The Great Lakes Zephyr - Wind Energy & Hydrogen Journal

FOR IMMEDIATE RELEASE
6/9/2004
CONTACT: Don Waller, (608) 263-2042, dmwaller@wisc.edu; Thomas P. Rooney, (608) 265-2191, tprooney@wisc.edu; David A. Rogers, (608) 262-2593, darogers@students.wsic.edu

STUDY PORTRAYS CREEPING ‘IMPOVERISHMENT’ OF STATE’S FORESTS

MADISON — Tramping parcel after parcel of Wisconsin’s north woods, botany researcher David Rogers is finding less and more.

There are fewer native species in fewer numbers in some places. There are more exotic species almost everywhere. And in some places, some native species, in reaction to human-induced change, are beginning to behave like pernicious exotics, crowding out other native species and reducing the overall diversity of plant life on the forest floor.

Rogers, a University of Wisconsin-Madison graduate student, is retracing the steps of John T. Curtis, the botanist best known for his comprehensive surveys of Wisconsin plant life, and for his seminal book, The Vegetation of Wisconsin.

Fifty years ago, the late Curtis and Grant Cottam, fellow UW-Madison botany professor, surveyed the north woods, cataloging the enormous diversity of plant life under the forest canopy. The work conducted by Cottam and Curtis on the state’s northern highland plateau in the early 1950s gives Wisconsin an ecological baseline that exists in few other places in the world.

“The original purpose of their survey was to describe the vegetation of the state,” says Thomas Rooney, another UW-Madison botany student who, with botany Professor Don Waller and Rogers, have resurveyed 62 of the original Curtis and Cottam sites in northern Wisconsin. The study was conducted with the support of the National Science Foundation.

The team’s findings, published in the June 2004 issue of the journal Conservation Biology, paint a bleak picture of the steady decline of forest plant biodiversity.
Among the team’s findings:
* The average site lost nearly 20 percent of its native flora from 50 years ago.
* Species diversity declined at 45 of 62 sites surveyed.
* Found on only one site 50 years ago, exotic species have now colonized two-thirds of the sites resurveyed.
* Plant generalists, whether exotic or native, are replacing more specialized plants, reducing biological diversity in the forest.
* Plants that depend on insects for pollination are disappearing faster than plants that have developed other ways of dispersing pollen.
* Areas where hunting is restricted, such as state parks and natural areas, are faring the worst as deer populations grow unchecked.
* Indian reservations, with longer hunting seasons and better overall forest management, have not only experienced less loss of biodiversity, but have gained species since the original surveys of 50 years ago.

“What we are seeing is that things are slowly changing. We’re slowly starting to lose a lot of things that make forests interesting,” says Rooney. “It’s not a crisis situation — but it’s not good.”

The new study is important, according to Waller, because it is among the first to quantify what many conservation biologists believe is the sixth and latest mass extinction event in the history of the Earth. The decline of species is so gradual, he says, that it passes unnoticed over the course of a human lifetime, and only with the help of such baseline studies as the ones conducted by Curtis and Cottam can biologists today take stock of what’s changing.

“Things are vanishing before our eyes,” says Waller. “The natural world is getting less interesting.”

Primary among the causes of eroding biodiversity, the botanists say, are the spread of exotic plant species and the state’s booming deer herd.

Fifty years ago, the exotics were absent from all but one of the 62 sites. The new survey found exotics such as orange hawkweed, Kentucky bluegrass and hemp nettle at 43 sites. Although the non-native plants have yet to reduce the richness of native plant species, the study warned that it may only be a matter of time before foreign plants begin to pose a far more serious threat to native flora.

“These are the shock troops,” Waller says. “They represent the leading wedge of the invasion.”

The study implicates the white-tailed deer as “a key driver of ecological change in this region.” Rates of species lost, the study notes, were highest at sites without deer hunting.

“The smoking gun we have at the moment is the high density of white-tailed deer,” Waller says.

That finding suggests that researchers and land managers need to pay much more attention to the interactions of deer and other animals in an ecosystem. Changes imposed by one animal, for example, can have a “cascade effect” that influences many other animals and plants.

“Decline in relative abundance of animal-pollinated and animal-dispersed species, particularly in protected areas and areas without deer hunting, suggest that a systematic shift in guild structure is underway,” the Wisconsin botanists write. Plants especially at risk include the bluebeard lily, wild sarsaparilla, sessile bellwort and bishop’s cap.

The study concludes that the systematic decline in forest species richness is a signal that “existing conservation efforts in the region are insufficient or ineffective. Together, these results suggest that a major and largely unacknowledged wave of biotic impoverishment is sweeping temperate forests throughout North America.”

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Terry Devitt, (608) 262-8282, trdevitt@wisc.edu




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