[MCN] Confirmed again: Warmer drier forests can't recover from fire, trees will be replaced

[Lance Olsen]

Excerpt : Rising temperatures are creating a warmer, drier Sierra Nevada climate. Westerling previously showed <http://www.ucmerced.edu/news/2016/wildfire-increasing-west-because-climate-change-research-shows> that these changes are leading to dramatic increases in the frequency, size and duration of wildfires. The new study [https://www.nature.com/articles/s41598-017-02686-0 <https://www.nature.com/articles/s41598-017-02686-0>] suggests that these same changes will make it harder for forests to regenerate, leading to a loss of forest density, with plants better suited to the new climate eventually replacing trees.

“As trees are displaced, the Sierra Nevada will lose its ability to sequester carbon,” Westerling explained. “The plants that spring up in their place will be significantly smaller, making them less effective carbon sinks than the trees they replaced.”

But the carbon stored in forest trees has to go somewhere.

As trees are burned in more frequent wildfires, and as dead trees undergo decomposition, Westerling and his colleagues predict that as much as 73 percent of the carbon in Sierra Nevada forests will be released, resulting in a dramatic spike in atmospheric carbon. This will transform the Sierra Nevada from a carbon sink into a carbon emitter, making the nature-as-polluter scenario a reality.

Westerling and his collaborators note that their predictions are actually conservative. The effects might be more extreme than their models suggest.

“Our study does not account for a number of factors that might influence the dynamics of forest carbon,” Westerling said. “However, the factors we ignored are likely to accelerate the loss of forest. Our predictions likely underestimate the severity of actual effects.”

http://www.ucmerced.edu/news/2017/study-wildfires-climate-change-could-make-sierra-polluter <http://www.ucmerced.edu/news/2017/study-wildfires-climate-change-could-make-sierra-polluter>
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“Serious thresholds are crossed when forests convert to vegetation types without trees 
and, as a result, lose valued forest ecosystem services. ”
 
Constance I. Millar and Nathan L. Stephenson. Temperate forest health in an era of 
emerging megadisturbance. Science  21 August 2015
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"… the race between climate dynamics and  climate policy will be a close one …."

Hans Joachim Schellenhuber. “Global warming: Stop worrying and start panicking?” 
Proceedings of the National Academy of Sciences 2008
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“Now we have a way of dividing America.”

Newt Gingrich

Quoted in Greider, William 
Who will tell the people. (p. 276)
1992.  Simon & Schuster

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