December 12, 2014

A cold-loving insect confronts a warming world

by Julia Rosen

Today marks the end of two weeks of climate negotiations in Lima, Peru, where world leaders gathered to address the growing threat of climate change. Much of the conversation at the UN conference revolved around the urgency of reaching an international agreement to lower global emissions of carbon dioxide and other heat-trapping greenhouse gases. But for some species, such an accord may come too late.

You’re probably picturing polar bears clinging to teetering icebergs, but many other species feel the pressures of a warming world too. Mountain-dwelling critters are particularly vulnerable – as temperatures rise, they must seek higher and higher ground that offers less and less habitat. Imperiled animals include tiny elephant-eared mammals called pikas, which live in fortresses of alpine rubble, and rosy finches, dainty songbirds with an affinity for high-elevation tundra.

Now, a study led by scientists at the United States Geological Survey explores how climate change has affected another easy-to-miss species: the western glacier stonefly, Zapada glacier. This aquatic insect, which could sit comfortably on your fingernail, lives only in the frigid streams of Montana’s Glacier National Park. Scientists predict the park could lose the last of its eponymous ice by 2030, and as the glaciers go, so goes the stonefly.

The rare western glacier stonefly lives in Glacier National Park and thrives in its icy streams. (Credit: Joe Griersch, USGS)

The study was motivated in part by calls to protect the stonefly under the Endangered Species Act. Scientists knew little about the range and health of the insect, so they decided to investigate. Researchers returned to streams that had hosted populations of Z. glacier during surveys conducted in the 1960’s and 1970’s, but this time, they found the insect in only one of the six creeks where it used to live.

The scientists attribute this loss of habitat to environmental changes. The stonefly requires water temperatures that hover just above freezing. But since the 1960’s, air temperatures in the park have increased by 0.7 to 1°C and glaciers have shrunk by a third. In response, the insects inched ever upward, closer and closer to the fast-retreating ice.

“Soon there will be nowhere left for the stonefly to go,” said Joe Giersch, the lead author of the study, in a statement.

As the researchers searched the park, they did find the stonefly in two high-elevation areas where they hadn’t noticed them before, and they spotted nymphs that look like Z. glacier in an alpine lake in Wyoming’s Grand Teton National Park.

However, the scientists don’t think this is evidence of the stonefly expanding its habitat. Rather, they say they probably missed them on their first surveys. These far-flung populations may represent the last holdouts of a species that flourished during colder climates of the past, like the last glacial period.

USGS scientist Joe Griersch stands at the one stream where the stonefly was found. (Credit: Joe Griersch, USGS)

Now, the stonefly has retreated to a few places scientists call refugia – the plural form of the word refuge. Throughout geologic history, refugia have helped species survive periods of unfavorable environmental conditions. But the downside of the small, disconnected populations that persist in refugia is their low genetic diversity, which makes them more susceptible to disease and less able to adapt to new challenges. Indeed, the scientists found evidence for reduced genetic diversity in the insects they studied.

This research highlights how a global problem like climate change plays out on the smallest of scales. In Lima this week, negotiators focused mostly on large-scale questions of how to effectively and equitably reduce emissions. But that doesn’t mean the insect’s story doesn’t contain a message worth pondering.

In his speech before the delegates on Thursday, US Secretary of State John Kerry discussed the options that lay before the international community, and the reasons to take swift action.

“Now I know it’s human nature at times to believe that mankind can somehow defy Mother Nature,” Kerry said, “but I think it is the plight of humanity that, in fact, we cannot.”

Somewhere in Montana, a stonefly is toasting to that.



Explore how life evolves in response to environmental changes in our module on Adaptation.

Learn more about stoneflies from North Carolina State University.

Read more about the study in the Los Angeles Times.

Julia Rosen

Written by

Julia Rosen is a freelance science writer and PhD student at Oregon State University. She received a Bachelor’s degree in Geological and Environmental Sciences from Stanford University before beginning her doctoral research on polar ice cores and climate change. In between, she did her “Master's” in backpacking around the world and skiing. Julia is a periodic contributor to Oregon State’s research magazine, Terra, and helps write blog content and develop learning modules for Visionlearning.

The views expressed above do not necessarily represent those of Visionlearning or our funding agencies.