When we think of the earth beneath our feet, we generally think we’re on solid ground. But soil is anything but solid. With roughly six billion organisms in a single tablespoon, healthy soil is a vast, dynamic, and hidden microcosmos. In the words of journalist Kristin Ohlson, “We’re standing on something that’s more like a coral reef.”
Ohlson recently spoke at a panel discussion hosted by CUESA called “The Soil Will Save Us.” In researching her book by the same name, she interviewed scientists and farmers who are putting those soil communities to work. She came away with awe and hope for soil’s complexity and its immense potential to heal the planet.
Human activities like burning fossil fuels have led to global warming by increasing the concentration of greenhouse gases, most notably carbon dioxide, in the atmosphere. Reversing climate change is not just a matter of decreasing our dependence on fossil fuels, but also reducing the excess CO2 that is currently in the atmosphere.
That’s where soil comes in.
Healthy soil captures and stores atmospheric carbon. Through photosynthesis, plants convert CO2 into the food they need to grow. About 40% of that carbon gets deposited into the soil through the plants, where it feeds microorganisms like bacteria, fungi, protozoa, and nematodes. Those creatures, in return, give mineral nutrients to the plants, providing a natural fertilizer.
Ohlson calls this process the “ancient partnership between soil microorganisms and plants,” and it is an important part of the carbon cycle. Modern industrial agricultural practices such as monoculture planting, use of chemical fertilizers and pesticides, and tilling have disrupted this natural cycle, decreasing soil health and diversity and releasing harmful CO2 into the atmosphere.
“The only way to bring [CO2] down is through plants,” said Ohlson. “That’s the great hope that we have not only for healing our climate, but for also healing all these other environmental ills we have, whether it’s erosion or drought or floods or poor water and air quality.”
Farming for the Climate
As scientists warn about the urgency of climate change and California faces its most severe drought on record, some farmers and environmentalists are looking not to the air, but to the earth. “A third of the excess carbon dioxide in atmosphere today is a direct function of how we have managed landscapes for the last 10,000 years,” said Jeff Creque, co-founder of the Marin Carbon Project and director of the Carbon Cycle Institute.
And Creque sees responsible soil stewardship as the solution. In 2007, he and his colleagues asked the question, “Can management enhance carbon sequestration in our rangeland soils?” Working with ranches and agricultural organizations in Marin County, they spread half an inch of compost on several sites and quickly saw an increase in plant production, soil moisture, and soil carbon.
The Marin Carbon Project’s goal is to implement “carbon farming” practices (like compost application, cover crops, and no-till cultivation) on ranches throughout California. He estimates that if compost were applied to 5% of California’s rangelands, it would offset of 32 to 36 million metric tons of carbon dioxide.
As the planet warms and water becomes scarcer, the implications of carbon farming are huge. In addition to mitigating and possibly even reversing climate change, these practices can also lessen the impacts of the drought. “We’re looking at the potential to hold more water in our soils than in all of our state’s reservoirs combined,” Creque said.
Healthy Soil, Healthy Farms
Carbon farming techniques increase microbial life in the soil, which may bring additional benefits for farmers, such as increased fertility and reduced need for chemical fertilizers and pesticides.
Since he started making his own compost and letting his cover crops grow wild three years ago, Farmer Al Courchesne has witnessed a transformation at Frog Hollow Farm, his 145-acre organic fruit orchard in Brentwood. “We’ve had the best apricot crop ever,” he said. His trees have been more resistant to diseases such as brown rot, which have wiped out his apricots in past years.
To make compost, the farm uses fruit that would otherwise go to waste, wood chips from the orchards, shredded cardboard boxes, spent coffee grounds, and waste collected from restaurants. One big culprit in global warming is the food waste that rots in landfills, which produces another powerful greenhouse gas: methane. Composting prevents this methane production by diverting organic matter from the waste stream and instead recycling it into the soil, where it feeds soil microbes and serves as a natural and potent fertilizer.
Heroes of the Underground
Implementing carbon farming practices on a large scale would require sweeping changes in agricultural policy, which will not come easily. “There’s fear among the more conservative agriculture sector that they’re going to be regulated as a greenhouse gas emitter,” said Creque. “The opportunity to be recognized for greenhouse gas mitigation and reversal of climate change is missing.”
Ohlson sees hope in a new program launched by the National Resources Conservation Service in Oregon that compensates farmers for transitioning to no-till practices and planting cover crops.
Citizens can do their part by buying food from soil-conscious farmers, advocating for policies that support responsible land stewardship, and gardening with climate-friendly practices.
Creque emphasized composting as an easy and important action that many of us can take, particularly in San Francisco, where there is municipal compost collection. “We have upwards of 30 million tons of organics being disposed of in California in landfills and anaerobic manure lagoons on confined feeding operations [industrial animal farms],” he noted. “It is producing high-potency methane that would be hugely beneficial to get out of the waste stream.”
Reversing the effects of climate change will take all hands on deck, but Ohlson is optimistic, as long as we give back to the soil that gives so much to us. “I think all of us can be heroes of the underground,” she said in closing. “We can get a grip on what is happening to our landscapes and climate, and reverse a lot of the damage that’s been done.”
Carbon cycle art from Intergovernmental Panel on Climate Change (IPCC).
CUESA (Center for Urban Education about Sustainable Agriculture) is dedicated to cultivating a sustainable food system through the operation of farmers markets and educational programs. Learn More »