Carbon emissions from land use changes and deforestation will have to hit zero in the next three years to hit the goals set out in the Paris agreement, soil scientists Keith Shepherd and Rolf Sommer argue in a post yesterday to mark Earth Overshoot Day.
“The top metre of soils around the world contains about three times as much carbon as in our entire atmosphere,” they write on Carbon Brief. “This means that soils can be a double-edged sword for tackling climate change.” While clearing land for farming and other uses releases carbon to the atmosphere, “managing soils carefully and restoring their fertility means they can take up more carbon, helping to mitigate our CO2 emissions and thereby limiting climate change.”
They note that restoration efforts on the 16 million square kilometres of suitable farmland around the world would meet 25 to 50% of the target in the 4 Pour Mille (four per thousand, or 0.4%) initiative introduced by France in conjunction with the 2015 UN climate conference in Paris—for a saving of 0.9 to 1.85 gigatonnes of carbon per year, or about six to 13% of all emissions from human activity.
Shepherd and Sommer cite soil and water conservation, sustainable land management, and improved soil data as three relatively simple, affordable steps to cut emissions from soils in Africa, restore landscapes, and perhaps turn those lands into sinks that store carbon, rather than releasing it.
“Overall, the annual global cost of land degradation is estimated at around US$300 billion,” they write. “Yet the cost of taking action against land degradation is much lower than the cost of inaction, and the returns are high. For example, on average, a $1 investment into restoration of degraded land returns $5. This means it makes both environmental and economic sense.”
Meanwhile, a new carbon farming effort in California is exploring similar strategies to the ones Shepherd and Sommer are recommending for Africa. Under the Healthy Soils Initiative, the state food and agriculture department offers farmers and ranchers up to $50,000 in grants to improve soil quality and plant growth through regenerative agriculture.
“The statewide soil program is the first of its kind in the United States, and the goal is to store carbon while treating the soil beneath farmers’ and ranchers’ feet as part of a living system,” News Deeply reports. “Advocates for adding compost to farmland and grassland believe dirt, much like humans, requires good food to remain healthy and productive. Good dirt, in turn, produces abundant plants with a healthy appetite for carbon.”
“Humanity can benefit,” said rancher Kevin Muno. “People in the city like clean air and water in their reservoirs. If we manage the landscape correctly, we can have those things.” The program encourages shifts in farm practice like free-range livestock, composting, and better care of grasslands, all aimed at turning soil into a carbon sink that retains more water and provides more of the organic matter on which plant growth depends.
The work is based on a study by scientists at the University of California, Berkeley and the Marin Carbon Project, which found that a single, half-inch application of compost increased grasslands’ carbon retention by a ton per hectare.
“While measuring the potential for carbon sequestration on grasslands was the primary focus of the study, there were multiple benefits. The findings showed spreading compost also boosted plant growth by 40 to 70%. In addition, each hectare of land absorbed up to 6,868 gallons of water in the topsoil, allowing the grassland to remain lush and vibrant for extended periods.”