When it comes to reducing the impact of climate change, humanity appears caught between a rock and a hard place.

But, in this case, the rock may offer a surprisingly softer landing.

The rocky surface of our planet’s geology may provide a buffered bumper to absorb excess carbon – that is, if society wants to protect Earth, according to a new paper co-authored by Benjamin Houlton, Cornell’s Ronald P. Lynch Dean of the College of Agriculture and Life Sciences, and professor of ecology and evolutionary biology.

The study, led by the University of California at Davis, Northern Arizona University and Cornell, published Oct. 4 in the journal Global Biogeochemical Cycles.

“Excess carbon is already harming people, economies and our planet,” said Houlton, the paper’s senior author “But we’ve been enjoying a free subsidy provided by Earth – a large carbon sink on land and in the ocean – and, as a society we’re not paying for the carbon-sink service explicitly. But where is this sink and how long will it last?”

The new research demonstrates that something as simple as rock-weathering reactions – slowly releasing nitrogen once bound up in rocks, which nature has been doing long before humans – slowly deliver natural fertilizers around the world, allowing large areas of terrestrial habitat to take up carbon dioxide.

Since the start of the Industrial Revolution, humanity has been pouring carbon dioxide into the atmosphere. However, land and its vegetation has been naturally drawing down nearly a quarter of it. It was only in the late 1990s that scientists discovered this terrestrial carbon sink. With another quarter of the carbon dioxide going into the oceans, the remaining half of the carbon dioxide remains in the atmosphere contributing to climate change.

“We’re facing incredible threats from climate change and unless we find pathways to store and sequester carbon, it will get worse,” Houlton said.

Through the rest of the century, background nitrogen inputs from rock weathering and biological fixation can contribute two to five times more to terrestrial carbon uptake than nitrogen pollution primarily from agricultural and industrial activities, said the scientists, looking at a business-as-usual scenario.

“Previously, we had believed that this terrestrial carbon sink was more vulnerable,” said lead author Pawlok Dass, a postdoctoral researcher at Northern Arizona University, formerly in Houlton’s laboratory at the University of California, Davis, where Houlton conducted the research before coming to Cornell. “Now we're suggesting that because of the previously undiscovered slow-release nitrogen, the terrestrial carbon sink will continue to be robust.”

Still, society should not lower its guard, as fossil fuel use tends to add excess nitrogen to the atmosphere, which instead of acting as a fertilizer, bypasses terrestrial carbon cycles, which in turn, pollutes downstream water bodies. Abating such excess nitrogen pollution can boost human health, environment and the economy, Dass said, without jeopardizing the natural, terrestrial carbon sinks.

 Dass explained that to preserve carbon sinks, we need to conserve places where rock nitrogen weathering or biological nitrogen fixation is strong – such as the biologically diverse tropical forests, mountainous regions and the rapidly changing boreal zone (the entire stretch of forests stretching from Alaska to Canada to Siberia, for example).

“Our work suggests that the conservation of these ecosystems, which have built-in capacity to absorb carbon dioxide,” Houlton said, “is going to be vital to making sure that we don’t lose out on Earth’s terrestrial carbon sink service in the future.”

In addition to Dass and Houlton on the research, “Bedrock Weathering Controls on Terrestrial Carbon-Nitrogen-Climate Interactions,” the other researchers include Yingping Wang, of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Oceans and Atmosphere, Australia; David Warlind, Lund University, Sweden; and Scott Morford, University of Montana, Missoula.

Funding for this research was provided by the NSF.