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On the LookoutAcross the Northeast, indicator species offer clues to ecosystem health By Katharine Wroth AMC Outdoors, March/April 2011 About this time each spring, a curious parade occurs in the forests of the Northeast. Emerging from the rocks and rotting logs that sheltered their frozen forms all winter, wood frogs make their way to nearby wetlands to breed. Specifically, they seek out vernal pools, those shallow, water-filled depressions that provide standing water for only a few months, disappearing nearly as quickly as the darling buds of May.
Wood frogs and other species, including spotted salamanders, depend on vernal pools—known more formally as "ephemeral wetlands" and colloquially as "wicked big puddles"—as a breeding ground because they're generally free of predators. But these areas and their denizens are increasingly threatened, by development, pollution, deforestation, and even the specter of climate change. Scientists keep a careful eye on wood frogs and other vernal pool frequenters to understand the health of the wetland ecosystems. The frogs are considered an indicator species—a sort of canary in the coal mine that can let observers know if something has gone wrong. If the frogs stop showing up, or their jelly-like egg masses change or fail, the message is clear: This mini-ecosystem and its surroundings may be suffering. Vernal pools aren't the only place where a single species can offer a host of clues to what's happening around it. In fact, throughout the Northeast, scientists and land managers rely on such species to offer evidence—through their behavior, their health, or their very presence or absence—about the status of the region's mountains, forests, wetlands, and waterways. While techniques such as mapping and sampling can provide information about habitat fragmentation or changes in water quality, looking closely at a species can show how the impacts of these changes are felt over time. For AMC, this type of monitoring comes in handy from the peaks of the White Mountains to the forests of Maine, and from the depths of a dam relicensing decision to the bluster of a windpower siting debate. "We look to indicator species to determine whether an ecosystem is healthy, showing signs of stress, or highly degraded," says AMC Research Director Ken Kimball. "It's similar to using the unemployment rate as an indicator of a healthy economy; it's not the whole answer, but it's a very good clue." With threats such as development, pollution, and climate change putting ever-greater pressure on ecosystem health, this biological warning system is increasingly important. While the wood frogs get busy, here's a look at a few other species of interest in the Northeast.
Brook trout—or "brookies" as they're known to their fans—are a beloved fish in these parts, and one of the species most at risk when waterways become compromised by dams, logging, pollution, or other factors. "Brook trout are a major focus in the Northeast," says Kimball, noting that their presence in AMC's Maine Woods Initiative waterways means the waters are cool and clean, uncompromised by silt and warming temperatures. Because of their specific habitat requirements, brookies are also a key piece of the dam-relicensing puzzle; if they're happily hanging out and reproducing below a dam, it's a good indication that the facility is operating in relative harmony with its surroundings.
Take a hike in the White Mountains this spring or summer, and you might see a fellow hiker hunched over some of the tiny flowers scattered across those rock-strewn slopes. Each year, thousands of volunteers collect data on when alpine flowers bloom in the White Mountains as part of AMC's Mountain Watch program. This program studies alpine flowers such as diapensia because they are the most at risk from climate change: Rare species with restricted ranges, they have literally nowhere to go if their mountaintop homes become inhospitable. By keeping track of when diapensia and other plants bloom and how long they flower, says Kimball, “we can determine the long-term viability of arctic species in alpine areas. We are picking apart the species' life cycle to see if it is beginning to exhibit biological shifts."
This petite songbird, described as an "extreme habitat specialist" by the Center for Biological Diversity (CBD), makes its home in high-elevation spruce-fir forests that have been disturbed by storm damage, insect outbreaks, or other factors. The bird's preferred accommodations aren't exactly a dime a dozen to begin with, and subalpine zones are increasingly threatened in the short term by development (they're a popular site for wind-power projects, ski areas, and communications infrastructure) and in the long term by climate change. So researchers keep an eye on thrush populations to find out just how these areas are evolving—and also use them as evidence that an area should not be developed. "You know an area is ecologically significant for multiple species if the Bicknell's thrush is present," says AMC Senior Staff Scientist Dave Publicover. In fact, the species is so crucial to scientific understanding that the CBD petitioned the federal government in late 2010 to list it under the Endangered Species Act.
Once upon a time, says Publicover, forest management amounted to a philosophy akin to, "As long as the trees grow back, everything else will take care of itself." We've come a long way since then, of course, and at AMC's Katahdin Iron Works property and other forests in Maine (as well as other northern reaches of the country), land managers look to these small mammals, cousins of the weasel, as a clue that things are on track. "If you maintain suitable habitat for the marten, you'll provide habitat for a wide range of other species that use mature forest," says Publicover. Indeed, a report from Maine Audubon suggests that by managing with the success of the marten in mind, land managers will also create a healthy habitat for three species of reptile, eight species of amphibian, 40 species of mammal, 80 bird species, and hundreds, if not thousands, of plant, fungi, and insect species.
There's nothing showy about freshwater mussels, which spend most of their time burrowing in the muck on the bottom of our region's rivers. But these bivalves have a starring role when it comes to ecosystem health: "Freshwater mussels are telling us a story about water quality," says Julie Victoria, a wildlife biologist with the Connecticut Department of Environmental Protection. Since 1990, the agency has carefully studied the 12 species of freshwater mussel that call the state home, producing a field guide and encouraging citizens to report sightings of shells and live specimens (see sidebar). These "living filters," as Victoria calls them, help keep water clean; they are also particularly sensitive to pollutants. A decrease in the number of mussels can be an early sign that something's gone wrong. As the New Hampshire Department of Environmental Services puts it, "Mussels can indicate a water quality issue long before even the most sophisticated scientific equipment can detect a problem."
Each summer, swimmers and boaters in Chesapeake Bay face an especially unpleasant foe: the sea nettle, a type of stinging jellyfish. While "jellies," as they're known, aren't a classic indicator species, they have long been a species of interest in the Bay—and are gaining increasing attention around the world as researchers study the connections between their booming populations and warming waters attributed in part to climate change. Yale University researcher Mary Beth Decker has spent more than a decade studying sea nettles in the Bay, and says that fluctuations in temperature, stream flow, and salinity have a direct effect on jelly populations in a given year. Nutrient-rich waters that are a result of agricultural runoff may also encourage jellyfish to bloom. But Decker hesitates to make jellies the ultimate storyteller: "People want to say that jellyfish are an indicator of a degrading ocean, but there isn’t consensus yet. It's a complex issue, with lots of factors at play." One thing is certain: Like other plants and animals in the Northeast, jellyfish offer clues about the impact of humans on our region's ecosystems. By watching carefully, scientists may be able to spot trouble before it's too late. |
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Scientists keep a careful eye on wood frogs and other vernal pool frequenters to understand the health of the wetland ecosystems.
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Brook trout (Salvelinus fontinalis)
Diapensia (Diapensia lapponica) and other alpine flowers
Bicknell's thrush (Catharus bicknelli)
American marten (Martes americana)
Yellow lampmussel (Lampsilis cariosa) and other freshwater mussels
Sea nettles (Chrysaora quinquecirrha)
