Peak Blush

The mountaineering community is rallying around a citizen-science initiative to track the growing phenomenon of “pink snow.”

Text—Mark Mann

Robin Kodner was buying a new bike in Bellingham, Washington, last year when the cashier did a double take. “Wait,” he said. “Are you the snow algae lady?!”

Kodner never imagined that her fascination with an ancient single-cell organism would bring her any sort of celebrity. But when the Western Washington University biologist launched The Living Snow Project in 2018, her call for volunteers to collect data from remote mountaintops instantly captured the enthusiasm of the backcountry community.

Mt. Baker-Snoqualmie National Forest, Washington, Photo: ©2018 Sean Gorton (Evenfall Photographers)
Mt. Baker-Snoqualmie National Forest, Washington, Photo: ©2018 Sean Gorton (Evenfall Photographers)

Within 10 minutes of making her first post on Instagram, Kodner received over 100 applications to participate. Two years later, hundreds more have joined in.


“There are a lot of young people who want to get rad in the mountains,” she says, reflecting on the project’s popularity. The sites where snow algae appear are often extremely difficult to reach, but many of the people already going to the trouble of visiting those places are eager to find more purpose in their backcountry travels. “The fact that I made it easy for them to contribute to our knowledge about a system that is understudied, that’s motivating.”

The Living Snow Project is a citizen-science initiative to monitor “pink snow” in alpine environments. Many in the high-altitude crowd will have spotted the phenomenon: occasional blooms of watermelon-coloured snow, seeping across the white plains that cover tall mountains. The pink stains are caused by a type of algae — counterintuitively, a member of the green algae family — that lives in snow and emits a red pigment when the sun is strong. By all accounts, they are eerily beautiful.

“If you’re an observant person and you’re interested in nature, when you see a bloom of pink snow, it’s really striking,” Kodner says.

Petermann Island, Antarctic peninsula Photo: © Franklin Wattecamps

A hero’s journey

It’s easier to fall in love with algae than you might imagine. In the ongoing drama of life on earth, algae play a starring role, while we Homo sapiens, by comparison, have so far only managed a brief and disastrous cameo.

Algae evolved photosynthesis long before plants even existed, some 2.5 billion years ago, thereby oxygenating the atmosphere. Today, ocean algae are responsible for half the photosynthesis that currently takes place on earth. They can also take partial credit for kicking off the Anthropocene era. Much of the petroleum extracted by oil and gas companies today was formed from the biomass of long-dead algae, compacted into the seabeds of ancient oceans. They may soon steal the show yet again: ocean algae sequester massive amounts of carbon, and scientists are now looking to them as a potential key tool in the fight against climate change.

Petermann Island, Antarctic peninsula Photo: © Franklin Wattecamps


Kodner was so transfixed by algae’s outsized influence on our biosphere, she did her Ph.D. dissertation at Harvard University on the deep evolutionary history of algae. She also wanted to find a way to improve our understanding of how the planet is changing: “I wanted my work to be contributing to something.” Using the new tools of DNA sequencing, she started to revisit previously unanswerable questions about how these microbial communities are responding and evolving with respect to climate change.

Pink snow covered glacier
Petermann Island, Antarctic peninsula Photo: © Franklin Wattecamps

Disappearance loop

Snow algae need liquid water as part of their life cycle, so they bloom when the snow starts to melt. In so doing, they darken the snow’s surface and increase the amount of solar radiation that’s absorbed, prompting further snowmelt.

Algae have lived in snow for hundreds of millions of years, but global warming is throwing the balance out of whack, Kodner explains: increasing the rate of melt increases the bloom, which creates a positive feedback loop that accelerates the whole process.


The threat of disappearing snow looms large. “Our ice caps and glaciers are incredibly important to the water cycle of our whole planet,” Kodner says. Losing all that snow and ice would dramatically impact not only freshwater resources for people, but also alter ocean circulation at a fundamental level. “Snow algae can have a quantitative impact on the way these systems operate, and climate change is likely changing the dynamics of snow algae blooms.”

Pink snow on Petermann Island, Antarctic peninsula
Petermann Island, Antarctic peninsula Photo: © Franklin Wattecamps

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