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Pennsylvania: Climate Change Brings Uncertain Future for Bog Turtle

A bog turtle sits in what looks like hay and grass
The impacts of climate change could amplify other threats to the bog turtle, such as habitat loss and fragmentation. Photo: Gary Peeples, USFWS. Download.

In October 2010, the U.S. Fish and Wildlife Service established the Cherry Valley National Wildlife Refuge in northeastern Pennsylvania, in part, to protect the federally threatened bog turtle. Climate change, however, could amplify existing threats to the turtle’s fragile habitat. 

The Pennsylvania Fish and Boat Commission, Pennsylvania Natural Heritage Program, and the Pennsylvania Department of Conservation and Natural Resources all have identified habitat loss and fragmentation -- mostly due to development -- as the main threat facing bog turtles.

When the Refuge boundary was established, Cherry Valley was experiencing a surge in residential development that threatened the turtle’s habitat -- wet meadows and other shallow, sunny wetlands. In a November 2010 article in Refuge Update detailing establishment of the refuge, Refuge Manager Michael Horne said the first parcel acquired for Cherry Valley National Wildlife Refuge’s provided “promising wetlands in terms of bog turtle management.”

Horne says the refuge is working with partners, such as The Nature Conservancy, the Pocono Heritage Land Trust, and local townships to get baseline information on turtle populations so they can gauge future changes in behavior. While the effects of climate change on the bog turtle are uncertain, he says even a slight change in temperature would be enough to affect the species.

A report by the U.S. Global Change Research Program says annual average temperature in the Northeast has increased by 2°F since 1970. This warming has resulted in other changes that could affect turtle habitat, such as more frequent very hot days, a longer growing season, changes in precipitation patterns and hydrology and rising sea levels.

A juvenile bog turtle being held in human hands
A biologist examines a juvenile bog turtle as part of a field study. Photo: Rosie Walunas, USFWS. Download.

“We do have some concerns because the species is impacted by small changes in temperature, and its habitat is driven by freshwater springs,” Horne says. “The bog turtle relies on open habitat for nesting purposes and springs for clean water, as well as springs with a constant temperature for hibernation.” Any changes in climate associated with springs and nesting could potentially affect the turtle.

According to the Endangered Species Coalition, climate change could exacerbate impacts to bog turtle habitat by “altering hydrological cycles,” which would either cause the turtle’s habitat to flood or dry out. Scientists also have linked warming climate to the spread of certain invasive species in the region, such as purple loosestrife, which could decrease water levels.

Alison Whitlock, coordinator for the U.S. Fish and Wildlife Service’s Northeast Region bog turtle recovery program, says bog turtles require a specific spring-fed wetland habitat that maintains a fairly consistent water level throughout the year. The turtles nest on hummocks that sit just a few inches above the water, so if climate change results in unusually high flood events in the summer months, nests will certainly be lost. On the other hand, if climate change causes the water level to drop below the surface, then turtles would lose the shallow water and mucky substrate upon which they depend for foraging, cover and hibernation. 

A scenic view of Cherry Valley
Cherry Valley National Wildlife Refuge was established in part to protect the federally threatened bog turtle and its habitat. Photo: Friends of Cherry Valley.

Whitlock says another unknown for the northern population of bog turtles is how climate change might affect nesting, or more specifically, “degree days”—the length of time in which a certain temperature is reached to successfully incubate the turtle eggs. Colder summers in the northeast have seen failure of nests, so a longer growing season could potentially increase their nest success. 

“We won't know the effects of climate change on bog turtle habitat until we see what it brings,” Whitlock says. “In the meantime, we need to better understand the ecological relationship between the bog turtle's habitat and its hydrology, as well as concentrate on protecting these landscape features from the more immediate threats of development and invasive species.”

 

Climate Change Focus: Adaptation

Author: Joe Vickless 

Contacts: Terri Edwards, 413-253-8324, terri_edwards@fws.gov 

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