Some effects of climate change are dramatic and visible, like wildfires and extreme weather, but a new University of Colorado Boulder study found that climate change can impact even hidden places and some of the state’s smallest residents.
Pikas are small mammals that inhabit rocky, high-elevation habitats in Colorado. Unlike many small mammals, they don’t hibernate, but use other adaptations to survive winter conditions. Pikas collect “haypiles”, stocks of vegetation to feed themselves in winter. They have thick fur with no bare spots and don’t sweat or pant.
Pika habitats may be bitterly cold in winter, but can get hot in summer. Because they have so few physiological ways of shedding excess body heat, they cool down using rock shelters that lie just below the surface called taluses. These landforms create subsurface “microclimates” that offer milder temperatures.
Talus microclimates give pikas the opportunity to escape summer heat, but a recent Colorado study shows that these refuges may be disappearing.
Chris Ray is an ecologist at CU Boulder studying how animal and plant populations change. She discovered data from the 1960s that included temperatures of both talus microclimates and the air above ground in a pika habitat. This presented a unique opportunity.
The effects of climate change take place over long stretches of time, so having historical data to compare to modern data can demonstrate how climate has or hasn’t changed, according to Ray. Even more fortunate than the age of the dataset was the kind of information it contained.
“It’s very rare to have very old data on microclimate,” Ray said. “1963 (through) ’64, we have a lot of climate data from back then, however those data are almost always taken at 1.5 meters above ground. It’s very rare to find any kind of data taken in the subsurface.”
Ray and her team hypothesized that because microclimates buffer temperature, the temperature change between historical and recent periods would be smaller in the taluses than above ground. They also predicted that the subsurface temperature change would be smallest in winter months because of the insulating quality of snow.
To their surprise, the data showed that microclimates experienced greater temperature increases than above ground. They also found that, both in the taluses and above ground, the increase between periods was greatest in the winter.
The reason for these changes is still unknown, but the possible impacts are clearer. If taluses are rapidly heating, concerns go beyond pika conservation. Cool air collects in taluses and preserves permafrost in the underlying soil. In late summer, permafrost melts, replenishing reservoirs when they’re lowest. If taluses are getting warmer, especially during winter, this important process could be lost, Ray said.
“Understanding how the temperature regime in these landforms is changing could be key to understanding what’s going to happen with our future water resources,” she said.
One caution that Ray offers is the small sample size in her study. Only one year of historical data, 1963-1964, was available. The data collected at the site that year could have been anomalous and not reflective of the overall climate. However the historical data are consistent with temperature records from surrounding weather stations, according to Ray.
“We don’t think the weather in 1963 through1964 was anomalous, but still I’m not comfortable saying, ‘This is how it was’ based on one year,” she said.
Ray argues that her study still raises the possibility that climate change could be having surprising impacts. “I think it’s really important to get this result out there and have people investigate it further, but I don’t think it’s the final word,” she added.