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Mignon: Last week's Science magazine featured an article about global warming and wildfires. The study's lead author, Dr. Anthony Westerling, an assistant professor to the University of California – Merced, reports that his team used forest service reports of wildfires to look at trends over the last 30 years or so. Westerling found that whereas prior to 1987 there weren't a lot of wildfires, the area burned since 1987 was about six times as much as that burned before 1987, and that these forest fires could be fueling climate change.
When looking into the causes of the increase in wildfires, they found that in some cases land management issues were important, like the Ponderosa pine areas in the western United States, but in other places like the northern Rockies, especially above 7000 feet, land management wasn't such a big issue. Here's Dr. Westerling:
Westerling: Well, there is in a sense a tipping point: the melting point of water, ice.
Mignon: The researchers found a specific effect during warm years.
Westerling: In these warmer years you have this large area that melt out earlier than before and the soils dry out sooner, and the vegetation is dryer, and you have a longer dry season, and you have more opportunities for fires to ignite, and you have more combustible fuel.
Mignon: They also say that forest fires release the carbon into the atmosphere that is usually sequestered by the vegetation. So the increase in forest wildfires could cause a positive feedback loop for global warming.
Westerling: So as the frequency at which the forest burn increases, then at least initially that results in more carbon being released.
Mignon: Changes in the kinds of plants in the forest can also cause problems.
Westerling: And then as the forest composition changes – there are fewer trees and less dense forests – you'd expect that to have an effect on average carbon uptake in those forests from year to year. So in this instance it seems likely that the continued increase in temperature would result in more carbon in the atmosphere and less in the forest, which would be a positive feedback loop.
Mignon: Dr. Westerling concludes that the increase in temperature causes an increase in forest fires which leads to more carbon dioxide being released into the atmosphere and also a reduction in the types of vegetation that are good at storing carbon dioxide.
Dr. Westerling's comments were made available courtesy of Science Magazine.
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