Cat in a Quandary
When biologists in Maine discovered that lynx prefer recovering clear-cuts to old growth, forest management for other species in the state got a whole lot more complicated
Roger Di Silvestro
ABOUT 100 MILES NORTH of Bangor, Maine, lies 32-mile-long Moosehead Lake, surrounded by rolling, wooded country. A few miles above the tiny town of Greenville, a pinpoint at the southern tip of the lake, the paved highway that brings visitors from the south fades into a gravel logging road, and clear-cuts sprawl on all sides--vast swaths of sun-drenched meadows erupting with the renewed growth of young trees. These regenerating stands are key habitat for threatened Canada lynx.
Maine presently harbors the largest U.S. lynx population east of the Mississippi. According to Mark McCollough, a biologist in the Old Town office of the U.S. Fish and Wildlife Service (FWS), "There are probably more lynx in Maine than ever before in state history." Based on available habitat suitable for the cat, he estimates that as many as 500 may now live in the state. If management of Maine's 17 million acres of commercial timber land is conducted in ways beneficial to lynx, the state's population could soon qualify for delisting, McCollough says. However, the type of land management needed to support the lynx may clash with the needs of other forest species. In addition, the kind of management that local forest enthusiasts are likely to endorse and the kind that helps lynx may be two widely divergent things.
FWS in 2000 listed the lynx as threatened in 13 states. Although commonly called the Canada lynx, this cat occurred historically in the Great Lakes states, the Rocky Mountains and, in the Northeast, from Pennsylvania to Maine. It was pushed out of most of the Northeast by habitat loss due to human intrusion, aided by climate change (see "Global Warming: How Temperature Affects the Lynx," below). The cat is most common in the forested northwestern parts of Maine, which today mark the southern limit of its range in the East, although individual, transient cats do appear south of Maine.
The lynx tips the scales at up to 30 pounds, with long ear tufts, a bobbed tail and massive feet that look like big, fluffy bedroom slippers and allow the cat to run with considerable ease over snow in pursuit of prey, giving it a distinct advantage over competing predators such as bobcats, coyotes and fishers.
Traditional wisdom suggests that lynx are denizens of mature northern forests, but recent studies show that lynx in Maine prefer "larger, regenerating, conifer clear-cuts" with mean annual snowfall in excess of 100 inches, says Bill Krohn, a U.S. Geological Survey biologist with the Maine Cooperative Fish and Wildlife Research Unit in Orono who has been studying the cat since 1998.
In fact, Maine's snowy, regrowing clear-cuts do not themselves attract lynx. The real attraction is the cat's key prey species, the snowshoe hare, which lives in these areas. "The story of the lynx is really a story about snowshoe hares and how clear-cuts affect hares," says Dan Harrison, a University of Maine biologist who has been researching the two animals for more than a decade. Lynx are snowshoe hare specialists. They prey on red squirrels and grouse, but in some studies 97 percent of lynx scats contain hare remains. In Maine, snowshoe hares reach highest density in conifer stands regrowing from clear-cuts, which may mimic natural disturbances such as insect outbreaks or fires.
Right after a forest is clear-cut, hare numbers drop to zero, Krohn says, but after about 15 years, conifers have begun growing back, and hares have started to return. A 20- to 30-year-old clear-cut will harbor two hares per hectare (2.47 acres). "In mature forest, you'd have only 0.2 hares per hectare," Krohn says.
Northern Maine has been especially good for lynx since the forestry industry clear-cut large areas there within the past 30 years in response to an infestation of spruce budworm. The clear-cuts have given snowshoe hares and lynx about six and a half million acres of suitable habitat--an area roughly the size of Massachusetts. (This rapid regeneration and its effects on lynx and hares may not hold true in the more arid West. In Maine, with plentiful rain and snow, new growth "comes up like dog hair," Krohn says.)
