Danger in Degrees: Goodbye wildflowers, hello sagebrush
In summer, the hillsides above Crested Butte look like a painting by Claude Monet. Reds, yellows and blues are dabbed everywhere brilliantly on a canvas of green. This is, says the state Legislature, the wildflower capital of Colorado. But on a small plot of land several miles from Crested Butte, at the old mining hamlet of Gothic, is a peek into a less colorful future. There, within the grounds of the Rocky Mountain Biological Laboratory, an experiment is being conducted that attempts to predict how global warming will change mountain meadows during the next 50 to 100 years. The experiment is far from complete. But John Harte, a professor from the University of California at Berkeley, says it’s already evident that these meadows and others like them will probably become less colorful. “One thing we can project from this experiment is that in under 50 to 100 years of warming, we are likely to see our meadows looking different,” says Harte, who has been supervising the experiment for 14 years. “They will be less flower-laden, less colorful and replaced by plants that you associate more with lower elevations, sagebrush in particular.” In other words, the hills around Crested Butte will become more like those around Gunnison. Ski towns will look more like ranch towns. Upvalley will look more like downvalley.
Mountains as barometersHarte’s experiment near Crested Butte is but one small part of the big picture that is now being assembled about how higher temperatures will affect mountains. Mountains, because they are so sensitive to changes in temperature, offer early indications of what may come to pass around the world. However, predicting changes in mountainous areas has not been easy. Computer models created by climate scientists do a good job of explaining the temperature and precipitation records from the last century. Assumed increases of greenhouse gas emissions are then plugged into the programs to yield projections of how the climate will change. This work so far has yielded broad brushes predicting changes across continents and oceans. However, these models do not offer the detail of smaller areas such as the American West. Mountains, with their many weather-changing rumples, became even more a matter of conjecture. “Sometimes, trying to get the details right on global warming is like trying to paint the Mona Lisa with a 4-inch house brush,” says Dr. Jerry Mahlman, a climate scientist from Boulder who spent more than 30 years in climate modeling at Princeton University.
Warmer temperatures are the only odds-on favorite. Far less certain is how much precipitation will be received. Some models project that Sun Valley and Jackson Hole will likely get more precipitation, while the Colorado Rockies will get less. But even if Colorado gets just as much water as now, warmer temperatures mean higher evaporation rates. In other words, hotter means drier. This sets up other changes through what scientists call feedback mechanisms. Less snow on the ground means less solar radiation will be reflected back into the atmosphere. Instead, the sun’s heat will be absorbed by the darker soil and plants. That, in turn, will create more heat on the Earth’s surface that will further raise temperatures. That feedback mechanism is the subject of data that will be collected during the next several years in the once-icy fastness of the San Juan Mountains around Silverton. Evidence in hand Already, anecdotal evidence of weather that could be part of a more broadly changing climate is found in almost every quarter. For example, the temperature dipped below zero only seven times last winter, part of at least a short-term trend toward warmer winter nights. (Longer-term data are unavailable.)
These warmer nights might be part of a short-term weather fluctuation, but scientists do say that global warming can be expected to make winters warmer in the mountains, particularly at night. In Aspen, the city’s environmental affairs office reports that the frost-free season has expanded by 22 days since reliable record-keeping began at the city’s water treatment plant in 1949. Most of the gain in warmth has come in the spring. Again, this fits with reports elsewhere in the Rockies that marmots are emerging from hibernation on average 23 days earlier than they did in the late 1970s. That coincides with an increase of average May temperatures of nearly 2 degrees Fahrenheit over the same time period, according to a National Academy of Sciences report. Some evidence suggests the higher the elevation, the greater the change. Support for this theory has been found in an atrophying glacier in Wyoming’s Wind River Range. There, near the summit of 13,745-foot Fremont Peak, ice cores taken from a glacier show alpine temperatures rising more than 6 degrees in the past 40 years, a rate of change far greater than what’s found at lower elevations. “High elevations do seem to be experiencing higher rate of temperature change,” says U.S. Geological Survey scientist David Naftz, principal author of the report.
