Microplastics in Lake Tahoe: How Plastic Reaches the Backcountry
After living in Lake Tahoe for more than 35 years, I’ve watched a lot of attention go toward protecting the lake’s clarity and water quality. Most of the pollution we talk about is fairly easy to understand: runoff from roads, sediment entering the lake, trash left on our beaches or pollutants carried in through the watershed.
Microplastics are different because we can’t usually see them, and increasingly, scientists are finding them in places that seem far removed from the obvious sources of plastic pollution, including the mountains surrounding Tahoe. This summer, the 5 Gyres Institute, Tahoe Rim Trail Association and Keep Tahoe Blue are working on a research project studying plastic pollution along the Tahoe Rim Trail. Researchers and volunteers are collecting samples from the air and soil, conducting litter surveys and looking at how tiny plastic particles move through the Tahoe Basin. It raises an interesting question: How does plastic end up thousands of feet above Lake Tahoe in the first place?
Microplastics are plastic particles smaller than 5 millimeters. Some begin as very small particles, while others come from larger plastic products that gradually break apart through sunlight, wind, water and physical wear. Unlike organic material, plastic doesn’t simply decompose and disappear. It breaks into progressively smaller pieces.
Those particles can come from sources we would expect, including bottles, packaging and other litter, but they can also come from things that are much less obvious. Synthetic clothing is one example. Fleece jackets, polyester shirts, nylon outdoor gear and other synthetic fabrics shed tiny fibers as they are worn and washed. Researchers are now studying whether outdoor recreation itself contributes some of those fibers to trails and nearby areas. The plastic found in Tahoe’s high elevations also doesn’t necessarily have to originate here.
One of the more surprising areas of microplastic research involves atmospheric transport. Tiny plastic particles and fibers can become airborne and travel with wind before eventually settling back to Earth. Previous scientific research has documented what is sometimes called “plastic rain,” with microplastics deposited in remote and protected areas far from major population centers.
That is one reason the Tahoe Rim Trail project is looking beyond what is already in the lake. Researchers are studying air, soil and backcountry water together to better understand how plastic moves through the environment. Water falling as rain or snow in the surrounding mountains eventually moves downhill through soil, streams and groundwater toward the lake, so understanding what is present higher in the watershed may help researchers better understand what ultimately reaches Lake Tahoe.
This isn’t the first time microplastics have raised concerns here. In 2023, a large international study published in Nature examined surface waters from 38 lakes and reservoirs around the world and found plastic particles in every lake studied. Lake Tahoe received considerable attention because its concentration of plastic particles in that particular study was among the highest reported, ranking third out of the 38 lakes and reservoirs studied, despite Tahoe’s relatively small permanent population and extensive environmental protections.
That result was especially surprising because the lakes with the highest concentrations generally fell into two categories: heavily populated and urbanized lakes, or large lakes with characteristics that allow plastics to accumulate. Local scientists have been studying the issue for several years as well. Researchers with the Tahoe Environmental Research Center and Desert Research Institute have looked at potential sources including streams, storm drains, snow accumulation and even dryer vents. Other work has examined where plastic particles go once they enter the lake, including surface water, deeper water and sediment.
There are still a lot of unanswered questions, particularly about where Tahoe’s microplastics are coming from and how they move through the watershed. That is what makes the Rim Trail research particularly interesting.
The current project is 5 Gyres’ first land-based, high-elevation scientific expedition. The organization is better known for ocean research, including expeditions studying plastic accumulation in the world’s major ocean gyres. This time, the Tahoe Basin is the focus. By sampling around the Rim Trail, including elevations above 9,000 feet, researchers hope to better understand plastic pollution throughout the basin rather than looking only at what is already in the lake.
The project is also examining litter found along the trail and the possible role of synthetic outdoor gear. Ultimately, 5 Gyres says the research is expected to contribute to a detailed report and a peer-reviewed scientific paper. I think it is important not to get ahead of that research. We know microplastics are present in Tahoe, and scientists have identified several plausible ways they can enter and move through the environment, but determining exactly how much comes from local recreation, airborne particles, runoff or other sources is a much more complicated question. That is precisely why this research is being done.
For anyone interested in the subject, there is a timely opportunity to hear directly from the scientists involved. On Thursday, August 27, the Tahoe Rim Trail Association, 5 Gyres Institute and Keep Tahoe Blue are hosting a panel discussion called “The Tahoe Rim Trail Expedition: Tracking Plastic Pollution from Trail to Lake.”
Researchers will discuss the project, field sampling, initial findings, atmospheric transport, synthetic gear and what this research may tell us about the movement of plastic through the Tahoe watershed. The reception begins at 3:30 p.m., followed by the panel discussion from 4 to 6 p.m. at the Spurlock/Evers Environment & Education Center in South Lake Tahoe. See the link in the featured article below.
Microplastics are obviously not the only issue affecting Lake Tahoe, and scientists are still working to understand their long-term ecological significance. But the possibility of plastic showing up not just along our beaches, but in the air, soil and water of Tahoe’s backcountry, gives us another reason to look at how the things we do as a society are affecting our environment and, ultimately, the lake.
Get In Touch