However beneficial recovering forest may be for Maine's lynx and snowshoe hares, many of the state's human residents loathe large clear-cuts. "With all the clear-cutting that occurred in the seventies and eighties, the public really reacted negatively to it," Krohn says. In response to public chagrin at forests cut to the ground across thousands of acres, the state legislature enacted the Forest Practices Act of 1989, limiting clear-cuts to 250 acres. This law revolutionized logging in Maine. The year it was passed, timber companies clear-cut about 150,000 acres, some 45 percent of land logged that year. Partial harvest, in which trees are removed selectively, accounted for 55 percent of cuts. Ten years later, clear-cuts were only 3 percent and partial harvest was 96 percent.
This trend does not bode well for snowshoe hares and lynx. Twelve years after a partial harvest, a forest supports only 0.5 hares per hectare--a fourth of what a regenerating clear-cut the same age would support. After studying the new cut pattern, Harrison, Krohn, McCollough and their colleagues reported in the journal Wildlife Biology that recent trends in favor of partial harvest "could have significant negative consequences on densities of snowshoe hare, and could affect an entire suite of carnivores that depend on hare, including the Canada lynx."
Another factor threatening the lynx is a recent, fundamental change in Maine forestry practices. Ninety-nine percent of the state's forest is privately owned and managed, and the nature of that private ownership has been changing. Seven million acres of Maine forest have changed hands since 1999, says Cathy Johnson, senior staff attorney for the Natural Resources Council of Maine, an NWF affiliate working for forest protection. Previous owners were primarily paper companies that owned their own mills for turning trees into pulp and profited from these mills. But in the 1980s, a strong market for vacation homes began to develop in the Northeast. In 1988, the Diamond International Corporation sold 970,000 acres of Maine timberland for subdivision. Other companies also started selling land to businesses that did not own mills and that had to profit from the land and trees themselves.
An example of where this shift has led can be found right at Moosehead Lake, which lies, Johnson says, in "the largest block of undeveloped forest east of the Mississippi, some 10 million acres of forest," a stretch of land roughly five times the size of Yellowstone National Park. In the past, most of it was owned by industrial forest companies, but in 1998 South African Pulp and Paper sold some 905,000 acres of Maine forest to Plum Creek Timber Company, in actuality a real estate investment trust. The largest private landowner in the United States, Plum Creek owns more than 8 million acres of timber in 18 states. Interested mainly in land development, Plum Creek wants to turn 20,000 acres it owns around Moosehead Lake into a spread of 2,300 vacation-home units, the largest development ever proposed for unincorporated townships in Maine. So far, public outcry over the plan--which would jeopardize "high-value lynx habitat and areas important for remote recreation," Johnson says--has slowed the company's acquisition of state building permits.
Plum Creek and other new landowners are changing the dynamic of forest management in Maine. Where the paper companies wanted to maintain forests during decades of ownership, the new companies plan to stay for only a few years and make quick profits. "This is the beginning of a huge change in Maine," Johnson says. "There's just no stability at all in land ownership."
The lynx is not the only animal at stake. Maine forests also harbor American martens and fishers. Martens, which feed on snowshoe hares as well as squirrels, are arboreal weasels that live in large blocks of mature forest with a canopy of connected trees. They use the canopy to escape fishers, a bulkier member of the weasel family that is the marten's primary predator. If the closed canopy is lost to logging, martens disappear, which means that the clear-cuts that help lynx are deadly to martens. Striking a balance is critical: Biologists have found that if forests are managed to protect both lynx and American martens, 82 percent of other forest vertebrates, from moose to grouse to white-throated sparrows, will also benefit, Harrison says.
To get landowners on board with logging regimens that favor wildlife, McCollough turns to such incentive-based programs as the Healthy Forest Reserve Program of the U.S. Natural Resource Conservation Service and to FWS's own Private Stewardship Grant and Landowner Incentive Program, both of which provide funds to private landowners for wildlife habitat protection. Five landowners, including The Nature Conservancy and the Passamaquody Tribe, have signed onto such incentive programs. "We hope it'll be a model for other forest owners," McCollough says. "They can still make money and yet meet these public needs for a sustainable and viable forest."
