MISSOULA, Mont.—U.S. forests offset roughly 11 percent of the nation's industrial greenhouse gas emissions, storing "significant amounts" of carbon that would otherwise pollute the atmosphere, according to new government data.

The findings, released last week, estimate the nation's expanding forests sequester an additional 192 million metric tons of carbon annually due to increases in both the total area of forest land and the amount of carbon stored per acre.

That's the equivalent of removing about half the cars on the roads nationwide, or almost 135 million vehicles.

But as emissions increase and the planet warms, that storage capacity could be compromised, scientists warn.

Warmer summers, changing precipitation patterns and a thinning snow pack are already "aridifying" Western forests, University of Montana Professor Steven Running said during a conference here last week. The combination imperils the health of vast swathes of the western landscape, he warned.

"We think of range as having a 'carrying capacity' - you put too many cows on a pasture and they all get skinny because they don't have enough to eat," he said at a meeting of the Society of Environmental Journalists. "It's the same principle for our forests."

In 40 years, for instance, Montana will likely see 5ºF warmer summers on average but receive 10 percent less rainfall, he said. "We're aridifying our forests."

But for now, the trend in carbon sequestration across the nation is up, according to the U.S. Forest Service data. On average, the agency said, the amount of carbon stored in forestland has increased since 1990.

Wet, temperate conifer forests along the Pacific Coast from Alaska to California store the most carbon - about 93 metric tons of carbon per acre. Arid pinyon-juniper forests of the Southwest store the least - 31 tons of carbon per acre on average.

Forests in the western United States store a greater proportion of carbon in the trees; other areas, such as the Great Lakes, have larger concentrations of peat in the soil, storing more carbon there.

Understanding those differences - and corresponding climate-induced changes - could have important ramifications as the agency assesses the carbon sequestration potential of the nation's forests, agency officials said.

"Forest management on all lands can contribute significantly toward cooling a warming planet," U.S. Agriculture Secretary Tom Vilsack said in a statement. "This new information will assist the public and policy makers as we work to address this significant issue."

DailyClimate.org is a nonprofit news service that covers climate change.

4 Comments

1. 1. Unksoldr 07:40 PM 10/18/10

   The recent NYTimes article about the rich buying up land cheap, is true in the South where I am. Guess what is happening to that land as we speak? Hardwood forests that have been growing longer than the 54 yrs I've been alive, bulldozed to the ground to build McMansion's. Even a real castle not far from here. I don't even want to imagine the destruction of wildlife who just had their homes destroyed. While I a disabled veteran, tries to live on 1k a month in an 90 yr old house. I pray to the Lord of Chaos for a massive CME. It's time to thin the herd quite a bit imho.

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2. 2. docspot 11:36 PM 10/18/10

   If this drivel is true it's amazing that we don't suffocate in the winter. The crap "science", the misanthropy, the class envy, the totalitarian bent of the propnents of this climate hoax is blatant. Chicken Little is not a great role model people.

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3. 3. JVSIRY 05:52 PM 10/24/10

   Climate change due to accelerated combustion of coal, oil and natural gas to meet ever growing transportation and manufacturing needs have also increased between one and two percent annually since the 1990s, so its good there are more forests.
   
   But he fact that soil moisture and spreading arid conditions may curtail what we have planted raises the necessity of reducing carbon emissions (mitigation) and redesigning our buildings to bring more daylighting, and less heat into structures in the warm season and more geothermal heat from the earth into buildings in the winter.
   
   The necessity for urban reforestation is twenty years overdue --efficient solar hot water heating is a 110 year old technology we need to pursue, as Israel has done so remarkably well. There are role models in Germany, Japan, the EU and Australia, if you just take your head out of the sand and recognize that we either pay now to move Inuit and Eskimo villages inland from the arctic, or we pay later to build New Orleans style levees around Wall Street in Manhattan, or copy London in building structures like the Thames barrier on our own tidal rivers.
   
   We still have choices, if we stop blaming one another and pitch-in to reconstruct the coming century in a way that puts people to work using resources more efficiently, curbing the waste, and seeking renewable means to accomplish that tasks industry and municipalities need to get done for our people to thrive, remain healthy and nourish our ecosystem services such as those that thriving forests provide.

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4. 4. JVSIRY 05:55 PM 10/24/10

   Climate change due to accelerated accumulation of heat trapping gases from combustion of coal, oil and natural gas–to meet ever growing transportation and manufacturing needs–have also increased between one and two percent annually since the 1990s, so its good there are more forests.
   
   To correct the initial paragraph above. Thanks

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