This disproportionate increase, if in fact it is occurring broadly, might also explain the disappearance of pikas from several mountain ranges in the Great Basin. Small, stubby-eared mammals that emit high-pitched squeaks, pikas are found in above-timberline habitat. Pushed higher by increased temperatures, some ecologists theorize, the pikas have no place to go. Vegetation is also marching higher. In Yellowstone National Park, the whitebark pine is moving up toward the summits of mountains. That changes the scenery, but also affects animals. Grizzly bears eat the seeds of the whitebarks. No time to adaptChanges in vegetation will produce changes in animals in many ways, according to a recent study. As reported in Yale’s Journal of the School of Forestry and Environmental Studies, the study focused on projected changes at eight parks in the United States, including Glacier, Yellowstone and Yosemite. Warmer temperatures, says Oswald Schmitz, professor of population and community ecology, will cause an influx of new species into these parks. In the short term, this means more biodiversity in these parks. However, that crowding may cause the demise of some species – or worse.
“There’s no guarantee the ecosystem won’t simply collapse,” says Schmitz. While plants and animals have adapted to climate change before, the problem is the rate of change being forced by the spewing of greenhouse gases into the atmosphere. “Animal and plant species don’t have enough evolutionary time to adapt,” Schmitz says. These changes are illustrated in a Colorado State University study projecting effects of global warming in Rocky Mountain National Park. Elk populations might actually expand, at least if global warming produces more summer rains. But white-tailed ptarmigan, an above-tree-line species that is already struggling, will probably die, according to the study. Warmer summers depress the success of nesting, as well as survival of adults. This species likes cold and alpine tundra. Of course, tundra will also shrink. It would take centuries, but the scientists envision the vast expanses of unencumbered tundra eventually being replaced by trees.
As for the merchants in the gateway community of Estes Park, hotter and longer summers will mean more customers – to a point. Too hot and summer becomes a bust for merchants. That’s generally true across the world, say scientists. There will be both winners and loser in the early stages of global warming. In the long term, they say, everybody will lose. A big deal In his cabin near Crested Butte, Harvard-trained John Harte has studied the grand panorama of the Colorado Rockies since 1977, when he first began visiting the Rocky Mountain Biological Laboratory to study the effects of acid rain. Gentle and gracious, the 64-year-old Harte is by no means dour, even if his predictions for the effects of global warming are. Harte began his experiment on Jan. 4, 1991, after two years planning. The heat lamps he uses to warm the wildflower meadow year-round had been designed for a farmer in Pennsylvania to keep chickens warm in winter. Instead of chickens, the heat filament strung 5 feet above the ground warms the plants and soil. It’s not glowing red hot, but it continues day and night, winter and summer.
The lamps heat the soil about 4 degrees Fahrenheit, which is a relatively modest projection of the global warming expected later in the 21st century. A 4-degree change doesn’t sound like much, until you consider that the last time Ontario was covered with ice sheets a thousand feet thick and ice sheets spilled into New York and Wisconsin, the temperature was only 15 degrees colder. In other words, there is danger in degrees, or at least change, whether colder or hotter. After the ice left, a whole host of species across North America died for reasons that at least partly had to do with climate change. One thing Harte has found is that computer models very likely understate the warming that could be ahead. Just as the climate affects the ecosystem, the ecosystem can affect the climate. Sagebrush absorbs less carbon than wildflowers, causing more carbon dioxide to be in the air. More carbon dioxide causes more warming. This is one of many feedback mechanisms that suggest the computer models, with their predictions of substantial increases in warming, understate how much temperatures will rise. This discovery about feedback, says Harte, “is the most exciting thing that is going on scientifically” in his experiment. Scientifically exciting, yes, but not a happy discovery for wildflower lovers.
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