New tool helps assess climate stress on vulnerable wildlife

March 1 2014 |

When wild species join the gloomy elite—the list of threatened, vulnerable, endangered or extinct-in-the-wild—wildlife managers work aggressively to save them and their habitats. A new analytical tool that measures the potential impact of climate change on ecosystems could make these efforts more strategic and cost-effective.

Ben Zuckerberg
Benjamin Zuckerberg, Assistant professor of forest and wildlife ecology at UW-Madison.

In most cases, plant or animal species are struggling because their native ranges have been lost to development. Researchers are now realizing that climate change is another risk factor that can thwart even the best protection efforts. So, the crucial task of picking the best management strategy to help a species in a given area is turning out to be quite the challenge.

“Typically we think of land-use changes determining the fate of a given species,” explains Benjamin Zuckerberg, an assistant professor of forest and wildlife ecology at UW-Madison. “But now, using climate data, we can predict which populations will actually blink off.”

Zuckerberg, a member of the Wisconsin Initiative on Climate Change Impacts (WICCI) Wildlife Working Group, is developing quantitative methods for pinpointing factors that hasten species’ success or decline. To enumerate climate change impacts on wildlife, Zuckerberg makes use of big data sets, including WICCI climate data and information provided by non-professional observers, or “citizen scientists.”

“Climate is very different from weather; it’s 30 years versus one year,” says Zuckerberg. “Rather than trying to study a few species on a few hectares of land over a few years, climate change work requires broad study over time and geographic space.”

Every species is tied to its own ecosystem, with select factors contributing to survival, though one is often essential. For example, the eastern massasauga rattlesnake, one of the species Zuckerberg is studying, is closely tied to local water tables. These Wisconsin pit vipers live in low-lying bogs and fens. In winter, they hibernate below ground in crayfish burrows, regulating body temperature and hydration by shifting in and out of the unfrozen groundwater.

These are shy creatures that give birth to live young. As recently as four decades ago, these snakes were considered pests, with bounties paid for rattler tails. Today, Wisconsin’s few remaining massasauga populations are listed as endangered and protected by state law, having lost much of their habitat to suburban and agricultural development. Zuckerberg’s research now shows that climate change is hastening the snake’s decline.

With support from the Upper Midwest and Great Lakes Landscape Conservation Cooperative, Zuckerberg and post-doctoral researcher Lars Pomara dug into WICCI climate data to determine what aspects of Wisconsin’s changing climate are working against the massasaugas.

eastern massasauga rattlesnake
The eastern massasauga rattlesnake, a Wisconsin pit viper, depends on groundwater levels for hibernation.

Pomara developed statistical models to characterize how survival rates relate to climate history and habitat changes for snake populations. These relationships were then used to develop computer simulations that mimic and predict massasauga population changes, resulting in a modeling tool that can spell out the relationships between decades of environmental change and fluctuations in rattlesnake numbers.

“We ran these climate vulnerability assessment models at all population locations, using the history of climate and land cover dynamics of those places, to see what would happen to those populations,” says Pomara. “Then we compared the results to actual population status, which was based on field information.”

By setting population and habitat factors against a backdrop of historical weather data and WICCI climate projections, Pomara and Zuckerberg found climate change to be a major player in the snake’s chances of survival, escalating stress on the animal through more summer floods and winter droughts.

“Applying this climate vulnerability assessment method to other species will help wildlife researchers identify non-harvested species that are vulnerable to climate change, and if they become listed, then there are the hard choices of habitat conservation and the struggle that comes with this,” says Zuckerberg.

Wisconsin is already experiencing shifts, with some southern species expanding northward. For example, wild turkeys and cardinals are moving into northern Wisconsin forests, and snowshoe hares -- denizens of the Wisconsin prairie-forest boundary and whose fur turns from brown to white based on hours of daylight -- are becoming easy marks to predators when the snow does not come and go as it once did. These examples offer a hint at the kinds of challenges wildlife managers may face in the future.

“Forest managers anticipate that pines, spruce and paper birch will be replaced by oaks, maples and other tree species adapted to warmer conditions over the next 100 years,” says Michael Meyer, a wildlife research scientist with the Wisconsin Department of Natural Resources and a WICCI affiliate. “Harvest management of many wildlife game species may need to be adjusted, and habitat management within state wildlife areas and forests may need to be altered to meet the conservation needs of species identified as ‘at risk’ by climate vulnerability assessment modeling.”

“Massasaugas really are a beautiful, rare and unique piece of the upper Midwest’s natural heritage—part of what makes Wisconsin what it is,” says Pomara.

The snakes are already rare in Wisconsin, with only five or six remaining small populations. But now, at least, wildlife managers have an additional tool to determine which populations stand the best chance of survival.