Rare is the forest untouched by man. Whether logging or clearing land for agriculture, the bulk of the world's forests have fallen to crops, cattle or younger trees. According to some estimates, less than 10 percent of forests worldwide can be considered old growth, or undisturbed for more than a century. And that is not just a tragedy for the plants and animals that require mature forests—it is also a tragedy for the world's climate, according to a study published today in Nature.

Laborious research in the 1960s by the late pioneering U.S. ecologist Eugene Odum seemed to indicate that forests achieve a balance between the amount of carbon dioxide (CO₂) absorbed by growing trees and plants and the amount of CO₂ released back into the atmosphere by the decomposition of dead plant matter.

But it seems that old forests may be more efficient than previously believed. Biologist Sebastiaan Luyssaert of the University of Antwerp in Belgium and his colleagues surveyed all the existing measurements of how much carbon is absorbed and released from old-growth forests (exclusively in temperate and boreal forests due to a lack of extensive data on tropical forests). Their findings, Luyssaert says: "old-growth forests continued to accumulate carbon."

In fact, not only do old trees continue to store carbon in their wood, forest soils also appear to be actively capturing carbon over time, although direct observations of this process are lacking. All told, by Luyssaert's calculations the relatively small remaining stands of old-growth forests in the U.S. Pacific Northwest as well as Canada and Russia consume "8 to 20 percent of the global terrestrial carbon sink," or roughly 440.9 million tons (0.4 gigatonnes) of carbon per year.

That is not even close to enough to balance the 1.8 billion tons (1.6 gigatonnes) released into the atmosphere by deforestation or crop-clearing. But it remains important—if unrecognized—in the present battle to combat climate change. Luyssaert suggests that credit—and money—should be given to protect such old-growth forests under carbon trading schemes and other economic mechanisms to combat climate change.

"Any kind of existing program that gives credit to reforestation could give credits to forest preservation," such as the carbon offsets based on tree planting, he says. "Instead of investing the money in a new forest, it could as well be used to protect an old forest."

But the case for old forests as carbon sinks is not airtight. The measurements used by Luyssaert rely on the flux of CO₂ levels over the forest, but this kind of metric can be skewed by young stands of trees within an old-growth forest or an increase in growth as a result of higher atmospheric carbon dioxide levels, according to forest ecologist Mark Harmon of Oregon State University in Corvallis, who was not involved in the study.

"To really test this, one would need a far better data set that had different ages in the same system: that is very young, mature, old-growth and super old-growth in each system," he says. But "older forests should not be written off as places to store more carbon. Even if they aren't taking up more carbon, their harvest releases a great deal."

It remains unclear whether tropical forests, such as those of the Amazon or Congo, produce the same effect, due to much faster decomposition of dead plant matter in these climes. But preliminary results suggest they do. "The data that are available show that, like the boreal and temperate forests, tropical old-growth forests also continue to take up and sequester carbon," says forest scientist Eugenie Euskirchen of the University of Alaska Fairbanks, who was not involved in this research.

Protecting old-growth temperate and subpolar forests might prove a boon to the fight against global warming, also because of the soils they currently shade. "Many old boreal forests tend to be underlain by permafrost soils, which can contain many times more carbon than that stored in the vegetation," Euskirchen notes. Melting those soils is an ongoing climate calamity.

6 Comments

1. 1. Vinayaraj V R 01:20 PM 9/11/08

   It clearly shows the importance of keeping old forest intact and away from human activities. There should be no compromise. Let me quote another article.
   
   "A study on the role of natural forests in carbon storage has found that unlogged natural eucalypt forests in Australia's south-east store about 640 tonnes of carbon a hectare, while intact old-growth forests in Victoria and Tasmania store up to 1200 tonnes a hectare."
   
   Read that here.
   
   http://www.canberratimes.com.au/news/local/news/general/carbon-huddles-deep-in-the-forest/1235063.aspx
   
   Thanks
   Vinay
   http://cmonletsplantatree.blogspot.com/
   

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2. 2. candide 03:07 PM 9/11/08

   If that's true we are doomed.
   
   That would also explain the doubters and current administrations lack of attention - it's pointless.

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3. 3. Digavobis 05:51 PM 9/12/08

   This article doesn't stress the importance of reforestation. There are many parts of the World, that have been striped of any trees, such as the Himalayan mountains. The foothills of Mt. Everest used to be dense forests, but every last tree has been cut down, for firewood. We are talking about many thousands of acres. Reforest this land, and many other areas like this. The Himalayan people know how to make fire, but they don't know how to make firewood. If private industries don't take up the task, governments need to. This is a great area to recruit volunteers. Another problem is the Oregon governor will not permit intelligent forest management, such as thinning, and cleaning up the undergrowth, in forests, which help feed forest fires. He would rather save one tree, and let 10,000 acres burn to the ground, from a lightning storm. Where does say that politicians are smarter than the scientists, and forest management experts? I know that most businesses can't be trusted. They are more interested in, whats in it for them today, and not much interested in the future. Leave it for the people, in the future, to figure it out. just like our Social Security System.

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4. 4. romby in reply to Digavobis 05:50 AM 9/14/08

   Totally agreed!

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5. 5. farrer 10:14 PM 10/1/08

   Guess the only solution to global warming is to completely reforest all the first world countries??? Or move everyone into the first world countries and let the existing forest take over??? It's always easy to sit in your nice house, car and office and tell the folk in the forest to live in the forest forever... Why aren't you doing it as the solution? Your pre-historic ancestors did.

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6. 6. Escher99 08:21 PM 9/25/09

   California has gone ahead with a policy that allows clear cut logging of forest that is sold for carbon credit. It unfortunately ignores your findings in this article and it undermines California's position as a leader on reducing global warming gasses. It is also a perfect case study in talking tough but leaving the logging industry in the drivers seat. Lo and behold, California now allows loggers to double dip - selling land for carbon credits before clear cutting.

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