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December 5th, 2017 / Scientific American

Soil management offers huge potential for keeping carbon emissions in the ground

Soil management doesn’t sound snazzy, but scientists say it offers huge potential for keeping carbon emissions in the ground—and out of the atmosphere.

A paper published this week in the journal Scientific Reports estimates that improved land-use practices could increase the amount of carbon stored in the top layer of soils worldwide by between 0.9 and 1.85 billion metric tons each year.

At the high end, that’s about as much carbon as is emitted by the transportation sector annually, the researchers note.

rotecting and expanding the world’s carbon sinks—including the ocean, the soil, global forests and other types of vegetation, all of which naturally store away carbon that would otherwise go into the atmosphere—is increasingly regarded by scientists as a major climate change mitigation tool. Worldwide, scientists estimate that the planet’s soil alone contains about 2.5 trillion tons of carbon in its top 3-foot layer. That’s about 250 times more carbon than is emitted into the atmosphere by humans each year.

Human activities, such as converting land for agriculture, have the potential to seriously disturb the soil and release large amounts of carbon into the atmosphere. In fact, one recent study suggested that agriculture-related changes of land use over the last 12,000 years of human history have released about 133 billion tons of carbon into the air, equivalent to about 13 years of present-day fossil fuel emissions. And the majority of those soil-related emissions have likely occurred in the last few centuries alone.

But scientists now increasingly suggest that improving soil health, through practices such as rotating crops or composting, can increase its carbon-storing potential. This week’s paper uses information from global soil and land-cover databases to investigate how much more carbon might be sequestered in locations around the world under improved land management practices, building on previous research published in 2014.

Storage potential differs region by region, the researchers note. North America has the highest potential for total amount of carbon storage over all the land available, although parts of South Asia and North Africa have the greatest potential for storage on a per-hectare basis. Read more