Burning forests,raging debates

The black-backed woodpeckers drum signals more than the return of life to the forest. It also may be an important clue toward resolving a debate about how much,and even whether,to try to prevent large forest fires.

Scientists are at loggerheads over whether there is an ecological advantage to thinning forests and using prescribed fire to reduce fuel for subsequent firesor whether those methods actually diminish ecological processes and biodiversity.

The US Forest Service,which manages nearly 200 million acres of public land,believes limited thinning and burning will prevent catastrophic wildfires. The approach,developed primarily as a result of tree ring studies,seeks to reconstruct the forests of the West before the 20th century,when the large-scale suppression of wildfire first occurred. Some ecologists and environmentalists,however,are challenging the Forest Services model,saying it is based on incomplete science and is causing ecological damage.

Recent research,they say,shows that nature often caused far more severe fires than tree ring records show. That means the ecology of Western forests depends on fires of varying degrees of severity,including what we think of as catastrophic fires,not just the kinds of low-intensity blazes that current Forest Service policy favours.

They say that large fires,far from destroying forests,can be a shot of adrenaline that stimulates biodiversity.

The black-backed woodpecker could be an important indicator of which side is correct. The bird lives almost exclusively in severely burned forests. It thrives on the fire-chaser beetle and the jewel beetle,which are adapted to fires and can detect heat 30 miles away with infrared sensors under their legs. Tracking the presence of the woodpeckers can indicate whether there are enough severe fires to stimulate their ecosystems and keep their numbers,as well as those of other species,healthy.

For a recent paper in the journal Global Ecology and Biogeography,William Baker,a fire and landscape ecologist at the University of Wyoming,published with Mark Williams,employed an unorthodox method to reconstruct fire history that challenges current analysis of tree rings. Baker and Williams examined handwritten records created by federal General Land Office agents who surveyed undeveloped land in the West in the mid-19th century. Altogether,Bakers students combed through 13,000 handwritten records on 28,000 marked trees and hiked miles in Oregon,Colorado and Arizona to find some of the trees and compare todays conditions with those from the 1800s.

They found that low-intensity fires that occurred naturally were not as widespread as other research holds and that they did not prevent more severe fires. Baker concluded that big fires are inevitable and argues that it is best for ecosystemsand less expensiveto put up with them.

Proponents of the free-fire theory say that widespread wildfires should be viewed as necessary ecological events that reset the clock on a landscape to provide habitats for numerous species for decades to come. This principle stems from research into disturbance ecology. For instance,when a hurricane blows down a large swath of forest or a volcano erupts,it strongly stimulates an ecosystem,scientists have found.

Hutto,the University of Montana ornithologist,said he believes that the Forest Service approach is misguided. He pointed out that morel mushrooms thrive on charred ground,and that birds,including the mountain bluebird and black-backed woodpecker,then move in.

Similarly,a plant called snowbush can remain dormant in the soil for centuries until heat from a fire cracks its seed coat,and it blooms profusely.

The first year after a fire is when the magic really happens, Hutto said.