Road Map to Refuge

Tess O’Sullivan slips off her daypack and reclines against a white-barked tree. The shade of this aspen grove dissipates the August heat. It’s an ideal spot to break after a morning’s hike in the high desert sagebrush of Idaho’s Pioneer Mountains. O’Sullivan, the land conservation strategy lead for The Nature Conservancy in Idaho, sifts through her pack just as three dusky grouse flush out from a patch of brush. Overhead, chickadees flit from branch to branch. Elk droppings are scattered in moist seeps throughout the thicket.

It’s not difficult to see the appeal of aspen in the high desert, whether you’re a human on a hike or a foraging elk. But this stand of trees is more than an oasis. Scientists call it a microhabitat, and this variation in the landscape—like a steep slope, a deep snowdrift or a pool of water—may be the key to helping species adapt to climate change.

For more than a decade, Mark Anderson, TNC’s director of science for the eastern United States, has helped the organization develop an innovative and dynamic approach to conserving land so species have room to thrive. “To discover what makes one area more resilient than the next, we looked at the properties of the land itself,” says Anderson. “We need to protect nature in a way that allows species to move and change regardless of the exact climate scenarios.”

Instead of predicting how high temperatures will rise, how much precipitation will fall or how soon snowpacks will melt, a cohort of more than 150 TNC scientists led by Anderson identified a spectrum of habitats best equipped to support species through climate shifts. 

The 2.4 million acres from the peaks of the Pioneer Mountains to the lava fields of Craters of the Moon National Monument and Preserve are part of this newly mapped network of resilient lands. These safe havens—like O’Sullivan’s stomping grounds in the south central part of the state—boast a variety of microhabitats, are rich in biodiversity and allow species to freely move to adjacent strongholds.

“A map of resilient places helps us prioritize land conservation in Idaho,” says O’Sullivan. “This isn’t just about protecting land that is important to wildlife now; it’s about protecting land that is going to be important for the future.”

To identify which lands in the United States are most resilient to climate change and can support the most diverse range of plants and animals, Anderson and his team started by combing through a vast database of spatial information, some of which has been collected across TNC’s nearly 70-year history. Researchers profiled every acre of land in the lower 48 states, noting ecological features (such as landforms, elevation zones and wetlands) and cataloging land use (including the presence of development, agriculture and energy infrastructure). In the process, a handful of characteristics surfaced that scientists began to recognize as the hallmarks of resilience. 

One strong indicator is the availability of local habitats with varying topography, soil composition and elevation, which offer a range of climates for flora and fauna. In Idaho’s Pioneers, they could be isolated meadows or the canopy cover furnished by aspen groves. 

“The direction a slope faces, low wet basins, little islands of habitat—these all influence the temperature near the ground,” says Anderson. As the world warms, he says, landscapes that offer a range of physical environments and corresponding temperature gradients will allow communities of species to move around without having to move on. 

Another sign of resilience is biodiversity. For decades, TNC has focused on preserving areas with intact habitats and populations of rare species. 

In Idaho, a rocky moonscape of former lava flows transforms into sagebrush prairie before giving way to the undulating, conifer-studded foothills of the Pioneers. This varied landscape of public wildlands and private working lands supports sage grouse and redband trout, badgers and beavers, wolves and wolverines. 

Not all landscapes that have emerged as resilient are as remote as Idaho’s Pioneer Mountains. Some, like the Appalachians, which stretch from central Alabama into Canada, are bordered by densely populated cities. Others, like Nebraska’s Central Platte River, which includes TNC’s Platte River Prairies, may not have the elevation of mountainous regions, but possess topography so complex (in this case, a chain of grasslands and wetlands) that they can support a wide array of wildlife, like the 1 million or so sandhill cranes that stop over during their spring migration. 

To showcase the nationwide distribution of these resilient sites and natural corridors, Anderson’s team mapped what’s known as the Resilient and Connected Lands Network (see map on page 57). The network contains examples of all habitat types in each region, accounts for 250,000 locations of rare species and unique natural communities, covers 33% of the contiguous United States—and serves as a north star for the conservation of the country’s most climate-resilient land.