Friday, July 07, 2006
Global warming and forest fires
A recent study is trumpeting that global warming has produced dramatically more, and bigger, forest fires in the West than previously.
I am skeptical.
Why?
Because I'd really, really like to know if they took into account the firefighting practices of 100 years ago, extrapolated them into forest growth/tree death rates, and also included population growth and expansion of urban-wild interfaces.
Wally Covington, a famous forestry researcher, claims that forests of 150 years ago were much more open, more thinly populated with trees, than they are today.
Fire suppression practices in the late 19th, early 20th centuries were geared towards just that: suppression. No fire was seen as a good fire.
In an open forest canopy, fires tend to stay in the undergrowth, rather than crowning. Undergrowth fires are slower-burning and spread less rapidly. The undergrowth is burned away, but the trees remain, and various plant life that requires burning to scarify the seeds so the seeds can germinate get that chance to germinate. Also, smaller trees are killed due to the fires, and as the fires happen at intervals, the tree cover in a natural forest tends to top out at different levels, thus keeping crowning fires (which spread rapidly and disasterously) to a minimum (not saying they don't happen, just that they happen less often in an environment like that). The fire suppression policies of the 19th and 20th centuries, by quenching those small fires at all costs, ended up producing forests that are incredibly dense (one estimate talks of going from 40 trees per acre to more than 1000, on average).
Think gardening, and thinning out plants. If you scatter the seed at planting time, it tends to clump up. Most of the seeds will sprout. If you don't thin them out, you'll end up with lots of spindly, thin plants crowded together. Translate this to the forest, and that's what you see around here: "dog-hair thickets", so-called because the trees are tall, spindly, and crowded together--excellent tinder for forest fires.
Then you've got the expansion of the human population, with the urban-wild interface growing rapidly. This means you have more opportunity for just plain idiotic humans to do things like go camping on a weekend (wild forest being easy to get to for a two-day trip, rather than requiring planning and time off for a week's trip) and setting their campfires with the signs that say "Fire danger high! Campfires and open flames prohibited!" (Yes, we did, indeed, have some stupid goober do that a few years ago. He was arrested.)
In a recent discussion of lowlanders not comprehending fire danger, one of my coworkers related following an expensive black BMW on the road down Way Cool Canyon and seeing the driver toss a fully-lit cigarette out the window into the roadside brush during a period of extreme dryness. My coworker took off after him, got in front of him, and stopped his car to get out to harangue him. The driver, nonplussed, said, "I didn't want to get ashes in my car."
Anyway. These two factors mean (1) more opportunity for human-caused fires, and (2) more opportunity for fires to become crown fires, which are by their very nature faster, bigger, and more devastating.
There's a lot of compelling stuff about global warming these days, but on this particular issue I'd like to read more about the study to determine if they were able to take these factors into account.
(While I was trolling about the websites of the various organizations involved in this research, I noticed that the United States Forest Service's Southern Research Station website had one research project listed entitled "Southern Global Change Program". The link was broken. This seems especially interesting given the recent brouhaha about the administration editing research reports and websites...)