CONTACT: Thomas J. Givnish, (608) 262-5718; Mark K. Leach, (608) 263-7344
PRAIRIE STUDY DOCUMENTS CATASTROPHIC LOSS OF SPECIES
MADISON _ Surveying the few remaining patches of what was once a vast prairie, scientists have found disturbing evidence that prairie plant species are disappearing at a pace that will all but erase native prairies from the landscape within decades.
The study, conducted by University of Wisconsin-Madison biologists Mark K. Leach and Thomas J. Givnish and to be published Sept. 13 in the journal Science, is important because it provides grim evidence that fragmentation of the landscape by human activities and the disruption of natural processes like fire have dire consequences for prairies and many other ecosystems worldwide.
Leach, an ecologist at the UW-Madison Arboretum, and Givnish, a professor of botany, document a staggering decline in the diversity of native prairie plants in 54 small and scattered tracts of remaining native Wisconsin prairie that were first surveyed 50 years ago by pioneering ecologist John Curtis.
Revisiting old railroad rights of way, country cemeteries and untillable slopes that harbor the last remaining patches of a vast prairie landscape that once covered nearly 2 million acres in prehistoric southern Wisconsin, the UW-Madison scientists found that between 8 and 60 percent of plant species were lost from individual tracts over the last 30 to 50 years.
"It is very serious," says Givnish, a UW- Madison professor of botany. "The rate of loss is catastrophic. We're talking about losing one-half of all species in a remnant prairie in less than a century under the best of circumstances."
In particular, the Wisconsin scientists found that short, small-seeded and nitrogen- fixing plants such as legumes experienced the heaviest losses.
"Short plants are particularly susceptible because they can be shaded out by taller species," says Givnish, "and small-seeded plants have a disadvantage in getting started under conditions of dense growth," a circumstance accommodated by the absence of fire.
"Fire suppression also puts legumes at risk by allowing nitrogen to build up and thereby eliminating the competitive advantage of nitrogen fixers," according to Givnish.
According to Leach, presettlement Wisconsin, and much of prehistoric America, was a fire-swept landscape, and plants and animals in widely diverse ecosystems adapted to regimes of intermittent wildfire.
As the North American landscape developed over the past 200 years and as fires were suppressed or impeded by agriculture and other barriers, trees and non-native plants supplanted those adapted to fire.
"Fire was an important part of many North American ecosystems," says Leach, and many patches of prairie survived into this century only with the help of accidental fires ignited by steam locomotives, the burning of untillable slopes by farmers, and the infrequent maintenance of old country cemeteries.
But with the disappearance of the steam locomotive and the continued and accelerated development of the rural landscape, even those remaining patches are being lost. Of the more than 200 sites originally identified by Curtis in the 1930s and 1940s, many were degraded, and some were outright obliterated by the effects of pesticides and development.
Without protection, restoring new areas and appropriate management, including prescribed burns, those remaining patches will also be lost, says Leach.
"As these habitats become less common, there are fewer species that are going to persist," says Leach. And without fire, many species "are just going to be gone. We won't have them anymore."
_ Terry Devitt, (608) 262-8282, firstname.lastname@example.org