In 1845, Henry David Thoreau began a two-year stay in a small cabin near Walden Pond in Concord, Massachusetts. In his famed book inspired by the stay, Walden, Thoreau describes the place as a quiet, pristine pond in a wooded sanctuary where he lived in solitude.
But the place has undoubtedly changed; it’s now severely polluted. A new study details just how much humans have impacted the lake since Thoreau reveled in its solitude, Sara Chodosh reports for Popular Science.
Each year, about 500,000 people visit Walden Pond to tour Thoreau’s cabin, enjoy the view offered at the site and take a dip in the lake. To accommodate visitors, the state opened a new 5,680-square-foot visitors center in 2016. But the presence of all these people has its consequences.
The new study, published recently in PLOS One, details just how much visitors have transformed Walden Pond. "I see our results as a wake-up call," says Curt Stager, professor at Paul Smith’s College and lead author of the study, reports Inverse’s Yasmin Tayag.
As Tayag reports, Stager has been studying the mud at the bottom of the pond since 2015 to see how it’s changed. In an initial analysis of changes in sediment composition, the researchers found that the health of the pond declined with the redevelopment of the shoreline in the 1920s, which resulted in increasing numbers of visitors to the region.
The newest study, which includes sediment cores that record 1,800 years of history in their layers, shows a more complete picture of what is going on. Researchers have found increasing numbers of phytoplankton, microscopic algae that thrive in nutrient-rich waters, since the early 1900s. The researchers suggest human waste from swimmers and disturbed sediments from paths to Thoreau’s cabin contributed to the lake's increase in the nutrients phosphorus and nitrogen.
“[Human] wastes, largely from swimmers, now represent about half of the algae-stimulating phosphorus budget of the lake,” Stager tells Tayag. His upcoming book, Still Waters: The Secret World of Lakes, details his research on the area.
While Walden Pond is still relatively clear, the increase in algae “could turn Walden from a beautiful clear lake into a slimy green stew,” Stager tells Inverse.
The phytoplankton could also wreak havoc on the rest of the ecosystem. If the algae continues to grow, it can block sunlight for other pond-dwelling plants, preventing them from getting the light they need to survive. If these plants die, so do many other organisms that rely on them for food.
According to the study, the area may be also increasingly susceptible to future changes in climate. Already we're seeing the effects: Shorter winters and ice melt has had noticeable impacts on Walden's plants, birds and insects, causing them to become active earlier than usual, Tayag reports.
In addition, Chodosh writes, the area is now crowded with cars from visitors, manmade pathways have been created along the pond and people routinely break branches and pick flowers along the paths.
Last year, an exhibition of photographs by S.B. Walker also showcased how Walden Pond has changed since Thoreau’s stay. Documenting the state of the area today, Walker photographed an ice cream cone left on the pavement by a visitor, a family hanging out with snacks nearby and a woman in the water staring at her smartphone.
The damage done to Walden Pond echoes a greater problem that plagues many of the national parks, Chodosh writes. About 44 million people visit national parks annually, and the regions face an array of challenges thanks to this influx of people. Parks like Yellowstone and Yosemite are seeing dramatic changes to their ecosystems. For example, diseases carried in somehow by humans may be to blame for Yellowstone’s decline in wolves and trout.
While the pond won’t ever return to its Walden condition, further damage can be prevented by intervention, Stager tells Inverse, including educating swimmers about pond etiquette.
Perhaps the most important rule to remember: Don't pee in the pond.