We Need Better Highways—for Wildlife, UMD-led Research Suggests
Black Bear Study Finds Not All Wildlife Corridor Designs Are Equal
A UMD researcher and colleagues studied how to design corridors of undeveloped land to allow wildlife to flourish while avoiding conflict with humans.
Photo by iStock
A black bear padding through a suburban backyard. A hesitant deer family trying to cross a busy highway. Your dog straining at the leash in a growling showdown with a coyote on an evening walk.
Such encounters underline a growing need to set aside corridors of undeveloped land where wildlife can travel safely, helping to ensure their long-term survival as human population and development continue to expand. But a new University of Maryland-led study in the journal Landscape Ecology reveals that current methods of designing and evaluating wildlife corridors may be lacking, and that smarter frameworks are needed to ensure wildlife protection.
University researchers tested different wildlife corridor designs against black bear movement data in Florida and found that each achieved very different results, and none contained all black bear movements.
The work highlights the complexity of the issue and shows that, while there is no one best method, the purpose of a corridor, which can vary widely, will directly impact what approaches should be considered to achieve conservation goals.
“If we don’t get these corridors right, our efforts at conservation will be wasted, and we could see more human-wildlife conflicts,” said Jennifer Mullinax, an associate professor in UMD’s Department of Environmental Science and Technology and senior author of the study.
A black bear cub is tagged in Pennsylvania for a UMD study. (Photo by Gabe Mullinax)
While Florida’s black bears are no longer threatened, keeping this rebounding population and people apart requires better corridor planning methods, she said; in the case of threatened species, effective design could help bolster their very survival.
Creating corridors often requires government agencies, municipalities or nonprofits to purchase and protect expensive tracts of land or to work with developers to conserve areas that might otherwise be developed. The tracts chosen for conservation are often determined by scientific modeling based on animal movements and landscape features.
Corridors have to serve multiple species and a range of goals: One corridor may need to provide access to new habitats for an expanding population, and another may aim to improve genetic diversity by connecting populations that are separated by development.
In addition, the expense of conserving wildlife corridors isn’t backed up by solid understanding of how different design methods influence effectiveness, or even how to evaluate if they are working for the intended purpose.
Mullinax and her team used three different mathematical models to lay out as many theoretical wildlife corridors for black bears in Florida and compared them to tracking data to determine how black bears actually move through the environment. They also compared their model corridors to the existing Florida Wildlife Corridor, a network of public and private conservation lands designated as a multi-species thoroughfare across the state.
To develop potential corridors, the team combined information on bear habitats and where they are likely to live, with landscape features and information on “resistance,” or the ease or difficulty for bears to move through the environment. The study also revealed how tricky it can be to define “easy movement” to develop corridor parameters. For example, traveling across open farm fields and roadways may be physically easier for a bear than traveling through dense woods, but that’s not where wildlife officials want bears to go. And while an urban area might be more difficult for a bear to traverse than along a wooded stream, some bears will waltz right through town to find the local trash dump that they consider more of a buffet lunch spot.
The team used a program called Circuitscape to combine its resistance grids with bear habitat information and developed maps showing the most likely flow of bear movement in Florida. It’s a sort of road map that shows multiple bear “roads” and “highways” with more or less likely bear traffic.
The researchers overlayed the potential corridors with GPS tracking data on the real movements of 30 bears, each of which had been intensively tracked for an extended period. The effectiveness of corridors depended on bear behaviors; for example, the corridor that scored the lowest in most evaluations included the movements of a single unique bear apparently looking for a new home.
Additionally, what works for some animals may not work for all, the researcher found. The Florida Wildlife Corridor included fewer bears per square kilometer than the bear-specific model corridors the team designed.
The study is an urgent call for more research and resources to ensure the expense and effort of building wildlife corridors do not go to waste amid shrinking wildlife habitats and a changing climate, Mullinax said.
The study included co-authors from the Nature Conservancy, the Florida Fish and Wildlife Conservation Commission, the University of Kentucky and the Archbold Biological Station.
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