McCollough remains cautiously optimistic about the lynx. "This species' recovery should be a win-win for forest industry," he says. The result will be a viable lynx population 20 years from now. "But we need the help of the Maine forest industry to accomplish that," he says.
Senior Editor Roger Di Silvestro visited scientists in Maine while researching this story.
Global Warming: How Temperature Affects the Lynx
One of the most critical threats facing lynx is global warming, says U.S. Fish and Wildlife Service lynx biologist Mark McCollough. As climate warms, diminished snowfall likely will allow predators such as coyotes to compete more effectively against the lynx, which already faces tough challenges: In Canada, 70 to 80 percent of lynx do not make it past three years old. Global warming also is likely to affect rainfall, critical to maintaining forest habitat.
The Cat Connection: Bobcats, Lynx and the Process of Exclusion
Snow depth and the availability of snowshoe hares are not the only factors limiting lynx distribution. Another important element is the presence of bobcats.
Bobcats closely resemble lynx, though they tend to be shorter legged and more reddish than gray. Most importantly, they lack the huge feet of the lynx, which means that they cannot move efficiently over snow. But bobcats, much more aggressive than lynx, tend to drive their big-footed relatives away from habitat where the two meet.
Bobcats and lynx do not overlap in most of their range (see map). Why they do not is clearly demonstrated in Maine. In the early 1900s, when wolves were wiped out in the state, bobcats moved in, fed on the large deer population and pushed lynx northward. In the 1930s and 1940s, says biologist Bill Krohn, bobcat numbers burgeoned in northern Maine. But during the spruce budworm outbreak in the 1980s, when trees died off and large areas were clear-cut, deer numbers dropped. In areas with deep snow, bobcats could not find sufficient food in winter and could not compete against lynx for snowshoe hares. Bobcat range ebbed southward, and the lynx again took over much of northern Maine.
A similar balance between lynx, bobcats, snowshoe hares, deep snow and big feet may prevail throughout the cats' ranges, creating a subtle ecological dynamic across the continent.
NWF in Action: Helping New England Wildlife
NWF's Northeastern Natural Resource Center in Montpelier, Vermont, is working for better protection of a variety of New England predators. Staff also have been training volunteers for follow-up on reports of wolf sightings in the Northeast, which helps the U.S. Fish and Wildlife Service (FWS) determine whether the area is home to breeding wolves. NWF played a key role in peregrine recovery in Vermont, where the group has continued to help the falcon by funding and working on post-delisting monitoring activities required under the Endangered Species Act. To learn more visit www.nwf.org. NWF's state affiliate, the Natural Resources Council of Maine, has been working to ensure that real estate development plans on forest lands take into account the habitat needs of Maine wildlife. See www.nrcm.org.
The Lynx's Maine Domain
In the Northeast, the lynx was once common historically from Pennsylvania to Maine, but it was pushed out of most of that region by habitat loss due to human intrusion, aided and abetted by climate change.
From around the year 1500 into the 1800s, a regional climate fluctuation called the Little Ice Age drove down temperatures throughout the Northeast and brought increased snowfall. The bitter winter that George Washington spent buried in snow at Valley Forge was typical of that era. Today, such winters rarely occur south of Montreal, Quebec, says Bill Krohn, a U.S. Geological Survey biologist.
That weather was perfect for lynx, and the end of the Little Ice Age, along with habitat loss, drove the lynx northward. Today, the cat is limited in the Northeast to parts of Maine.
Evidence suggests that lynx have reproduced in Maine for at least the past 200 years, but in 2000, the year the lynx was federally listed as threatened in 13 states, the Maine wildlife department did not believe the state harbored a breeding population. Conventional wisdom suggested that lynx found in Maine were transients from Canada. The Maine Department of Inland Fisheries and Wildlife began radio-telemetry work on lynx, collaring animals with transmitters that could be used to locate the cats. The study established that a breeding population of lynx inhabited Maine, particularly previously cut, recovering Northern Forest with deep winter snow--the type of habitat that attracts snowshoe hares, the primary food of lynx.--Roger Di Silvestro