contributing to atmospheric (carbon dioxide) concentration," he said.
Using a one million sq. km stretch of forest in Manitoba, Gower and his colleagues coupled their measurements of how carbon moved between the atmosphere and the trees with past records and computer models to examine how the forest's ability to store carbon dioxide has changed since mid-century. Their results showed that the forest's ability to store more carbon dioxide than it emitted had weakened over the last few years - to the point where it has now become a net emitter of carbon.
The culprit for this abrupt reversal, Gower explained, is forest fires. "The warmer climate has increased fire frequency and extent. Those wildfires have caused this transition in the boreal forest from a carbon sink to a carbon source." They have, in effect, caused a positive feedback loop: the more soil is exposed to sunlight as a result of trees burning, the speedier the decomposition process and the more carbon dioxide is released.
The real concern is that climate change may soon causing the large-scale thawing of permafrost around the world; second only in size to tropical rainforests, boreal forests cover a vast swathe of land in the upper latitudes of Alaska, Siberia, China, Scandinavia and the Yukon.
Gower's assessment is fairly grim, to say the least: "Based on our current understanding, fire was a more important driver than climate was. But if carbon dioxide concentration really doubles in the next 50 years and the temperature increases four to eight degrees Celsius, all bets may be off."
Via ::The Canadian Press: Boreal forest may be net greenhouse gas emitters, new study suggests (newspaper)
See also: ::Does Cutting a Tree Create Greenhouse Gas?, ::By the Numbers: The Boreal Forest
Image courtesy of 416style via flickr
Forests everywhere are NET carbon sinks. This study didn't contradict this statement. It actually verified it. The growth of forests stores carbon - that simple. The BURNING of forests releases carbon. The study clearly states that the reason for boreal forests releasing more carbon than is being stored is because there are large numbers of fires. This doesn't in anyway subtract from the fundamental point that forests in boreal locations store carbon dioxide. It's as silly as saying that banks don't work because last year there was more money lost through bank robbers than money deposited by customers. Forests store carbon. Stop the fires.
"Forests everywhere are NET carbon sinks. "
No. The posted study shows that statement to be incorrect.
Fires are part of forest. Fires occur. Fires occur even when humans are not involved.
Your statement is correct only we if exclude part of 'reality'.
(How many banks would survive if they lost more money via theft than they gained via deposits? Think about it. Reality sucks, eh? ;o)
If we harvest and maintain the forests correctly they'd be even better carbon storers. Once the wood is put into a building or other product it'll hold onto the carbon for years.
'No. The posted study shows that statement to be incorrect...Fires are part of forest. Fires occur. Fires occur even when humans are not involved...Your statement is correct only we if exclude part of 'reality'.'
---First, it is obvious that fires occur naturally. I am not contradicting this obvious fact. Fires occurred naturally in that section of Canadian forest that Gower studied BEFORE 1950. But nevertheless, those forests were still storing carbon at a steady clip - even though forest fires occurred naturally, occassionally. The fact that fires occur naturally on rare occassions does NOT mean that forests are incapable of being NET carbon sinks. And this doesn't take a rocket science degree. If forests were long-term NET emitters of carbon, there simply would NOT be any boreal forest - period. The fact that they have been and continue to be NET carbon sinks is evidenced by the fact that there are millions of trees and woody vegetation - carbon stored over time into solid form. It is simple, if you are seeing a forest you are seeing the results of long-term carbon storage - not of long-term carbon emission.
Second, climate change has led to hotter conditions which have made the forests more susceptible to catching fire and to spreading. However, the overwhelming majority of forest fires do not occur naturally. I live in a heavily forested area of Spain. Spain has more severe problems with forests drying out and catching fire than Canada or northern Europe. Global warming has made forests in Spain much, much more likely to catch on fire and to spread quickly. I had part of the forest on my finca burn a few years back because of this. However, well over 90% of forest fires are started either directly or indirectly by the hand of man. Even though Spanish forests are much more susceptible than decades back, it almost always STILL requires some human irresponsibility to trigger a fire to start. My finca burned because some a****e decided to burn some garbage at the local waste dump which was 6km from my finca. Two years back a fire that reached some 5km from my finca was started by a careless barbequer. Even though warming has weakened forests, it is still extremely difficult here in Spain (so even more so in Canada) for a fire to start by itself. It is HUMANS causing the burning of the forests - NOT nature. It is NOT natural.
Third, because the virtual totality of forest fires in Spain are NOT natural but rather are caused by man, the Spanish govt. has spent tons of money, time and resources to 'exclude this part of reality' - the human trigger. It has spent millions on ad campaigns to sensitize citizens toward their responsibilities to ensure that they don't cause fires. It has spent much money on survaillance systems to catch pyromaniacs that like to start forest fires. It has toughened the laws to make it more difficult for developers to get away with burning forest in attempts to get land reclassified. It has passed laws making it illegal to smoke in public parks or to make any type of open fires from April to October. It spends money to keep the edges of roadsides clean of brush to ensure that smokers who flick their cigarette butts out car windows don't cause fires (this used to be a significant reason for fires). And the list goes on and on. The Spanish govt. has done and continues to do everything it can think of to 'exclude this part of reality.' And the number of square kms burned every year in Spain diminishes every year even though global warming keeps making Spanish forests more and more susceptible to fires. It is NOT nature causing so much fire damage that forests end up emitting more carbon than capturing - it is MAN. It is completely possible to greatly reduce human-induced fires. So I will say again what I said before: Forests everywhere are NET carbon sinks. Fires are the problem (as the study explicitly stated). Stop the fires.
'How many banks would survive if they lost more money via theft than they gained via deposits?'
---None would survive if this happened continously year in and year out. But in the US west, we all know that some 150-200 years ago banks were being robbed left and right. Did the US western banking system collapse and disappear? No. The govt and the banks found solutions to eliminate the scourge of bank robbers - just like the Spanish govt. is now finding ways to deal with the scourge of human-triggered forest fires. And just like the US west was eventually able to bring the problem of bandit bank robbers under control so that their banks could flourish, national govts. can bring under control the human-triggering of forest fires so that forests can continue to flourish naturally - and continue to be the net carbon sinks they have always been and will continue to be.
Think about it. ;o)