Peak Soil Has a Simple Fix, But Will We Manage It?

At the Carbon Farming conference in Australia earlier this month, speakers pointed to a problem that has worried environmentalists for about a decade: peak soil.

China is losing soil 57 times faster than nature can replace it, according to John Crawford, a professor at the University of Sydney’s Institute of Soil Sciences. In the United States, conservation practices have helped reduce soil loss, but top soil is still being eroded 10 times faster than it can be replaced, according to the National Academy of Sciences.

This is a concern, not only because it limits the amount of food-producing land, but also because soil and the crops that grow in it can help sequester carbon, so the more of it we lose, the more carbon we leave out in the atmosphere.

The cause of all this soil loss? Ostensibly wind, rain and other natural forces, but industrial agriculture is also partly to blame, particularly the practices of monoculture, overgrazing, the use of chemical fertilizers and pesticides and a lack of cover crops.

When there is no crop residue (leaves, stalks, etc.) or cover crop on fields, the soil is left unprotected and can easily be lifted away by winds and rain. Meanwhile, the application of chemicals to the soil break down its structure over time, causing further erosion.

“Industrialized high-input agriculture can increase [food] production, but it can also contribute to global warming, loss of biodiversity, loss of soil fertility and over-consumption of water,” Lars Peder Brekk, minister of food and agriculture for Norway, told the World Summit on Food Security this week in Rome.

“Strategies must therefore be based on sustainable production methods and recognize the role of small-scale agriculture.”

The Food and Agriculture Organization of the United Nations (FAO) has been warning for nearly a decade that 140 million hectares of high quality soil, mostly in Africa and Asia, would be degraded by 2010 unless better methods of land management were adopted. In 2006, researchers at Cornell University reported that soil around the world was being
depleted at a rate that was 10 to 40 times faster than the rate it was being replenished. Current statistics from Worldometers puts the total amount of arable land lost this year alone to erosion at over 5 million hectares and growing.

When the Cornell study was published, co-author David Pimentel called soil erosion second only to population growth as the biggest environmental problem the world faces and lamented the fact that the problem was being ignored, particularly when the solution was relatively easy.

"Controlling soil erosion is really quite simple,” Pimentel said then. “The soil can be protected with cover crops when the land is not being used to grow crops."

Now, experts are promoting such practices not just to save land for more food production, but also to help sequester carbon.

Rattan Lal, director of the Carbon Management and Sequestration Center at Ohio State University, writes in a briefing paper for the Copenhagen negotiations that soil could sequester 3 billion tons of CO2 per year for the next 50 years, equivalent to a reduction of 50 parts per million of atmospheric CO2 by 2100.

The Rodale Institute’s 23-year study comparing organic and conventional farming found that organic grain production systems increase soil carbon 15 to 28 percent and that soil nitrogen in the organic systems increased 8 to 15 percent.

“Practical organic agriculture, if practiced on the planet’s 3.5 billion tillable acres, could sequester nearly 40 percent of current CO2 emissions,” Rodale Institute CEO Tim LaSalle wrote.

So why haven’t we heard more about peak soil and carbon farming?

In part, LaSalle says, because soil could sequester so much carbon so easily that promoting such a thing could make people drop the idea of cutting emissions.