Utah’s Great Salt Lake has always been a barometer of environmental change. But new research reveals that over the past 200 years, human activity has pushed this iconic body of water into a state unlike anything seen in the past two millennia.
By studying carbon and oxygen isotopes preserved in lakebed sediments, geoscientists have pieced together a dramatic story of how agriculture and railroad construction reshaped the lake’s chemistry, salinity, and ecological balance.
“Lakes are great integrators. They’re a point of focus for water, for sediments, and also for carbon and nutrients. We can go to lakes like this and look at their sediments, and they tell us a lot about the surrounding landscape,” said Gabriel Bowen, professor and chair of the Department of Geology and Geophysics at the University of Utah, in a press release.
Published in Geophysical Research Letters, the new study not only uncovers how the lake has responded to climate and human pressures over time but also highlights the fragile future of terminal saline lakes worldwide.
Isotopes Unlock 8,000 Years of History
To dig into the lake’s rich history, researchers analyzed two sets of sediment cores. The first core captured nearly 8,000 years of history, stretching back to when the vast freshwater Lake Bonneville shrank into the modern Great Salt Lake. The second core represented only the past few centuries, covering the critical window when European settlers transformed the watershed.
Carbon isotopes revealed shifts in how organic matter entered and cycled through the lake, while oxygen isotopes helped reconstruct the delicate balance between evaporation and inflowing water. Together, these chemical signatures offered a powerful timeline of environmental change.
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Human Impact on the Great Salt Lake
The sediment record showed two profound disruptions from the past 200 years, both driven by human actions.
The first occurred in the mid-19th century and involved a Mormon settlement in 1847. After this settlement, irrigation agriculture rapidly expanded around the Great Salt Lake. Farming greened the desert landscape, increased the amount of organic matter in the lake, and significantly altered its carbon balance.
The second disruption was more recent, occurring around 1959 with the construction of the Union Pacific railroad causeway that divided the lake’s north and south arms. This human-made barrier disrupted natural water exchange, resulting in a sharp shift in salinity and balance, which are changes never before seen over thousands of years of the lake’s natural variability.
Why Sediment History Matters for the Future
Today, the Great Salt Lake is at the heart of ecological, economic, and cultural conversations in Utah. Once a sprawling inland sea, the lake is now shrinking toward historic lows, threatening migratory bird populations, brine shrimp industries, and air quality.
What makes this new study critical is its ability to connect today’s crisis with a much deeper history. While scientists have long understood the lake’s ancient transformations and are carefully monitoring its current drying, the middle scale — the past few centuries of human-driven change – was less clear until now.
“We have all these great observations, so much monitoring, so much information, and interest in what’s happening today. We also have a legacy of people looking at the huge changes in the lake that happened over tens of thousands and hundreds of thousands of years. What we’ve been missing is the scale in the middle,” said Bowen in the press release.
That missing record now tells a sobering story: humans have already pushed the Great Salt Lake into conditions unseen for millennia. Researchers hope the new information will help with the successful management and conservation of the lake going forward.
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