Biologists seek answers to grizzly bear migration roadblocks
Chris Servheen spends a lot of time mulling a serious scientific question: Why didn't the grizzly bear cross the road? The future of the...
The New York Times
SALTESE, Mont. —
Chris Servheen spends a lot of time mulling a serious scientific question: Why didn't the grizzly bear cross the road?
The future of the bear may depend on the answer.
The mountains in and around Glacier National Park teem with bears. A recently concluded five-year census found 765 grizzlies in northwestern Montana, more than three times the number of bears as when it was listed as a threatened species in 1975. To the south lies a swath of federally protected wilderness much larger than Yellowstone, where the habitat is good, and there are no known grizzlies. They were wiped out 50 years ago to protect sheep.
One of the main reasons they have not returned is Interstate 90.
To arrive from the north, a bear would have to climb over a nearly 3-foot concrete Jersey barrier, cross two lanes of road, braving 75- to 80-mph traffic, climb a higher Jersey barrier, cross two more lanes of traffic and climb yet another barrier.
"It's the most critical wildlife corridor in the country," said Servheen, grizzly-bear recovery coordinator for the federal Fish and Wildlife Service, of the linkage between the two habitats.
As traffic grows beyond 3,000 vehicles a day, crossing a road becomes extremely difficult. The 13 miles of Interstate 90 in this area, where grizzly bears most likely would cross, has 8,000 to 10,000 vehicles a day, and so is impermeable much of the time. And it is not only bears — wolves, wolverines and a host of other species roam the region.
In recent years scientists have come to understand the marked changes brought by the roads that crisscross the landscape.
Some experts believe that habitat fragmentation, the slicing and dicing of large landscapes into small pieces with roads, homes and other development, is the biggest of all environmental problems.
"By far," said Michael Soule, a retired biologist and founder of the Society for Conservation Biology. "It's bigger than climate change. While the serious effects from climate change are 30 years away, there's nothing left to save then if we don't deal with fragmentation. And the spearhead of fragmentation are roads."
Fragmentation cuts off wildlife from critical habitat, including food, security or others of their species for reproduction and genetic diversity. They eventually disappear.
Some 4 million miles of roads affect 20 percent of the country, and in the past 10 years the new field of road ecology has emerged to study the many impacts of roads, and how to mitigate the damage.
"Roads are the largest human artifact on the planet," said Richard T.T. Forman, a professor of landscape ecology at Harvard, who brought road ecology from Europe to the United States. He is the editor of the definitive text on the field, "Road Ecology: Science and Solutions" (Island Press, 2003).
One of the first projects in this country to ameliorate the effect of roads was on Florida's Alligator Alley on Interstate 75. A series of 24 underpasses restored water flow to the Everglades and allowed wildlife to migrate safely. The changes reduced the mortality of Florida panthers — of which there were only around 50 — from four per year to 1.5.
Now, the number of ecologically sensitive road designs built or under way in the country is in the hundreds. In Amherst, Mass., salamanders emerge from hibernation in the mud on the first rainy night of April. "They come up and go screaming across the street to their breeding pond and have an orgy," Forman said.
So many were being killed that locals stopped traffic on the night they emerged to let them cross safely. In 1987, engineers placed a tunnel under the road, with two fences to funnel the reptiles to the crossing.
The gold standard for wildlife-friendly roads is in Banff National Park in the mountains of Alberta. Canada's major highway, Trans-Canada 1, passes through the park, and with 25,000 vehicles per day, wildlife-vehicle collisions were frequent.
There are 24 crossings (all but two underpasses), and they have reduced collisions with ungulates by 96 percent and all large mammals by 80 percent.
21 species particularly at risk
In the past few years the concept has become an integral part of roads, helped by a 2005 federal transportation bill that mandated green-road design. "You name it, there's something being done, even with insects," said Patricia Cramer, a research biologist at Utah State University who surveyed hundreds of domestic projects.
Such mitigation is especially critical for 21 protected species for which highway mortality is a major factor in survival, including the lynx and the desert tortoise.
The importance of preventing or undoing fragmentation has led to a swarm of environmental groups taking on connectivity — preserving the ability of wildlife to move — as an issue. Soule, for example, is a founder of the Wildlands Project, an effort to protect corridors on large landscapes.
One reason the issue has received attention is that it involves human safety. One million to 2 million wildlife-vehicle collisions occur each year, costing insurance companies more than $1 billion. Some 200 people are killed.
The increasing impermeability of roads comes as the climate changes and the need to cross roads become more crucial.
Vegetation communities here are projected to migrate north, which means grizzlies will need to be able to follow. "Shrub fields where berries are is a good example," Servheen said. "If dry weather wipes them out, the bears need to go elsewhere."
The problem is they might not be able to follow. "We've boxed them in" with roads, he said.
Roads attract wildlife, too
Roads have ecological impacts besides fragmenting habitat. Warm asphalt and rain that washes to the shoulder nourish roadside grass, and along with salt used to de-ice roads, the grass attracts deer and other wildlife. As deer get clobbered, they in turn attract predators and scavengers, such as bald eagles, which then get hit by cars.
But the downside of mitigating road impact, said Trisha White, the director of the Habitat and Highways Campaign for Defenders of Wildlife, is thinking that it heals all wounds. "The biggest danger is thinking that we can put in new roads with crossings and things will be just fine," she said. "There are so many more impacts. Nothing could be more incorrect."
Still, crossings do help. Servheen has set up heat- and motion-sensitive cameras under two highway bridges here where bears could cross under I-90, but they have not captured grizzlies using these crossings. But, he is hoping that somehow bears will move south.
"Another population will make the species more resilient to change," he said. "Whether it's a reduction in genetics or climate change, it will help with survival."
Copyright © 2008 The Seattle Times Company
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