Climate change altering alpine ecosystems more rapidly than suspected
High Country News
Outside David Inouye’s Colorado cabin at 9,600 feet, the morning air still smells like yesterday’s rain. Bumblebees, drunk on pollen, drone from one flower to the next, while hummingbirds zip back and forth like tiny fighter pilots to the sugar water Inouye puts out for them. Inouye, a research ecologist from the University of Maryland, stands stock-still on a deck, one hand holding the red plastic hummingbird feeder, the other moving slowly toward it. The iridescent birds ignore him. One hovers at the cusp of the feeder.
Inouye’s hand creeps closer.
Without a sound, he closes it. His grip is firm but not constricting, and the male broad-tailed hummingbird that against all odds finds itself enclosed in a human fist doesn’t seem alarmed. As Inouye carries it through his creaky cabin door, its head peeks out from between his thumb and pointer finger, its black eyes curious, alert.
In his four decades at the Rocky Mountain Biological Laboratory in Gothic, Colorado, Inouye has captured and banded some 500 hummingbirds in an effort to understand their niche in the meadows surrounding his cabin. When he started, he had no intention of documenting climate change. But lately, as its effects have begun rejiggering alpine communities worldwide, Inouye’s research is emerging as one of the strongest indicators that mountain ecosystems are changing more quickly — and more dramatically — than previously suspected. The most compelling evidence comes not from hummingbirds, but from another, unexpected byproduct of Inouye’s patient research: A massive data set on the plants they and other pollinators visit.
Back in the early 1970s, Inouye realized that to understand hummingbirds, he also had to learn about wildflowers. So he and a group of colleagues each plotted out a few patches of meadow in the West Elk Mountains and spent the summer counting the number of blooms there. After a few years, his colleagues had the data they wanted and abandoned their plots. But Inouye, then a Ph.D. candidate at the University of North Carolina, kept plugging away.
Every summer, he returned to the same high-altitude meadows, meticulously recording how many of each species of flowers there were, when they blossomed and when they died back. By 2013, he and his grad students had amassed an unparalleled data set, covering some 2 million individual flowers from 121 species. It was enough to conclude that, since the 1970s, Rocky Mountain wildflower season has lengthened by an average of 35 days.
The implications of that finding — published earlier this year in the Proceedings of the National Academy of Sciences — reach past these particular alpine meadows, to the rest of the Rockies and beyond. “Across the globe, one of the strongest indicators of climate change is the timing of biological events,” says the study’s lead author Paul CaraDonna, a 26-year-old Ph.D. student at the University of Arizona. Other studies have focused just on the date of first flowering, which offers only a half-formed picture of the changes taking place.
To the wildflower enthusiasts who gather each year in the nearby mountain town of Crested Butte — the official wildflower capital of Colorado — an extra month of blooms may seem like the bright side of climate change. But because most alpine species are perennials that can live up to 30 years, “flowering longer could actually have a counterintuitive effect,” CaraDonna explains. “They’re investing so much energy in reproduction that they may actually be growing less.”
Plus, a longer flowering season doesn’t always mean more flowers, because while snowfall tends to melt earlier, the date of winter’s last hard frost hasn’t changed. Many plants are budding sooner, but a solid frost in May or June will still kill them, resulting in years with very few flowers. (Colorado fruit growers face a similar problem: False springs cause orchards to bud too soon, only to have the burgeoning apricots and cherries killed off when wintry weather returns.)
In the alpine zone, that kind of die-off affects bees, butterflies, hummingbirds and other flower-reliant creatures. Broad-tailed hummingbirds like those summering outside Inouye’s cabin, for example, migrate from Southern Mexico to the Colorado Rockies every spring. Their cue to head north seems to come from the lengthening daylight, which means they’ll continue to arrive at roughly the same time regardless of how climate change affects conditions at the northern end of their route. Some years, they may arrive to find hardly any flowers at all. Other years, they may find that peak flowering of the species they depend on has already come and gone.
“The floral landscape is being reshuffled,” CaraDonna says. “It’s like going to a grocery store and getting used to all the food items being in the same aisles, and then you go back and everything’s in a different place.”
With the hummingbird still peering out from his left hand, Inouye uses his right to pour himself a cup of tea. He sips it gingerly before fitting the hummingbird’s leg with a metal band no bigger than a grain of rice and jotting its ID in a handwritten log.
Tall and lanky, with black hair just beginning to go gray, Inouye, now 64, moves with a Zen-like patience. His demeanor is well-suited to the Rocky Mountain Biological Lab, a rustic field station in an old mining camp where some of the country’s longest-running ecology studies take place. Scientists here tend to return year after year, and their pursuits are the stuff of bio-nerd lore: The lab’s only permanent resident, Billy Barr, has turned decades of lonely winter nights into one of the most comprehensive avalanche and snowfall records anywhere, and a project documenting yellow-bellied marmots is so long-lived it’s been handed down from one scientist to the next, like an heirloom. The desire to understand this one place has surpassed science and become a kind of love.
“As humans, we live 60 to 100 years if we’re lucky,” CaraDonna says. “But ecosystems operate on such a different scale. We’ve gotten amazing insight into how natural systems work because we’ve been paying attention to them for so long, and from so many different perspectives.”
Inouye’s own family history at Gothic spans four generations: his father, a physician, volunteered here in the ’70s; Inouye’s son, Brian, has been coming since he was a year old. Now 44, Brian and his wife — fellow biologist Nora Underwood — bring along their daughter, Miyoko, who spends her days catching bugs with the lab’s day camp. If Miyoko returns as an adult, the landscape she’ll see may be hardly recognizable. But thanks to her family’s work, she’ll have access to a detailed record that will help her, and us, understand what’s been lost.
At the cabin, Inouye pads back out to the front porch. He unfurls his hand. A moment later, the emerald bird, weighing about the same as a penny, is sucking nectar from a nearby patch of larkspur. Then it lifts up into the sky, a dark speck against a blue canvas, plummets, and is gone.
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