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Eroding mountains are leaching CO2 into the atmosphere

"This goes against a long-standing hypothesis that more mountains mean more erosion and weathering, which means an added reduction of CO2," researcher Jordon Hemingway said.

By Brooks Hays
Eroding mountains are leaching CO2 into the atmosphere
Taiwan's Central Range is home to large amounts of erosion. Photo by Robert Hilton/Durham University

April 12 (UPI) -- Eroding mountains can leach carbon dioxide back into the atmosphere, new research shows.

Previous research has shown mountain erosion and rock weathering can pull CO2 from the air as newly exposed rocks react with the atmosphere and form calcite and other minerals. But the latest findings, shared in the journal Science, suggest the erosion process is actually a net contributor of new CO2.

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"This goes against a long-standing hypothesis that more mountains mean more erosion and weathering, which means an added reduction of CO2," Jordon Hemingway, a postdoctoral fellow at Harvard University, said in a news release. "It turns out it's much more complicated than that."

It's not the rocks that are releasing the fresh CO2, but the tiny organisms that are eating the eroded rock. As weathering breaks down rock, trapped organic carbon is released. When microbes feed on these minerals, they release CO2 as a byproduct.

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Researchers discovered the details of the erosion cycle while studying a mountain chain in Taiwan. The country's Central Range boasts some of the most erosion-prone mountains in the world. The mountains' steep rocky sides are hit with several major typhoons every year. Wind, rain and sediment mechanically erode the mountainsides at advanced rates.

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When scientists examined soil samples from across the Central Range, they were surprised to find almost no organic carbon.

"At the very bottom of the soil profile, you have basically unweathered rock. As soon as you hit the base of the soil layer, though, you see rock that's loose but not yet fully broken down, and at this point the organic carbon present in the bedrock seems to disappear entirely," said Hemingway.

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It's all being quickly consumed by unique communities of microbes.

"We don't yet know exactly which bacteria are doing this -- that would require genomics, metagenomics, and other microbiological tools that we didn't use in this study. But that's the next step for this research," said Valier Galy, a marine geochemist with the Woods Hole Oceanographic Institute.

Across short timescales, the amount of CO2 being released into the atmosphere isn't significant enough to effect global climate change, but understanding the erosion process is essential to understating the planet's many carbon cycles.

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In future studies, researchers hope to determine how the erosion process helped stabilize CO2 over long periods of time.

"Throughout our Earth's history, CO2 has wobbled over time, but has remained in that stable zone," said Hemingway. "This is just an update of the mechanism of geological processes that allows that to happen."

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