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Conservation Science for a Healthy Planet

Changing climate could have devastating impacts on forest carbon storage

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May 25, 2017  University of New Mexico  full ScienceDaily article here
Biologists have shown what could be a startling drop in the amount of carbon stored in the Sierra Nevada mountains due to projected climate change and wildfire events.

….roughly half of all human-emitted carbon is absorbed by vegetation and the ocean, and is stored through natural processes — something that helps limit our actual carbon impact on the atmosphere. The problem is, as forests begin to change, due to global warming and large scale fires, the amount of forest carbon uptake will decrease, accelerating the amount of human-made carbon making its way into the atmosphere.

Our simulations in the Sierra Nevada show that the mean amount of carbon loss from the forests under these projections could be as large as 663 teragrams,” said Hurteau. “That’s equal to about 73 percent of the total above ground carbon stock estimated in California vegetation in 2010.”

…The two factors that influence these findings are changes in climate and the likelihood of large scale forest fires. Because California is experiencing warmer and drier conditions due to global warming, certain tree species are not able to flourish across particular geographic regions like they once were. Less tree growth, means less carbon uptake in forests.

The study also shows that wildfires will play a big role in the reduction of stored carbon. And while many of these incidents will occur naturally, Hurteau says we are, in part, to blame for their significance….

…”We’ve been putting out fires for a hundred years, causing tree density to go way up. In the absence of fire that system has a lot more carbon stored in it,” explained Hurteau. “But, when you have these large fire events the amount of carbon stored in the system drops because it kills many of the trees. Whereas, in a forest that’s been maintained by regular forest fires, which is the natural ecological state, your total carbon at any given point in time can be lower but it stays more consistent.”

…Hurteau says researchers have identified strategies for reducing some of the fire risk by actively thinning forests to manage tree density and restoring surface fires. It’s an idea that seems counterproductive until you consider how volatile these ecosystems are due to the risk of large scale fires that end up destroying hundreds of thousands of acres.

…He says it’s not only for the benefit of nature but for all of us, since healthy ecosystems lead to cleaner, better regulated water flow to communities across the western United States.

Shuang Liang, Matthew D. Hurteau, Anthony LeRoy Westerling. Potential decline in carbon carrying capacity under projected climate-wildfire interactions in the Sierra Nevada. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-02686-0

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