How far would you have to move in these 100-degree days to find a place 10 degrees cooler?
Humans might have to drive for days. But a bug on an arrowleaf balsamroot flower might only need to shift to a different leaf.
“If you look at the plant with a thermal infrared camera, its astonishingly diverse,” said Art Woods, an ecophysiologist at the University of Montana. “Within a single plant, you can get a 10- to 15-degree range of surface temperatures. That’s what you get across hundreds or thousands of kilometers of latitudinal change. The local diversity of a plant is really extreme.”
And animals, especially tiny ones, have learned to take advantage of that fact. Woods and his colleagues around the world have been scrambling to document how they use these microclimates to survive, and what might happen as the macroclimate governing whole continents changes around them.
“What an animal experiences is not climate as we think about it,” Woods said. “We’re used to the large-scale, measured by weather stations and computers. What individual animals experience is quite different. They live in really small spaces — on plants, or on the ground, or underground. And superimposed on that is the amazing fact that animals modify their environments by where they choose to go and the kinds of things they build.”
Take a less-than-popular example for many Montanans: The tent caterpillar. These garden pests get their name for the gauzy gray shrouds of silk they weave in the branches of ornamental trees, which hold dozens or hundreds of leaf-munching insects in their larval stage.
Tent caterpillars hatch from their eggs in early spring, when Montana temperatures are typically quite cold. The larva quickly spin silk into the often kite-sized tents, which collect warmth from the sun that protects them from the surrounding chill until they’re mature enough to transform into butterflies.
“A lot of people think of tent caterpillars as pests, but they’re amazing ecological engineers,” Woods said.
But as Montana’s climate has shifted warmer over the past decade, those tents could turn into a liability. Longer, hotter springs such as Missoula saw this year may mean instead of protection from cold nights, the tents could absorb too much solar heat and cook their occupants.
Similar problems confront a wide range of Montana fauna. The recently identified Western glacier stonefly native to Glacier National Park depends on icy-cold meltwater from mountain glaciers for part of its life cycle, and the park is rapidly losing its high-altitude icefields.
Wolverines raise their kits in thick snowbanks, digging burrows up to 20 feet deep repeatedly over the late winter and early spring as they move from their natal to their maternal dens. As natural historian and biologist Doug Chadwick recounted in “The Wolverine Way,” “you might even be justified in thinking of Gulo gulo (the wolverine’s scientific name) as the land-based equivalent of the better-known polar bear.”
Woods recently published his findings in the journal Trends in Ecology and Evolution, along with colleagues at the University of Montana, the University of Wyoming, the University of Tours in France and Stellenbosch University in South Africa. The group’s next move is to identify similar animal communities in North America, Europe and South Africa and chart their reactions to changing climates around the globe.
“Climate change is imposing a new set of conditions on biomes around the world,” Woods said. “As you study these species, they shift or disappear or fall apart all together. Time is running out for many of the things we love.”