29 JUNE 2000
As residents of Los Alamos, New Mexico prepare to rebuild houses destroyed by an out-of-control "controlled burn," conservationists worry about restrictions on the use of fire to restore ecosystems.
The charred forest after the Cerro Grande fire in New Mexico this spring. Courtesy Andrea Booher, FEMA photographer
Until about a century ago, large areas of the American West burned periodically in wildfires ignited by lightning. But Smokey the Bear's campaign against forest fires may be working too well: Dousing every fire results in an enormous buildup of fuel.
Today, wildfires may be less frequent, but they're hotter and far more destructive.
Ironically, the New Mexico blaze was started by a fire set to reduce the fuel load in Bandelier National Monument, just south of Los Alamos, the atomic bomb's birthplace. The theory is that after a controlled burn, cooler, less destructive fires can be allowed to burn, and the woods would become more hospitable to the fire-tolerant native creatures.
Seriously snoozing!
Still, the torching of 493 homes and charring of 43,000 acres of forest in New Mexico was a major setback for the idea of using controlled burns to reduce fire danger and restore habitat. "I'm concerned that we're all going to pay for the sins of others in terms of using fire as a management tool," says Bruce Haak, a biologist with the Idaho Department of Fish and Game. Haak is monitoring controlled burns designed to prevent the extinction of the Northern Idaho ground squirrel.
The Northern Idaho ground squirrel, marked with a short-acting dye, is slightly larger than a chipmunk. Fewer than 1,000 remain in the world. Courtesy Paul Sherman.
Even the fans of the threatened squirrel know the itsy-bitsy animal has a PR problem: It's only about 9 inches long. It's rare - fewer than 1,000 live on a patch of land about 20 miles on a side. And because that land ranges from 3,800 to 5,200 feet, the squirrel spends 240 days per year in a hole in the ground, hibernating beneath the snow.
It may be little, but this critter is in big need of friends. While its population was estimated at 5,000 in the 1980s, a recent computer model predicted that it would go extinct by 2006. Being picky helps explain why the squirrel is one of the most endangered mammals in North America: It prefers open meadows with downed trees for protection, runways and observation points. Eating primarily grass seed, it avoids deep woods, which can hide predators like coyotes and hawks.
Back when
When Paul Sherman, a neurobiologist at Cornell University, set out to study the squirrel in 1985, he was shocked that almost nothing was known about it. Intriguingly, one scientist thought it was a social animal, meaning that it lived in cooperative colonies.
As Sherman started filling in the blanks, he realized that the squirrels were actually quite solitary. They live in groups only because of the rarity of their preferred habitat tends to concentrate them into patches of meadow.
As Sherman joined forces with Thomas Gavin, a conservation biologist at Cornell, they observed that the overall population of the Idaho ground squirrel was declining, and individual populations were disappearing entirely.
Cornell biologist Thomas Gavin with encroaching trees that have isolated Northern Idaho ground squirrels into postage-stamp-size habitat.
Courtesy Paul Sherman.
Arms outstretched, Gavin gestures to the trees within 10 meters on both sides of him. Why? Genetic analysis indicated that different populations of ground squirrels had been mixing genes until about a century ago. Then, about the time that fire suppression began, the interbreeding stopped.
A second problem was nutrition: Surviving animals were not gaining enough weight. Given the squirrel's hibernation-heavy schedule, it should at least double in weight between emerging from its burrow in April and hibernating in July or August, says Haak.
Historical records indicated that as fires grew rarer, the landscape was filling in with ponderosa pines. That change could play several roles in the rodent's vanishing act:
Little squirrel food grows under the pines, so the expanding forests crowd the squirrels into small patches of meadow.- For fear of predators, squirrels will not enter the forest. Restricted to mating with neighbors alone, inbreeding becomes likely.
- Similarly, the expanding forest prevents squirrels from recolonizing habitat where, for whatever reason, they no longer live.
Burn, baby, burn
If the problems stem from the absence of fire, the logical solution was to return fire to the ecosystem. It's a solution that's being adopted at ecological restorations nationwide.
The National Forest Service, whose Payette National Forest houses the squirrels, has begun burning patches ranging from three to 15 acres in size. Crews first fell larger pines and let them dry. The fires are set in the fall, when the squirrels are safely burrowed several feet below ground. With no houses in the area and plenty of roads giving access to fire trucks, Haak says the small burns are easy to control.
It's too early to tell for sure if the fires are helping the squirrels, but some initial signs are positive. Due to reseeding and fire damage to woody species, the vegetation springing up after a burn often includes some of the vanishing bunch grasses that the squirrels prefer. "After the site has been burned, there's a flush of herbaceous plants, very succulent, doing very well," says Gavin.
Acting squirrelly
A site called Summit Gulch (who concocts these names, anyway?) is what Haak calls the "poster child" for the project. The 12 squirrels present last year have grown to 26, which are packing on the pounds. "The animals are extremely healthy; even the yearlings at this population are larger than adults of other populations," Haak says.
Despite the signs of progress, conservationists who use fire to restore prairies and forests worry about getting burned by the Los Alamos disaster. Ironically, the concern comes at a time when scientists are in almost unanimous agreement about the importance of fire in ecosystems adapted to it.
"Fire is as important to the ecosystem as rain or snow," says Sherman. "It's one of the major forces of nature. Because of lightning, fire has been part of the ecosystem [in Idaho] for millions of years. The proof is how many plants and animals have evolved to deal with fire. "The Los Alamos legacy is troubling, Sherman admits, for the tragic disruption of people's lives, but it's only a small part of a larger picture. "There are thousands of controlled burns every year, and they don't have this result. Still, what sticks in our minds is this disaster." It's only natural that a human disaster will be memorable, but the context is equally important. "This was a set fire that caused the catastrophe," Sherman says, "but every summer - just last week in Colorado - you had natural fires occurring that are burning down houses - and for the same reason. There's too much fuel on the ground."
David Tenenbaum
Bibliography
• Paul Sherman et al, Journal of Mammology, V. 80, No. 1, pp. 156-68, 1999.
• Los Alamos Smoke Clears to a Town Feeling Burned, Julie Cart, Los Angeles Times, P. A1, June 18, 2000.
Related Why Files
• Wildfires
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Endangered Species
