28/07/2024
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The Great Salt Lake isn’t just drying out. It’s warming the planet.
The Great Salt Lake released 4.1 million tons of carbon dioxide and other greenhouse gases in 2020, researchers found — more evidence that dried-out lakes are a significant source of emissions.
Snow and water pool on a stretch of exposed lake bed on the southern end of the Great Salt Lake in Magna, Utah, in 2023. (James Roh for The Washington Post)
By Joshua Partlow
Updated July 25, 2024 at 1:39 p.m. EDT|Published July 25, 2024 at 11:00 a.m. EDT
Like some dystopian astronaut, Melissa Cobo would hike the searing flats of the dried-out Great Salt Lake every couple of weeks, hauling a heavy backpack attached by a hose to what looked like the lid of a cake dome. What remained of the lake often seemed out of reach as she struggled through hot mud, clay and a weird crystalline layer that broke with her footsteps onto a greenish muck.
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“You see the water, but you never actually get to it, no matter how many hours you walk,” Cobo said.
Through these grueling treks, Cobo, then a Utah State University graduate student, and her adviser, Soren Brothers, discovered more disturbing evidence that dried-out lakes are a significant source of carbon dioxide emissions — one that has not been included in the official accounting of how much carbon the world is releasing into the warming atmosphere.
In a new study in the journal One Earth, the researchers calculated that 4.1 million tons of carbon dioxide and other greenhouse gases were released from the drying bed of the Great Salt Lake in 2020, the year Cobo and others collected the samples. This would amount to about a 7 percent increase in Utah’s human-caused emissions, the authors found.
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While other researchers have documented carbon emissions from dried-out lakes — including the Aral Sea in Central Asia — Brothers said that his study tried to calculate what part of the emissions from this major saline lake could be attributed to humans, as the Great Salt Lake has been drawn down for human use, a decline worsened by climate change and the West’s megadrought of the past two decades.
“This is the first time we’re saying, ‘This is something that’s on us,’” said Brothers, now a climate change curator with the Royal Ontario Museum.
Lakes around the world normally store carbon. Plant and animal remains settle on the bottom over thousands of years as sediment, much of it in low-oxygen layers that degrade slowly.
“When lakes are inundated with water, let’s say their useful state, they are kind of allies in our struggle for removing CO2 from the atmosphere,” said Rafael Marcé, a research scientist at the Centre for Advanced Studies in Blanes, Spain, who has collaborated with Brothers on prior work but wasn’t involved in this study.
When lakes dry out, oxygen can pe*****te deep into the sediment, waking up microorganisms that start to feast on the organic matter, releasing carbon dioxide, Marcé said.
“The first thing you do when you wake up is have breakfast, right?” he said. “Same for them.”
Researcher Melissa Cobo on the Great Salt Lake in 2020. (Soren Brothers for The Washington Post)
Utah’s Great Salt Lake — the largest saline lake in the Western Hemisphere — has been a buffet for microorganisms in recent years. Lake levels fell to record lows two years ago. It rebounded some after the past two wet winters, but vast stretches of dry lake bed remain, and levels still lie below what state officials consider a healthy range. There are many dangers posed by its diminished state, including toxic dust, loss of habitat for birds, and impact on brine shrimp and other industries.
Brothers and his colleagues used a portable greenhouse gas analyzer to measure the amount of carbon dioxide and methane emerging from different areas of the dry lake bed or in the water.
“As soon as you put that dome on the sand or exposed lake bed you start seeing that CO2 going up,” he said.
Emissions were higher in summer than winter and tended to be lower in places that had been existing as dry land for longer. Marcé, who has been studying the lake bed of the Aral Sea, said some parts of the former lake bed exposed for 60 years are still emitting carbon dioxide. He expects that to continue.
“It’s on the century scale, probably,” said Marcé, who has been working with a group of scientists documenting such emissions around the world.
Both Brothers and Marcé said they wanted to build enough evidence to convince the United Nations to include these types of emissions as countries calculate their carbon inventories.
“They must include the drying lakes in those inventories,” Marcé said. “Because in the case of very big lakes, they could be missing something which is very relevant.”
Dried, cracked mud is visible at the Antelope Island Marina on the Great Salt Lake in 2022. (Rick Bowmer/AP)
Including these as human-caused emissions in national inventories would require a comparison with emissions from these lakes before the drying occurred, said Pep Canadell, executive director of the Global Carbon Project.
International climate agreements aren’t aimed at holding countries responsible for carbon dioxide produced before the past few decades when the accords were reached.
“Although it is fair enough to say it is a missing flux, my initial reaction is that many/some of these lakes probably were dried out many decades ago,” Canadell said in an email.
But if the lake drying happened after such agreements were in place, and was the result of direct human activities such as withdrawing water for agriculture, “then we are certainly missing those fluxes and nations should review their accounting systems,” he said.
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By Josh Partlow
Joshua Partlow is a reporter on the The Washington Post’s national desk. He has served previously as the bureau chief in Mexico City, Kabul, Rio de Janeiro, and as a correspondent in Baghdad.
