By Pratap Chatterjee
SAN FRANCISCO, Sep 14 1996 (IPS)

Floods and fires are terrible events that should be prevented at all costs, right? Wrong. New studies published in the latest edition of Science magazine say the benefits may outweigh the damage.

For centuries in the United States, fires swept regularly through the prairies of Wisconsin and floods raged in California. But this changed in the last few decades. Emergency teams have quickly doused fires, while major dams have reduced swiftly flowing rivers to warm, sluggish habitats.

The results have been dramatic: Oak forests now replace the prairies of northern Wisconsin, and farmland dominates the southern part of the state. Dams have diverted water from California’s wetlands into the desert to make it bloom.

But at what cost? Scientists say that the white and pink shooting star flowers that once dotted the prairies have vanished altogether, while the threat of bigger and worse fires is actually increasing.

In California, the steelhead trout is disappearing from the rivers. In other states like Washington, the salmon have vanished altogether from the Elwha in the Olympic peninsula.

“Fires are terribly important, because they allow some plants like the shooting star here in Wisconsin and the ponderosa pine in California to germinate,” says Tom Givnish, author of an article in Friday’s edition of Science, the journal of the American Association for the Advancement of Science.

The studies by Givnish, a professor of botany at the University of Wisconsin at Madison, show that a third of the species in the “pristine prairies” have vanished in the last 50 years. The species most affected were mostly short, with small seeds, as well as legumes that convert nitrogen in the soil.

This study comes close on the heels of suggestions that fire suppression might ironically have been a major cause of the destruction of some 19.4 million hectares of forests so far this year.

Environmental experts explain that the prevention of small fires has prevented the natural thinning of forests. Today, the thicker vegetation burns faster and spreads more quickly, resulting in multi-million hectare damage.

Fires also recycle nutrients to the soil in the form of ash and reduce insect infestations and disease, researchers say. The fresh, green growth after fires also supports deer and other animals.

When these fires are prevented, pine trees give way to spruce, a species far more susceptible to insects and disease.

In California, some 221,000 hectares of Yosemite national park and the Stanislaus national forest burned this year, threatening key areas like the Hetch Hetchy reservoir which supplies drinking water to this city.

Givnish told IPS the major fires that have swept through the chaparral shrub in the mountains of southern California contrast sharply with the small fires just south of the border in Mexico that do relatively little damage.

Studies like those conducted by Givnish have led David Tilman, a professor of ecology at the University of Minnesota in the city of St Paul, to conclude that natural disasters have many benefits.

Tilman warns that the disruption of processes such as floods and fires has “unexpected, cascading consequences on the abundance of many species.” He concludes that the world will be a “markedly different place if we ignore the long-term consequences of our actions.”

Mary Power, a professor of integrative biology at the University of California at Berkeley, agrees, pointing to some of the beneficial effects of floods.

populations of exotic species like bullfrogs that European settlers brought to this state in the nineteenth century from the Mississippi to raise for food,” she told IPS.

But with the building of dams, the incidence of floods has been reduced, allowing bullfrogs to thrive and to decimate the native populations of yellow-legged frogs and turtles.

Dams have also affected other species like the salmon in Oregon and Washington states. In particular, old dams like those on the Elwha river in Washington and the Columbia and Snake rivers in Oregon have prevented saltypically live most of their lives in the ocean but then migrate far inland via the river system to spawn. Dams block their passage and prevent them from reaching their spawning grounds.

Tilman also points out that major river works have not necessarily prevented the worst floods.

A simple example is provided by the huge losses in the midwestern United States caused by the 1993 floods, “which were exacerbated by dikes that eliminated a natural safety valve — the river flood plains,” he writes.

Things hns,” he writes.

Things have changed in recent years, in part because of strong lobbying by environmental groups against the building of dams, demands for the dismantling of large dams, and efforts to allow small, controlled forest fires.

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