Pathways to Climate Safety

Connectivity of habitat corridors

american-black-bear
Even though the three species occupy similar habitats, changing climate and land use will affect corridors between habitats very differently. Photo by Tim Lumley, Flickr.

When forest animals need to leave their home territories, because of climate change impacts like drought, flooding, or heat or because humans are moving in, where do they go?

They need a habitat corridor or pathway – with tree cover, food, and water – to protect them on their journey to a nearby suitable habitat.

USDA Forest Service scientist Jennifer Costanza and colleagues studied pathways available to three species in need of conservation in the southeastern U.S.: the timber rattlesnake (Crotalus horridus), American black bear (Ursus americanus), and Rafinesque’s big-eared bat (Corynorhinus rafinesquii). Their results were published in Biological Conservation.

The different animals face different challenges. Even though they currently live in similar habitats, changes in climate and land development will affect their existing corridors differently.

The scientists modeled and mapped each species’ pathways. The maps were overlaid on maps of potential changes in temperature, precipitation, and land use.

Most pathways for the bat face a big threat from climate change. Almost half of the bat’s important linking paths also have a high probability of land use change and little protection — meaning the species may need human help to survive.

If their corridors aren’t protected, the bats may need scientists and land managers to transport them to safer ground or breed them in captivity and release them in the wild.

Like the bat’s, most of the bear’s important linkages have high levels of threat from climate change and a low degree of protection. The authors recommend that conservationists consider protecting alternative corridors.

Listen to a brief audio clip by author Jennifer Costanza describing this publication. • Text Transcript

The rattlesnake fared better in the study’s models. Many of its corridors in mountainous and northern regions of the Southeast are expected to be less impacted by climate change.

Linkages that may be more climate-stable than the surrounding landscape will be lifesaving harbors for wildlife at risk. They are important to preserve from human incursion, the researchers wrote.

“In a lot of cases, climate wasn’t the top threat for the connectivity we mapped,” says Costanza. “It was land use change.”

In 2019, Costanza and Adam Terando examined whether existing connectivity models included effects of habitat destruction from housing and roads as well as climate change. Most did not. Unpredictability of human land use is one reason, they suspect. Also, there are no consistent, readily available simulations.

For the recent study, Costanza used a land use change model that she and Terando created for an earlier study on urbanization. It warned that the future health of southeastern U.S. ecosystems and survival of wildlife species depend as much on urban sprawl as on climatic warming.

Urban area is expected to at least double by the middle of this century. Climate change models predict average annual temperatures are likely to increase across the Southeast 2.4°C by mid-century, in every season. Cities may add another 0.5°–1.5°C.

habitat-pathway-map
Areas in red are likely to need adaptation assistance, because climate and land use changes will be large, while habitat protection is low. USFS image.

Costanza is part of a national team mapping land use change projections as for the decadal Resources Planning Act (RPA) assessment. “There’s a lot of data coming on that horizon,” Costanza says. “More and more, that gap is being filled.”

But documenting the march of southern urbanization is not enough. “Taking action before these projected changes occur will be critical for successful conservation,” the researchers write.

Costanza cites two southeastern regional efforts: the Southeast Conservation Adaptation Strategy, working with stakeholders to identify places essential for connectivity, and Keeping Forests, funding efforts to identify appropriate management actions that maintain forest area.

Virginia state law protects wildlife corridors. Yet “the local level is where the rubber meets the road,” says Costanza.

Durham County, NC has funding to identify specific parcels that should be priorities for connectivity and conservation. “Then they can decide what should be done on those parcels, whether they should be bought by a conservation group, or the zoning should encourage low-density development, if any,” adds Costanza.

Read the article in Biological Conservation.

For more information, email Jennifer Costanza at jennifer.costanza@usda.gov.

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