Warming Sign? Another Early Spring for Rocky Mountains

John Roach
for National Geographic News
April 9, 2007
Spring is coming early to the western slope of Colorado's Rocky
Mountains, providing continuing signs of a warming world, according to a
conservation biologist.

"I'm anticipating there'll be some flowering again in April this year, which is something that never used to happen," said David Inouye, a professor at the University of Maryland in College Park.

This will be Inouye's 37th season at the Rocky Mountain Biological Laboratory (RMBL) in Gothic, outside the resort town of Crested Butte (see Colorado map).

Dozens of scientists make the annual trek to a meadow at RMBL about 9,500 feet (2,900 meters) above sea level to study everything from wildflowers to marmots (see a picture of a marmot).

Many of the studies indicate a warming planet.

In addition to the early flowers, robins return earlier from their wintering grounds, and marmots, chipmunks, and ground squirrels emerge earlier from hibernation than they once did, the scientists say.

Low Snowpack

It is also another year of light snowpack on the western slope, despite heavy snowfall elsewhere in Colorado, Inouye said.

Last winter's blizzards mostly struck the eastern part of the state, but RMBL is west of the Continental Divide and had a relatively dry winter, he explained.

The low snowpack is consistent with a trend that began in 1998, when a long-term climate pattern known as the North Pacific Oscillation spurred a dry phase in the region.

Since then, six of the last nine years have yielded a lower than average snowpack at the study site, according to Inouye.

The dry phase, he added, coincides with a long-term global trend toward warmer air temperatures. This has allowed some elements of the ecosystem at RMBL to respond in synch.

For example, marmots, which scientists hypothesize are cued by temperature to emerge from hibernation, are now more likely to find plants to eat when they wake from winter's slumber.

Through most of the 1990s and in two of the last nine years, the burrowing rodents emerged early but found the ground covered in snow.

"The problem of coming up earlier in heavy snow years is that they starve and they get killed by predators because they have no safe places to go," said Dan Blumstein, a biologist at the University of California at Los Angeles who studies marmots at RMBL.

(Blumstein's marmot studies are sponsored by the National Geographic Society. National Geographic News is part of the National Geographic Society.)

But for the last six years, he noted, the marmots at RMBL have experienced a population explosion. There are more marmots now than there have been since studies on the population began in 1962.

The population boom, earlier emergence, and warmer temperatures lead Blumstein to ask: Is climate change good or bad for marmots?

"I don't know," he said.

Previous studies found that high rates of marmot death are associated with summer droughts, Blumstein said.

If summer rains fail to fall, the marmots at RMBL either starve to death or forage for green vegetation in areas where they are vulnerable to predators, he explained.

The last five summers have been wet during July and August.

"If climate change influences summer drought, then I think it could be death [for the marmots]. I think that's going to be the mechanism," he said.

Plant Risks

While the early snowmelt is, for the moment at least, a boon for the marmots, the trend is proving risky for plants that now bud well before the last of the late-season frosts hit.

Inouye explained that the early snowmelt allows plants like aspen sunflowers to begin growing in late April or early May, instead of the middle or late May.

"The growing season starts early, but we're still likely to get hard frosts up until mid-June," he said.

A mid-June frost hits the buds at their most vulnerable.

"So many of the buds are killed by the frost that there are essentially no seeds being made and therefore no seedlings being made," he said.

Though plants like aspen sunflowers live as long as 75 years, the lack of seedlings means the next generation may never sprout, Inouye noted.

Inouye is not sure whether the trend will continue.

"Every year gives us one more data point, and it takes quite a few data points before you can say, Yes, there's a clear trend going on," he said.

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