Firefighting efforts continue, but the fire grew from around 7,000 acres this morning to 11,000 by tonight. From town, it’s really dramatic; while last year’s Bullock fire sent a haze over the valley, the prevailing wind currently is from the south, so the view from Tucson is of a plume of smoke billowing from the ridge. It’s a big fire; tonight at least two active ends of the fire are visible from town, spread far apart on the spurs of the Catalinas (I had a good view from my roof at dusk, where I fought with a leaky swamp cooler). Heather (with her degrees in biology and range management, her current work in fire science, and her viselike memory of just about everything) and I have talked a lot lately about what this fire ultimately may mean for the Catalinas.
Ponderosa pine communities have a natural fire return interval of around ten years. That is, absent fire suppression, fires tend to burn in these kind of areas every ten years or so, killing saplings that overcrowd the forest and eliminating lots of tinder that, in a context of strict fire suppression, ends up contributing to huge fires like Aspen. In the context of regular fires, native grasses thrive (because they don’t have to compete with thick stands of trees) and produce strong stocks of seeds, and big ponderosas are healthy and spread far apart.
A big, hot fire like the Aspen fire is already taking place in a significantly non-natural context: It has a ton of fuel and burns like crazy because the forest is packed with medium-sized pines and an enormous amount of dry litter. When so much burns, erosion is a serious problem, and some discussion of erosion is already taking place. (After the fire last summer, the monsoon-fed rivers in the mountains ran black (jpg) with muddy ash.) Further, big fires like this disturb plenty of wildlife, but usually at the individual, not species level—that is, while some will be killed by the fire (one commentator on the news this week actually referred to birds parboiling in the trees), many more will flee and survive.
So what happens after the fire? From a purely biological point of view, it’s really interesting that the fire has so far burned somewhat spottily. In Summerhaven, charred foundations sit next to homes that look untouched by flame. In places where ground litter burned and smaller trees were killed, but where soil was not sterilized, grass and herby growth will reappear within a year, healthier than before the fire because competition (for sun, water, and nutrients) with tightly-packed trees will be so greatly reduced. Surviving big trees will similarly be rejuvinated, and aspen stands, previously crowded out by pine saplings, will be resored. New tree growth will be visible in another year or so.
The undeniably positive effects of regular fire are somewhat diminished by the intensity of a great big fire; effects on soils, seed stocks, and wildlife are more up in the air, especially in the short term. In the long term, as has been demonstrated in places like Yellowstone, even huge fires can yield important biological health improvements.
From the human-community-oriented point of view, rebuilding on the mountain may be hard. Lots of houses and cabins there were built on land leased from the Forest Service, and rebuilding loans cannot be taken out against the value of property the occupants don’t own. New construction will have to abide with modern building codes, which may further limit rebuilding because new construction cannot be grandfathered past the current codes. Summerhaven’s infrastructure is said to be pretty old—limited municipal services like water, sewer, and utilities—implicating large-scale facilities re-development as part of the rebuilding.
Finally, when the fire has passed, the results of some homeowners’ efforts to build fire buffers can be assessed, and that will prove really interesting.