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Fires in the forest

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Fires in the forest

Postby balzaccom » Sun Jan 27, 2019 12:59 pm

I often participate in the High Sierra Topix discussion boards, and a retired NPS ranger there has posted some really thoughtful comments on the fires that have ravaged California. Here is an excerpt:

"I just went back and reviewed some data analysis I did a few months ago, now adding the Camp Fire. There’s a great data set of all fires in California since, roughly, about 1900 – and some before. I did a search for fires over 50,000 acres. Arbitrary but I think it captures the large catastrophic fires. In the Sierra, there are 14 fires of that size. ALL have occurred since 1995. Roughly the same is true of the rest of the state though there’s several of that size in Southern California before ’95.

I then used a vegetation data set to get the percentage of conifer vs. non-conifer fuels the Sierra fires started in and burned in. All but 1 (and I’ve not yet done the Camp Fire) started in brush/oak/grassland. The majority fuel (>50%) they burned in was the same, not coniferous forest.

The point of that exercise is to emphasize that these are not ‘forest fires’ and, while I have nothing against logging, the belief that increased logging will somehow stop fires is just wrong. Just today, Trump threatened to cut off FEMA money because California does not manage our forests adequately. A complete misunderstanding of the situation. If you look at satellite images of many of these fires where they do burn through forest, you’ll easily see they burn right through large tracts of clear cuts without those open areas affecting rate of spread. After all, even if you cut the trees, you still get brush growing in so nothing is gained.

Note, I’m really open to anyone checking my work here. Although I’m pretty good with GIS, I’m not fully confident my data choices and conclusions mean what I think they mean… .

Next: so what? The discussion here started by a swipe at Jerry Brown for using fire “to again bolster his global warming narrative.” On two important points, Jerry is correct to have brought it up. First, it is the responsibility of a politician to faithfully advocate for solutions to critical problems of the people he or she represent. Here, there is a solid argument backed by solid science that human-caused climate change contributes to, among other things, an increase in the severity of wildfires.

Second, it’s also the responsibility of leaders to use the best science to arrive at solutions to those critical problems. Again, Jerry Brown is correct to draw attention to anthropogenic climate change as a problem that can be mitigated by active measures by the people he represents, such as conservation of resources, restoring ecological health to wildland, and other such efforts directed or suggested by our elected representatives.
Several here provided links to current peer-reviewed papers to support this. Notably Impact of anthropogenic climate change on wildfire across western US forest. The summary:


Significance
Increased forest fire activity across the western United States in recent decades has contributed to widespread forest mortality, carbon emissions, periods of degraded air quality, and substantial fire suppression expenditures. Although numerous factors aided the recent rise in fire activity, observed warming and drying have significantly increased fire-season fuel aridity, fostering a more favorable fire environment across forested systems. We demonstrate that human-caused climate change caused over half of the documented increases in fuel aridity since the 1970s and doubled the cumulative forest fire area since 1984. This analysis suggests that anthropogenic climate change will continue to chronically enhance the potential for western US forest fire activity while fuels are not limiting https://www.pnas.org/content/113/42/11770

Other papers back this premise up. That’s not at all to say there aren’t other critical factors that drive these recent (since ’95) fires. Some researchers speculate that the very long period that fire has been suppressed from ecosystems has created huge areas of contiguous high fuel loads. In pre-Euro-American times, fire was either started by Native Americans or by lightning. Because they were mostly low-intensity ground fires, they created a mosaic of open areas among the forest. When burning through forest, they’d burn the lower 10 feet or so of fuels – the “ladder fuels” that carry fire into the forest crown.

It’s possible that by the late 20th century a combination of more extreme weather brought on by climate change and the fuels (aka forest, chemise & oak woodland) became contiguous with equivalent fuel loads. No open areas to stop or slow down a fast-moving fire driven by the extreme weather events (low relative humidity, high temperatures, high wind) that are the signature predication of climate models.

And here is a link to the original post---and the rest of the discussion: http://www.highsierratopix.com/communit ... 2&start=60
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balzaccom
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