A new study reveals human activities have drastically altered the Great Salt Lake’s ecosystem over the past two centuries. Research shows the impact of settlers and a railroad causeway on this ancient ecosystem. Let’s learn more.
For thousands of years, Utah’s Great Salt Lake has adapted to changes in climate and water levels. However, a new study has found that human activities over the last two centuries have led the lake into a state it hasn’t been in for at least two millennia. Recent research by Professor Gabriel Bowen, a geoscientist at the University of Utah, examined sediment samples from the lakebed to better understand how the lake has evolved since it took its current form. These sediments act like a natural archive, preserving information about water, nutrients, and carbon that flow into the lake.
“Lakes are great integrators. They’re a point of focus for water, for sediments, and also for carbon and nutrients,” said Gabriel Bowen, a professor and chairman of the Department of Geology & Geophysics. “We can go to lakes like this and look at their sediments and they tell us a lot about the surrounding landscape.”
Why Is the Research Important
Due to a long-term drought, the lake’s water level has dropped significantly. This is a serious concern for the delicate ecosystem that depends on it. Although scientists already knew about major changes in the lake over tens of thousands of years, Bowen’s study focuses on a specific period, the past 8000 years, and especially the time since European settlers arrived in the mid-1800s.
For the purpose of study, Bowen analyzed two sets of sediment samples. The first came from a 10-metre-long core drilled in 2000. It contains data from about 8,000 years ago. The second one was from a more recent US Geological Survey project. It covers just the top 30 centimetres, representing the past few hundred years.
Two Major Human Influences
From this data, Bowen identified two major human-induced changes in the lake’s history:
1. Mid-1800s – Arrival of Mormon Settlers:
In 1847, Mormon settlers started farming in the area using irrigation, which transformed the land and altered the lake’s carbon cycle. More organic material from plants began flowing into the lake. This shift is clearly visible in the carbon isotope data, which moved away from values associated with rock weathering, such as limestone, and towards those connected to plants and soil.
2. 1959 – Construction of the Railroad Causeway:
In the mid-20th century, Union Pacific built a 20-mile causeway across the lake to support a railway line. This structure separated the North Arm, which has no rivers, from the South Arm, which receives water from three rivers. This division drastically changed how water moved and evaporated across the lake.
Also, it made the South Arm’s water less salty than it otherwise would have been. These delayed problems caused by falling water levels and increasing salt concentrations.
A Transforming Lake
Over the past 8000 years, the Great Lake has largely been in a drying phase. It is slowly shrinking due to high evaporation. The research shows that while natural changes have shaped the lake for millennia, recent human actions have had a much more dramatic and lasting impact.
Bowen says, “If we look at the longer time scale, 8,000 years, the lake has mostly been pinned at a high evaporation state. It’s been essentially in a shrinking, consolidating state throughout that time. And that only reversed when we put in the causeway.”
The findings were published in Geophysical Research Letters on July 22, in a paper titled “Multi-millennial context for post-colonial hydroecological change in Great Salt Lake.” Bowen was the sole author and was supported by grants from the National Science Foundation.