Food-chain reaction: Vt. wildlife shifting with weather
Vyto Starinskas / Staff Photo
The bald eagle, such as this one seen over Lake Bomoseen in Castleton last winter, are among the bird species gaining ground due to conservation efforts and climate change.
Editor’s note: Five years ago, this paper explored recent climate shifts in a set of reports titled “Vermont’s Changing Seasons.” This story is part of a monthly series of updates.
By Kevin O’Connor
As a biologist for the Vermont Fish and Wildlife Department, John Austin helps keep score of the state’s 40 species of reptiles and amphibians, 58 species of mammals, 91 species of fish, 258 species of birds and more than 20,000 species of invertebrates.
Lately, warmer weather has thrown him a curveball.
Longer summers and shorter winters are extending Vermont’s growing season and variety of habitats and harvests. That’s good if you’re a black vulture or other animal lured by the forests and fruits that sprout with more moderate temperatures. But that’s bad if you’re a Bicknell’s thrush or other cold-environment creature that’s increasingly finding the state too hot to handle.
“Climate change is having and will continue to have significant effects on Vermont’s fish and wildlife,” Austin has written in a recent state report. “Certain species may simply disappear. At the same time, other species of plants and animals may thrive.”
In this only-too-real game of Survivor, “there will be winners and losers,” Austin says. He’s speaking not only about wildlife but also of the 62 percent of Vermonters who fish, hunt or watch birds — netting the state related spending of more than $700 million.
Vermont boasts one of the highest numbers of breeding bird species in the continental United States. But while some populations are increasing, others are decreasing, according to the Vermont Breeding Bird Atlas, first published in 1985 and set for a second edition next year.
Statewide counts are finding some species gaining because of conservation efforts — specifically, the bald eagle, common loon, osprey, peregrine falcon and wild turkey. But other birds — Southern species such as cardinals and Carolina wrens, for example — are flying north simply because it’s feeling more like home.
Red-bellied woodpeckers once were so rare in the Green Mountains, they weren’t recorded in the first atlas. A quarter-century later, they’re common enough that the second edition will report sightings in seven of Vermont’s 14 counties, including northernmost Grand Isle.
On the flip side, rising temperatures are threatening to reduce the breeding range of several species that prefer cooler climates.
Consider the Bicknell’s thrush, a relatively rare songbird that inhabits the spruce and balsam firs atop mountain peaks. In Vermont, nests can be found on such summits as Mansfield (the state’s tallest at 4,393 feet) and ski slopes including Killington and Stratton. But warmer weather is supplanting the traditional conifer habitat with more Southern trees, studies show.
As a result, the Bicknell’s thrush is one of 57 birds on the Fish and Wildlife Department’s “Species of Greatest Conservation Need” list, while the U.S. Fish and Wildlife Service is considering placing the bird under the protection of the federal Endangered Species Act.
Biologists and birdwatchers say everyone should care about the Bicknell’s thrush because the state’s ecology is woven together like one big nest. Such birds don’t simply sing and fly, they also pollinate plants, disperse seeds and eat insects such as the gypsy moths, tent caterpillars and eastern spruce budworms that can threaten orchards and woodlots.
Down in the valleys, Vermont’s rivers and streams offer some of the best wild brook trout conditions in the East. But as the state’s average temperatures are increasing, cold-water fish habitat is decreasing.
Brook trout — the state’s most widely distributed and only native stream-dwelling trout — require the high levels of oxygen found only in clear currents of 50 to 65 degrees. But fluctuating weather — running the spectrum from flash flooding to drought — has led to fluctuating levels of water and aquatic life.
Many fish spawn in the spring in response to snow melting into rivers. Not enough water can endanger the start of the cycle, while a freak storm can wash out all the nests where eggs are laid. A summer drought, for its part, can diminish a stream and decrease fish size. And if fall spawning comes with low stream levels, rivers can freeze to the bottom in the winter, killing the eggs that require a flow of oxygenated water.
While nearly 14 percent of Vermont’s watershed is deemed healthy for brook trout, another 63 percent has degraded because of warmer temperatures and other changing conditions, according to a first-ever study by the Eastern Brook Trout Joint Venture, made up of 17 state fish and wildlife agencies, five federal environmental offices and several conservation groups and schools.
Another 5-degree rise in average temperature, the U.S. Environmental Protection Agency warns, could eliminate brook trout entirely in Vermont.
As cold-water fish wane, warm-water varieties are moving in. Bass are a native species west of the Green Mountains but not to the east. Yet because they don’t need as much oxygen and thus thrive with rising temperatures, they’re multiplying throughout the state.
Trading bass for brook trout comes with consequences.
“People value brook trout not only for their beauty, their delicious taste, and their sportfish qualities, but also as indicators of the broader health of the watersheds where they live,” the Eastern Brook Trout Joint Venture says on its website. “Strong wild brook trout populations demonstrate that a stream or river ecosystem is healthy and that water quality is excellent. A decline in brook trout populations can serve as an early warning that the health of an entire system is at risk.”
In the end
Climate change promises to ripple throughout Vermont’s food chain.
“As species relocate on the landscape and change the timing of important natural processes (e.g. reproduction, migration),” Austin writes in his report, “it is possible that some natural community associations, predator-prey relationships or species habitat preferences will be entirely unlike present-day interactions and may lead to unanticipated consequences.”
Warmer weather, for example, promises to increase populations of deer and opossum, the report says. But it could decimate weasel-like martens, an endangered species in Vermont that lives in the diminishing spruce and fir forests of the Northeast Kingdom. And it could diminish moose, which are facing an increase in heat-loving, disease-laden ticks.
Austin and his colleagues understand they can’t single-handedly stop global warming. But the state is aiming to better address the shifting situation.
“The future of fish and wildlife is unpredictable because we know things will change — we just don’t know how or when,” the biologist says. “We have to think more carefully about how we’re going to track and monitor those changes. And, even more important, we need to be strategic about how we respond so we can successfully conserve our native plants and animals.”
The state also is working to maintain enough varied habitats “so that species have an opportunity to move and adapt in response to whatever changes may occur,” Austin adds.
The Fish and Wildlife Department, for example, is collaborating with the Vermont Agency of Transportation, governments in surrounding states and nonprofit conservation organizations on a “Staying Connected Initiative” to identify and protect travel corridors for animals. It’s also seeking to educate the citizenry, whose property makes up 80 percent of the state.
“Private landowners continue to hold the key for wildlife conservation in Vermont,” Austin says. “Fish and wildlife will respond to climate change in various ways, but their ability to respond is only as good as their ability to move within the broader landscape. In the end, it’s all about conserving habitat.”