Eroding mountains could release, not trap, greenhouse gases

0
110
Microbial processes in Taiwan’s Central Mountain Range may point to a new source of atmospheric carbon. WENILIOU/SHUTTERSTOCK.COM

Eroding mountains could release, not trap, greenhouse gases

The hills are hiding a carbon cache. For decades, scientists believed that the erosion of mountains caused carbon dioxide (CO2) in the atmosphere to drop, as silicate rocks newly exposed to rainwater would “weather,” taking up carbon in carbonate minerals that would sluice down rivers and be sequestered on the sea floor.

But a new line of research, published this week in Science, is complicating that picture. A team of scientists has found that, thanks to opportunistic microbes, some mountain ranges may be sources, not sinks, of carbon. The discovery won’t mean much for climate change: The process occurs over millions of years, and the amounts involved are small compared with human-driven emissions. But it is a new type of feedback mechanism for Earth, one that could have helped the planet maintain its carbon thermostat prior to human interference. “This is part of the carbon cycle that people don’t think about—or don’t really know exists,” says Jordon Hemingway, a geochemist at Harvard University and the study’s lead author.

Hemingway’s coauthors worked in the Central Mountain Range of Taiwan, one of the fastest rising—and eroding—belts in the world. It’s a dramatic landscape formed by the collision of two tectonic plates, with sheer peaks plummeting into the Pacific Ocean. About 0.5% to 1% of the rocks in the range contain carbon, the organic remains of fossilized life buried in sedimentary rocks like shale. This locked-up “petrogenic” carbon comes at the end of a long journey. It started when the corpses of microbes and algae fell to the sea floor and got sucked into Earth’s mantle by diving tectonic plates. There, the carbon was crushed and cooked until it was eventually returned to the surface by the clashing plates.