The World Resources Institute questions claims that the farming practice is able to sequester large amounts of carbon
Regenerative agriculture can do many things.
It can improve soil health. It can make farming more resilient to droughts, floods and weather extremes. It may make land more productive.
But it cannot solve climate change, say experts with the World Resources Institute (WRI).
“There’s obviously very high interest, right now, in soil carbon sequestration and regenerative ag practices to help mitigate climate change. These practices are good for improving soil health, while building resilience to climate change,” said Rich Waite, senior research associate with the WRI food program, during a June 10 webinar.
“Soils have physical capacity to store more carbon, but… we think the realistic ability to sequester additional carbon in working agricultural soils, is limited in scale.”
Waite and his WRI colleagues, along with a soil expert from Rothamsted Research, an agricultural science centre in England, spoke and answered questions about regenerative ag for about 60 minutes.
Regenerative ag includes practices like zero tillage, diverse crop rotations, cover crops and integrating livestock into farm operations to improve soil health and productivity.
It is gaining traction in parts of Western Canada as more producers seek ways to reduce crop input costs and improve profitability.
Some proponents have argued it can also help with climate change. If regenerative agriculture increases the amount of carbon stored in soil, then less carbon is in the atmosphere.
A French initiative, called 4 per 1,000, argues that a 0.4 percent increase in soil carbon stocks annually would “significantly reduce the CO2 concentration in the atmosphere related to human activities.”
That argument has merit because there is a massive amount of carbon in the world’s soils, the WRI scientists said during the webinar.
“It’s been estimated that the organic matter in the world’s soils, to a depth of one metre, can take about 1,500 gigatonnes of carbon,” said David Powlson, a soil scientist with Rothamsted Research. “That’s about twice the amount of carbon that’s in the CO2 in the atmosphere. And about three times that is in vegetation.”
Increasing the amount of carbon in farmland soil every year by a fraction would make a difference.
In reality, getting more carbon into agricultural soils and making it stay in the soil is not easy.
“We consider large estimates of climate change mitigation potential for agricultural soil carbon to be unrealistic,” the WRI says on its website. “Many published claims of massive potential do not address (the) scientific and practical challenges.”
One of the practical challenges is zero tillage.
It does reduce soil erosion and can store more carbon, in the top layer of soil, but millions of acres in Western Canada were converted to reduced tillage 25 years ago. The opportunity for additional gains every year may be limited.
“In South America, zero till is (also) very, very widely practised,” Powlson said.
The WRI scientists also discussed integrating livestock into crop production, where the same land is used for crops and pasture. Pasture grasses do grow deeper roots and can sequester more carbon in the soil. But taking cropland out of production, so livestock can graze, comes with a cost.
To produce the same amount of wheat, canola or barley, some pastureland may have to be converted to cropland, the WRI scientists said. So you’re borrowing from Peter to pay Paul.
And switching between pasture and crops requires cultivation.
“Probably, you’ll have less carbon benefit from the grass because you’re plowing it up, periodically,” said Tim Searchinger, a senior fellow with WRI and a research scholar at Princeton University.
Cover crops may offer the most potential for storing additional carbon in the soil.
They are grown on only about four percent of U.S. farmland and increasing that to 85 percent could sequester 100 million tons of CO2 per year, WRI said, citing a 2018 study.
“Such an unprecedented achievement would offset about 18 percent of U.S. agricultural production emissions,” the WRI said.
“Cover crops should be actively promoted given their potential to improve soil health, reduce nitrogen pollution and create climate benefits, but their realistic potential for soil carbon gains is uncertain at this time.”
Instead of focusing on soil and sequestering carbon in soil, policy makers should look other ways to reduce agricultural emissions, Waite said.
That includes several possibilities:
- eating less meat
- reducing crop and food waste
- improving crop yields and livestock production on existing lands
- managing nitrogen
- avoiding deforestation
- stopping draining wetlands and peatlands, which store a massive amount of carbon
In other words, the natural soils that store carbon should not be converted to farmland, which would release a huge amount of CO2 into the atmosphere, Powlson said.
He added that regenerative ag has definite benefits, like improving soil health and reducing the need for pesticides. But storing carbon in the soil, through regenerative ag, is not a replacement for reducing emissions from agriculture.
Carbon sequestration can make a slight difference with climate change. Right now, its promise is over-hyped.
“It should not be dismissed,” Powlson said. “Or exaggerated, which I think it often is.”