ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Friday, September 13, 1996 TAG: 9609130141
SECTION: NATL/INTL PAGE: A-7 EDITION: METRO
DATELINE: WASHINGTON
SOURCE: Associated Press
By building dams to prevent floods and by fighting wildfires, Americans could be endangering plant and animal species that thrive on ecological benefits natural disasters bring, say two new studies.
Researchers reporting in today's edition of the journal Science based their findings on two separate instances of changing natural phenomena to protect people and property:
* Blocking periodic floods that used to rage in California deprived the state's steelhead trout of food.
* Fourteen percent of the plants that once thrived in Wisconsin's prairie preserves vanished in the last 50 years because wildfires no longer clean out stronger competitors.
Certainly people can feel immediate benefits from preventing natural disasters, acknowledged ecologist David Tilman of the University of Minnesota in analyzing the research.
But their efforts may have ``unintended long-term costs'' because natural disasters have ``unexpected, cascading consequences on the abundance of many species,'' Tilman wrote. ``A seemingly pristine river that has been dammed or a forest or prairie remnant that is inadvertently protected from fire is not being preserved.''
Ecologists have long concentrated on the direct impacts of environmental changes on a single, often endangered, species.
If logging a particular area was wiping out an animal, for example, the recommendation might be to preserve some timber stands.
But some scientists now argue that's too narrow an approach - and not just for preserving plants and animals. The Midwestern floods of 1993 that wiped out whole towns, Tilman notes, were exacerbated by dikes that eliminated river flood plains that for centuries had acted as a ``natural safety valve.''
The new research examines how environmental changes alter the total habitat.
First, University of Chicago ecologist Timothy Wootton examined the steelhead trout that feed on aquatic invertebrates in northern California rivers.
The main casualty of flooding was a predator-resistant species of caddis fly, a bottom-dweller with a heavy shell that gets crushed by the rocks and debris of a flood. Flooding wiped out enough of the caddis fly population to strengthen the lower food chain and give trout more food, Wootton discovered.
He compared rivers that were dammed to prevent flooding with naturally flowing waters and found the rivers that didn't flood had significantly more predator-resistant invertebrates that the trout simply couldn't eat.
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