For over 40 years, the U.S. Forest Service has kept a close eye on high-altitude lakes in Colorado. They’re looking for signs of how human activities and climate change impact these fragile ecosystems.
These mountain lakes are sensitive and can show changes in the environment before other areas do. Mary Jade Farruggia, a researcher at the University of Colorado Boulder, calls them a “canary in the coal mine.” This means they can warn us about changes that may affect larger environments later.
“They react quickly to environmental shifts,” Farruggia explains. “Understanding these changes helps predict future impacts on other ecosystems.”
Recently, Farruggia collaborated with the Forest Service and other researchers to analyze data from 35 lakes in the southern Rocky Mountains. This study used information collected as part of the federal air monitoring program. The goal was to see how climate change and air pollution affected lake chemistry over time.
These efforts tie into federal regulations, like the National Atmospheric Deposition Program, aimed at improving air and water quality in high-altitude areas following the 1977 Clean Air Act.
Since the program started, more than 2,500 samples have been taken from lakes ranging between 9,600 and 13,000 feet. Most of these lakes are located in Colorado, covering various national forests and wilderness areas.
Typically, researchers sample each lake twice a summer, and they are now testing for 19 different chemicals, up from the previous 13. “This long-term monitoring is crucial,” says Farruggia. “As our climate gets more unpredictable, we need extensive data to track changes over time.”
The data might help answer questions about how this year’s unusually low snowpack could affect these lakes. “Some lakes rely heavily on precipitation. They might react strongly to changes in snowpack,” she notes. This information helps environmental managers decide which areas need immediate attention.
Many samples come from volunteers. In the Roaring Fork Valley, a local nonprofit called Wilderness Workshop has been a vital partner since the late 1980s. “These lake datasets give us a long-term view of how these sensitive areas are doing,” says Will Roush, the nonprofit’s executive director. “These headwaters feed countless communities downriver, so their health impacts everyone.”
Last year, budget cuts threatened the program, but Pitkin County stepped in to provide funding for the White River work in 2026. However, Roush emphasizes that ongoing federal support is essential for long-term success.
Why Are Mountain Lake Chemistries Changing?
In a recent webinar, Farruggia shared findings from their ongoing study. She explained that high-altitude lakes are particularly vulnerable due to their clear waters and small watersheds. The study aimed to investigate how air pollution and warming temperatures affect nitrogen and sulfate levels in these lakes.
“Air pollution is the main source of nitrogen and sulfate,” Farruggia explains. “These chemicals can make lakes more acidic, which harms aquatic life and can lead to toxic metals entering the water.” Furthermore, nitrogen can promote harmful algal blooms, making lakes cloudy and uninviting.
While examining regional air pollution trends, they found that only half of the lakes’ sulfate levels and about 30% of nitrogen levels could be explained by these trends. Each lake’s response is influenced by various factors, like geography, size, and land use.
“It’s clear that climate and pollutants matter, but there’s no single explanation for each lake’s chemistry,” Farruggia says. “It’s a mix of factors. Our understanding needs to evolve as we gather more data.”
This ongoing study shows the need for widespread, long-term monitoring. “Climate is becoming more variable and extreme,” she remarks. “Monitoring will help us adapt to changes effectively.”
As we continue to track these sensitive ecosystems, the lessons learned will be vital for protecting the health of our environmental resources.
