ROBERT SIEGEL, HOST:
The Northern arm of the Rocky Mountains is sometimes called the crown of the continent. Among its jewels are glaciers and snow fields that irrigate part of North America during the spring thaw. But the region is getting warmer, even faster than the rest of the world. NPR's Christopher Joyce recently visited scientists in Montana who say warming is scrambling the complex relationship between water and wildlife. It's threatening some with extinction.
CHRISTOPHER JOYCE, BYLINE: I'm flying over northern Montana's mountains in a Cessna two-seater with ecologist Richard Hauer. Snowcapped mountains and wide valleys are spread out below. Hauer calls this place a giant sponge. Moist air from the Pacific hits the mountains and falls as snow and ice. It sits in the mountains until spring when it melts and runs through the gravel valleys and across big parts of North America. It's worked that way for millennia. But lately, Hauer says, Montana is warmer, and the spring melt starts earlier and flashes through this sponge much faster.
RICHARD HAUER: There's change that takes place because the snowmelt is occurring earlier. And, basically, if you turn the spigot on earlier, it runs out of water sooner.
JOYCE: Running out of water sooner means drier summers, just when plants and animals and people need it most. Ecologists like Hauer, who's at the University of Montana, say there are other changes as well - retreating glaciers and more flash floods. Scientists are studying how all this affects wildlife - wildlife that's important for holding together the whole ecosystem here. I joined three ecologists from the U.S. Geological Survey on a mountainside a couple of thousand feet below Hauer's flight path. We're hiking up into a snowfield in Glacier National Park, toward a stream flowing down from the snow.
JOE GIERSCH: Great place to be if you're an obscure, high alpine stream insect.
JOYCE: Obscure insects are Joe Giersch's life. Several species of rare, but important, insects live here in 40-degree meltwater. Giersch bends over the stream - it's only a few inches deep - and turns over a few rocks. In 10 minutes, he finds what he wants - a tiny, brown, wet smudge of a fly.
GIERSCH: All right. This is lednia tumana.
JOYCE: Now, come on, you can really tell the species?
GIERSCH: Yeah. Oh yeah, I've looked at a lot of these.
JOYCE: I mean, that's smaller than a match head.
GIERSCH: Yeah, exactly. It's charismatic microfauna.
JOYCE: Charismatic may be a stretch, but micro for sure. Lednia tumana is a stone fly. It spends part of its life in streams, but only icy streams in these mountains. The fly eats algae and other tiny organisms in the streams, and other insects and birds eat them. They're part of a larger food web. Pull out one string, says ecologist Daniel Fagre, and the web starts to come apart.
DANIEL FAGRE: In only a few decades, we're going to lose all the glaciers here. And they've been persistent on this landscape for at least 7,000 years. So suddenly, you're having a profound change in just a few decades. And that's very difficult for many organisms to adapt to.
JOYCE: What's happening is that as average temperature increases here, the snow and ice retreat up the mountain to colder air. Fagre's colleague Clint Muhlfeld says, eventually, the ice and the insects will run out of mountain.
CLINT MUHLFELD: You know, there's nowhere to go. They're at the top of the continent - the water tower of the continent, and it's squeeze play.
JOYCE: Moving farther down the mountain, you can see more signs of this disruption in the way water works here. In and around Montana's Flathead Lake, for example - one of the biggest lakes in the country - Jack Stanford runs the Flathead Lake Biological Station. He spent decades studying the complex interactions of plants, animals and water.
JACK STANFORD: The way in which water is deposited first and then transported by the rivers is fundamental to the distribution and abundance of organisms.
JOYCE: Organisms that are important not only to nature but to people, too. Take salmon. Salmon lay eggs in the gravel of streambeds. But if you get a warmer spring, you get flash floods. That's because the rain comes in before the snow has melted. It's called a rain-on-snow event. It's like rain falling on pavement. It creates floods that wash the young salmon away and decimates the population.
STANFORD: The way it plays out is that the food web gets a shakeup. The bottom line is that some players in that complex food web will be winners and some will be losers.
JOYCE: Stanford says humans have already altered the natural world in unpredictable ways. Climate change is like putting another pair of dice in play. Christopher Joyce, NPR News.