Although previous experiments have shown that compost increases soil carbon, Silver is among the first to examine whether real-world ranchers can use it effectively to enrich the soil on their rangeland. She has already found a large increase in soil carbon two years after a single application of compost, probably due to enhanced vegetation growth. On the basis of her results, Silver projects that 28 million acres of grazing land in California could absorb 42 million tons of carbon dioxide—nearly 40 percent of what the state’s electrical power plants produce in a year. To accomplish that, each acre of land must absorb just 1.5 additional tons of carbon dioxide. “Given what we’ve seen in our experiments,” Silver says, “one and a half tons is doable.”
In Australia, Christine Jones, soil ecologist emerita of the New South Wales Department of Land and Water Conservation, is testing another promising soil-
enrichment strategy, one that relies on perennial grasses. Since carbon sequestration stops in the absence of living plants, Jones and 12 ranchers in Western Australia are working to build up soil carbon by cultivating grasses that stay green year-round. Like composting, the approach has already been proved experimentally; Jones now hopes to show that it can be applied on working ranches and that the resulting carbon capture can be accurately measured. Over the course of four years, she has charted the carbon content of the grasslands, and when the first phase of the project concludes this August, philanthropist Rhonda
Willson will pay the ranchers for every additional ton of carbon tucked away in their soils.
“The changes we’ve registered over the past few years will surprise the world,” Jones says.
Silver and Jones hope that projects such as theirs will demonstrate the role that farmers,
ranchers, and other land managers can play in mitigating the effects of heat-trapping greenhouse gases. Lal says that the greatest opportunities lie in the world’s most depleted and eroded soils, in sub-Saharan Africa, south and central Asia, and Central America. Success there will rely on providing farmers the tools and knowledge to improve their land, as well as financial compensation for their carbon enrichment of the soil.
The same is true in wealthier societies like the United States, where most farming operations chase productivity through large applications of fertilizer. Changing long-standing habits will require a system that rewards land
managers not just for the corn or beef they produce, but also for the carbon they can build into their property. “Farmers should get compensated for protecting the ecosystem,” Lal says. “This is something worth paying for.”
An approach that aims to protect natural resources such as soil through techniques including crop diversity and rotation.
A reservoir that can hold carbon and prevent it from escaping into the atmosphere. Proper management could turn agricultural soils into a powerful sink.
Marin Carbon Project A joint effort by scientists and ranchers in California to study rangeland’s potential to soak up carbon.
Fertilizer made of decaying organic matter. By boosting plant growth, compost helps to increase soil carbon storage.
According to an ongoing study in Australia, planting ranch lands with grasses that remain alive year-round also increases the amount of carbon trapped in the land.