Results from Longstanding Collaboration of UW, Duke Professors Published in Nature
While in graduate school at the University of Washington in the late 1980s, Dan Doak and Bill Morris built a friendship that has continued into their professional careers.
After the two became professors on opposite sides of the continent -- Doak was first in California before coming to the University of Wyoming; Morris is a professor of biology at Duke University -- they began looking for reasons to spend more time in the mountains and hatched a plan to work together on the research of alpine plants in Alaska.
Over the next many years, Doak and Morris gathered evidence that points to a better understanding of how the constellation of effects from changing climates will combine to determine the shifting geographical ranges of species. The results of this now longstanding collaboration was published today (Thursday) in Nature, the world's foremost weekly scientific journal and the flagship journal for Nature Publishing Group (NPG).
As the Earth's climate warms, species are expected to shift their geographical ranges away from the equator or to higher elevations. While scientists have documented such range shifts for many plants and animals, the ranges of many others seem to have remained stable in the face of recent climate changes.
"Half the time, we find species aren't moving yet," says Morris, "but we haven't understood if that means climate change will never affect them or what makes them different from those species that have moved."
By synthesizing the results of six years of research on two arctic/alpine plants-- from the northernmost slope of Alaska to the Canadian Rockies to the high mountains of Colorado -- Doak and Morris are able to show when and why some species' ranges may shift due to climate and what may have led to stable distributions for others.
The research reported in the Nature paper, titled "Demographic compensation and tipping points in climate-induced range shift," arose from a variety of questions about one of the two species, moss campion, that Doak and Morris had already been studying in central Alaska. Moss campion, recognizable by its cushions of pink flowers in the late spring and summer, is also common in the alpine areas of the Snowy Range near Laramie.
"Our earlier work led to a larger and larger set of questions," says Doak, a professor in the Department of Zoology and Physiology at UW. "We realized a really interesting question to ask is, if you look across the whole range of a species, which hasn't been done for many plants or animals, what is it that causes a species to stop living further south or further north than it currently lives."
The two plants are good choices for a study of climate effects because, like all tundra plants, they thrive in cold places and may be especially sensitive to effects of a warming climate -- serving as "canaries in the coal mine."
Doak and Morris found the most unexpected results at the southern edge of their study range. While the plants, not surprisingly, showed negative effects of warmer conditions, the lower survivorship rates there were being offset by much higher growth rates.
"They grow so much faster that it actually compensates for that lower survivorship and the populations still appear on average to be stable," Doak says. "That was a surprise to us."
These compensatory changes can be thought of as sort of a see-saw. On one end, you see more of the smaller plants dying; on the other end, you see those that do survive are growing more quickly, so they can start making flowers and seeds sooner.
"These opposing changes are like a teeter-totter; survival goes down but growth goes up," Morris says.
However, at some point, the teeter-totter may become overstressed. When it breaks in the middle, both ends drop and, "That can happen really suddenly," adds Morris. The researchers also see strong evidence for this outcome in the hottest and driest years of their study.
Doak and Morris' findings explain why these two plants haven't moved much yet, but also indicate that, in the near future, the changes in climate will likely reach a tipping point, beyond which their ranges will rapidly respond.
The ways in which these two plants compensate for climate shifts and the ways in which this ability seems to break down past a tipping point are likely to generalize to other species, meaning their research may help to predict future ecological effects of climate and allow scientists to better plan for such impacts.
Knowing when plants are going to reach a tipping point may also aid "assisted migration," in which species are intentionally moved by humans to locations where the climate is more favorable to them, says Morris.
To gather their data, Doak and Morris logged countless miles -- by plane, by car and by foot. More recently, the scientists have extended their research farther south to the Sangre de Cristo Mountains of New Mexico.
On their southernmost trips, Doak and Morris typically backpack five miles to a camp at about 11,500 feet, then ascend higher into the alpine to conduct their research over five or six days. Their summertime work is often disrupted by lightning, which Doak says forces them to "spend quite a bit of time running off the mountain and then climbing back up to where the plants are."
The researchers' trips to Alaska are far more time-consuming. After flying to Anchorage, Doak and Morris drive some 350 miles to Fairbanks and then another 300 miles, or 8 ½ hours, to their research site in the Brooks Range.
Once there, Doak says, they face another challenge.
"Up there, our worst enemy is snow," he says. "Even a little bit of snow is enough to blanket the ground and we can't find the plants."
Their other Alaskan study sites, in the Wrangell-St. Elias National Park and Preserve in southcentral Alaska, involve similar travel by car and, especially, by foot.
The two researchers plan to continue their work into the foreseeable future, with the support of a long-term grant from the National Science Foundation.
"To understand climate effects, it is important to see what happens across many years," Doak says. "As we all know, the weather is different every year."
How long will they keep up their work?
"Until our knees finally give out," Morris says.
All this travel and research means more time beside each other in a car and in a tent. Luckily, Doak says, the two researchers are friends.
"One of the funny things about this project is, you couldn't do it with somebody you didn't like," he says. "We've worked together on these plants since 1995, and that's far longer than many people stay married, let alone do a single scientific study with a colleague."