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At the Great Salt Lake, record salinity and low water imperils millions of birds

Utah’s Great Salt Lake is smaller and saltier than at any time in recorded history. In July, the U.S. Geological Survey (USGS) reported that the world’s third-largest saline lake had dropped to the lowest level ever documented. And last week researchers measured the highest salt concentrations ever seen in the lake’s southern arm, a key bird habitat. Salinity has climbed to 18%, exceeding a threshold at which essential microorganisms begin to die.

The trends, driven by drought and water diversion, have scientists warning that a critical feeding ground for millions of migrating birds is at risk of collapse.

“We’re into uncharted waters,” says biochemist Bonnie Baxter of Westminster College, who has been documenting the lake’s alarming changes. “One week the birds are gone from a spot we usually see them. The next week we see dead flies along the shore. And each week we have to walk further to reach the water.”

After years of inaction, the prospect of a dying lake, plus the risk of harmful dust blowing from the dry lakebed, is galvanizing policymakers to find ways of restoring water to the shrinking lake.

The Great Salt Lake is really two lakes, divided in 1959 by a railroad causeway. Over time, the northern arm, which has few sources of fresh water, became saltier than the southern arm, which is fed by three rivers. Historically, salinity in the northern arm has hovered around 32%—too salty to support more than microorganisms—and about 14% in the southern arm.

Although the southern part is about four times saltier than seawater, it supports a vibrant ecosystem characterized by billions of brine shrimp and brine flies, which feed on photosynthetic cyanobacteria and other microorganisms. Birds, in turn, devour prodigious numbers of flies and shrimp when they arrive at the lake to nest, molt, or rest during migrations. A diving waterbird called the eared grebe, for example, needs 28,000 adult brine shrimp each day to survive.

The low water and rising salinity threaten to destroy the base of this food web, researchers say. The receding shoreline has already dried out many reeflike mats of cyanobacteria, known as microbialites, that dot the lake bottom. Baxter fears the saltier water now threatens even the microbialite communities that remain submerged. “In laboratory tests, when the salinity passes 17% we see the cyanobacteria start to die off,” she says.

NASA satellite images from June 1985 and July 2022 highlight how Utah’s Great Salt Lake has shrunk to the lowest level recorded since measurements began in the 1840s. Use the slider to see the two images.NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey and data from the National Water Information System

Loss of the mats could harm brine fly populations, Baxter says. The flies lay eggs on the lake surface, producing larvae that swim down to the microbialites, where they pupate before maturing into adults. Some bird species feed on the larvae or adults, whereas others eat the pupae—which have been showing up dead on the lakeshore by the billions during this fall’s migration season.

Soon the brine shrimp could dwindle as well. “The fear is that in some future year, [the lake] will become so salty that its populations … will collapse,” a pair of state ecologists wrote recently.

In the meantime, researchers are mobilizing to track the unfolding crisis. Baxter is bringing in a brine fly expert to assess the situation. Conservation groups are tracking shorebird populations across the intermountain West. And USGS has established a program to monitor hydrology and ecology at other saline lakes in Oregon, California, Nevada, and Utah, which are facing similar stress.

The shrinkage of the lake threatens people as well as wildlife. In a 2019 state-funded report, atmospheric scientist Kevin Perry of the University of Utah estimated that 9% of the exposed lakebed sediments contain problematic levels of arsenic or metals, thought to be derived from industry, wastewater treatment, or agriculture. Winds are likely to erode the crust that holds the sediment in place and carry dust far and wide. With more than 1 million residents living near the lake, in Salt Lake City and its suburbs, the worst-case scenario would be an air pollution disaster—akin to those experienced by communities in Iran near other saline lakes. Even Utah’s famed ski slopes are imperiled by the dust; scientists have documented how storms are already dumping lakebed particles onto the snow, darkening it and hastening the melt.

For years, conservationists have urged policymakers to reduce the water that farmers and other users divert from streams that flow into the lake. But “conventional wisdom has been it’s just a salty lake—we should be using the water upstream,” says Utah State Representative Tim Hawkes. “For many in Utah the lake’s been a little bit out of sight, out of mind.”

This year, however, policymakers sprang into action. In April, Utah Governor Spencer Cox signed a landmark series of bills aimed at rescuing the lake and addressing the drought. They include new rules that allow farmers to sell water rights they are not using to groups that will allow the water to flow to the lake. The state earmarked $450 million for water infrastructure and conservation projects, including a $40 million fund that could acquire water for the lake in the future.

Such policies could take years to have a noticeable impact, especially if the current drought continues. Baxter, for one, wonders: “Is any of this enough?” But Marcelle Shoop, who heads the Saline Lakes Program for the National Audubon Society, says she is “optimistic, because there are so many people trying to develop solutions.”

In the meantime, the lake may get temporary relief from a different source: the upcoming winter wet season. If it produces a good snowpack in nearby mountains, the runoff could help refill the region’s parched streams.

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