Fire: Friend and foe
Thirteen years ago, I witnessed a new, hard-edged ecology that operates in the West. I was sitting in the stands of our small rodeo arena, watching irritated bulls throw off a succession of young men like so many rag dolls, when a bolt of lightning ripped the sky, striking the juniper-clad ridge across the valley. The next day, as the winds whipped up, a smoldering tree erupted into a crown fire that raced across several thousand acres.
When the smoke cleared, the geography of the fire-burned land was as plain to see as a missing piece of jigsaw puzzle: A forest had become an open desert.
The Bureau of Land Management dropped seed on the site that fall, and by the following year, some grasses had re-established themselves. The most ubiquitous species, however, was one the agency had not sown and had hoped to exclude: Cheatgrass, a Eurasian import that thrives on fire and is green for only a few weeks in early spring, quickly took over the burned area and has remained there ever since.
Will a forest ever return to our ridge? Probably not in my lifetime, because cheatgrass has altered its ecology. That fact was driven home last summer, when another lightning strike set off a cheatgrass-fueled fire in the original burn area, killing native shrubs and trees trying to regain a foothold and reinforcing cheatgrass's dominance.
Western ecologists - and this publication - have argued vigorously that we must embrace fire to restore our native ecosystems. It's an attractive idea, particularly given that efforts to suppress fires over the past century have provided the fuel - in the form of dense stands of trees and shrubs - for the fires that now burn so ferociously. But to simply embrace fire without considering the new ecological context humans have created via the introduction of exotic plants and pests is naive. Today, fire can lead as often to ecological conversion as to restoration.
That's certainly the case with Arizona's Sonoran Desert, where, as Michelle Nijhuis reports in this issue, an African native called buffelgrass has rapidly spread into the cactus-studded hills surrounding Tucson and Phoenix. Like cheatgrass, buffelgrass thrives on - and fuels - fires that are lethal to native flora. Despite the valiant efforts of dedicated buffelgrass pullers, the Sonoran Desert of the future will likely look more like a dry African savanna than a desert.
So, should we go back to our Smokey Bear mentality and put out every fire we can? No. By now we know that there is no cookie-cutter approach to maintaining healthy native ecosystems. Fire will happen in the West, no matter what we do, and fire thoughtfully marshaled can reinvigorate our forests, particularly at higher elevations.
But exotic species are here to stay, and keeping them from overrunning native ecosystems will require a multipronged strategy, including fire suppression, the judicious use of herbicides, and, ironically, the intentional planting of other exotics. In Utah, researchers were excited to discover that a plot of rangeland planted with an Asian shrub after a 1984 blaze remained unscathed when this summer's massive Milford Flat Fire passed through, the Salt Lake Tribune reports. Forage kochia is not only fire-resistant; it spreads slowly, competes well with cheatgrass, and provides shade and stable soils for native plants.
Fighting exotics with other exotics does not have the clean-edged ecological appeal of, say, letting a lightning-caused fire just do its thing. But in this complex battle, we need to look at every tool available.