Saturday, May 23, 2009

Do wildfires eat their veggies?

Scientists expect global warming to have an array of consequences. The increase in temperature will make wildfire-prone areas dryer. Coupled with more extreme weather, this sounds like a recipe for wildfire disasters. Last year, wildfires sent California into a budget crisis because the state badly underestimated the costs. It seems like the line at the end of The Terminator is appropriate to describe the state of wildfires in the American West: "a storm is coming."

But, a recent study coming out of Montana State University suggests that this storm might not be as bad as we expect. Research by MSU post-doc Philip Higuera suggests that Mother Nature may adapt to the warmer weather in a way that leads to fewer wildfires than we're anticipating. As the climate warms, Higuera and his colleagues predict the types of vegetation to change. As the vegetation changes, the types of plants that remain will be more resistant to fires.

In particular, shrubs are quite flammable, whereas deciduous trees are fire-resistant. Warmer weather leads to fewer shrubs and more deciduous trees. Over the last 10,000 years, the temperature has fluctuated orders of magnitude more than in the last 20 years. Higuera used coal deposits from northern Alaska to look at these 10,000 years of data. In his study, Higuera observed that as the climate got warmer, the vegetation looked more leafy and less shrubby. As a result, the vegetation was less conducive to burning.

This is interesting and encouraging because my own research suggests that in the absence of vegetation change, the cost of wildfires is escalating and escalating quickly. In a working paper, my co-authors and I estimate that, by year 2025, it will cost $23 million more to protect houses from wildfires in Montana alone.

If Higuera's findings are right, our estimate of these additional costs is high. On the other hand, Higuera himself says that when estimating the costs of wildfires, "You wouldn't be wrong if vegetation doesn't change." I don't know how much vegetation would need to change to avert the higher costs we predict, but I doubt that 15 years gives Mother Nature enough time to convert Montana's forests into fire-resistant trees.

Regardless of the magnitude of these effects in the short term, the long-term implication is that Mother Nature is surprisingly resilient. We can be glad to have Mother Nature on our side!

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