Jon Foley, executive director of Project Drawdown, agrees, and says assertions to this effect make it more difficult to set realistic expectations for climate mitigation strategies. “Regenerative agriculture is a powerful drawdown, both to reduce emissions and add new carbon sinks,” he says. But “preposterous claims that are easily debunked only undermine the message that regenerative agriculture is one of the few areas that can [potentially] solve around 10 percent of climate change.” If so, it would be on par with solar or wind energy, says Foley. “No one thing can possibly fix climate change.”
White papers, unlike scientific publications, are not peer-reviewed examinations of new data. “This white paper is not based on a study in which we transform or shift every single [farm] field around the world,” says Rui, which he notes is impossible.
But just how rooted their perspective is in existing facts is in question. And the experts we spoke to had several criticisms of the white paper. First, experts claim that the Institute ignores more careful analyses, like Lal’s and others, which suggest that regenerative agriculture can offset at most 10-15 percent of emissions. “When I tell people that we can offset up to 15 percent [using soil as a carbon sink], they tell me I’m overly optimistic,” says Lal.
And, instead of rigorously doing an analysis with real-world data, it appears that the white paper authors simply picked a couple of hand-selected sites and multiplied that by the entire land area on Earth, says Foley.
To that end, the carbon sequestration potential of different soils—and the fact that soil doesn’t store carbon permanently, but can hit a limit and even be reversed—are not taken into account. According to a recent peer-reviewed study of soil carbon storage in global ecosystems published in the Proceedings of the National Academy of Sciences (PNAS), for example, the fraction of carbon that is transferred belowground—where it can be stored longer-term—decreases with precipitation and varies significantly between croplands, savannas, and forest.
While degraded soils can accumulate carbon quickly, says Osvaldo Sala, a coauthor of the PNAS study and a soil scientist at Arizona State University, healthy ecosystems are full of invertebrates and microorganisms that recycle nutrients and consume organic matter, which emits carbon dioxide. “There’s a natural limit on the amount of carbon that a healthy ecosystem can hold,” says Sala.
Critics also say the Rodale white paper is not based on research that conducts a full life cycle analysis of net carbon accrued. Where does the carbon to build the soil organic matter come from? If from food waste or manure, the transportation to apply it should be subtracted from the amount of net carbon sequestered, says William Schlesinger, retired president of the Cary Institute of Ecosystem Studies, a not-for-profit research organization in Millbrook, New York.
And, Schlesinger adds, soil doesn’t just store carbon. Other nutrients, including nitrogen and phosphorous are found in humus, the stable form of stored organic matter. “If we wanted to sequester all of fossil fuel emissions in the atmosphere in soil organic matter, it would take four times the nitrogen fertilizer already used today,” he calculates. And those applications would certainly come with global warming nitrous oxide emissions and nutrient runoff.
“Regenerative agriculture is like apple pie: It’s a warm and friendly concept that no one can be against.”