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A surprising ally in the battle against climate change: dirt

By changing farming practices, an extra 9 billion tons of greenhouse gases could be locked away in the soil, according to an international team of scientists.

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    A farmer harvests broccoli in the town of al-Ansariyeh south of Sidon, Lebanon in March.
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Earth’s soils represent a potential storehouse for billions of tons of greenhouse gases, a vital addition to our arsenal for combating climate change, according to new research.

The international group of scientists, whose findings are published Wednesday in the journal Nature, argue that carbon sequestration in soil has been under-appreciated and under-utilized, but has vast potential.

Their goal was therefore to synthesize a wealth of knowledge and expertise and bring it to the attention of both the public and policy-makers.

"The single most important take-away from this work is that how we manage our landscapes and soils can make a difference in managing greenhouse gases and climate change," says first author Keith Paustian of Colorado State University in Fort Collins, Colo., in a telephone interview with The Christian Science Monitor.

"And if we do manage soils in an effort to reduce greenhouse gases, there is also a huge side benefit in terms of healthier soils, and ecosystem services such as less runoff, less soil erosion, and less nitrate leaching that causes problems in the Gulf of Mexico, Chesapeake Bay, and lots of waterways."

Agriculture is directly responsible for 10 to 14 percent of global greenhouse gas emissions, plus an additional 12 to 15 percent from land conversion (mostly deforestation) to facilitate agriculture.

So, while fossil fuels are responsible for the lion's share of greenhouse gas emissions, the role of land use shouldn't be overlooked, say scientists.

In fact, agricultural soils can be made to capture even more greenhouse gases than they emit, making them "net mitigating," explains co-author Phil Robertson of Michigan State University in East Lansing, Mich., in a Monitor interview. 

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"Three important game-changing practices are available today: no-till, cover crops, and advanced nitrogen fertilizer management," says Dr. Robertson in a follow-up e-mail.

In no-till cultivation, crops are grown without plowing. Winter cover crops capture carbon in months when the main crop is absent. And nitrogen fertilizer management refers to a system of applying just enough fertilizer to meet plants' need, instead of spraying indiscriminately.

Of course, the single best way to turn land into a carbon sink is to turn it into a forest, but pragmatism dictates that the more realistic path lies in adapting agricultural practices.

"We know from research in the US that the technology's available, but farmers are rational human beings and their first priority is paying bills, not reducing greenhouse gases," Robertson says. "Farmers don’t change their crop system practices because it would generally cost more in terms of labor, equipment, and soil management efforts."

His solution? Incentives. Pay farmers to adopt different agricultural practices.

"We know it works because we've had conservation payments in place for decades," says Robertson. "And because of the large scale of agriculture, a small change at the field level will have a huge impact on the continental level."

Policymakers have already begun implementing strategies in line with these recommendations, as in the US Department of Agriculture’s "building blocks" program "to help farmers, ranchers, and forest landowners respond to climate change."

Targeted legislation would make a bigger difference, argues Robertson, but that would be a difficult road to navigate in the current political climate. But co-author Pete Smith of the University of Aberdeen, Scotland, sees reason for hope.

Carbon-friendly land use practices are "something we've known about for some time, and there’s no better moment than now for action," says Dr. Smith in a telephone interview with the Monitor. "Last year was the United Nations' international year of soils, which coincided with the Paris climate agreement in December. This gives us the policy drive for making this a reality."

 
 
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