When it’s healthy, soil is incredibly effective at storing carbon, Berhe said on the stage at TED in Vancouver. Soil stores around 3,000 billion metric tons of carbon, which is double the amount stored in vegetation and in the atmosphere, combined. The ability of natural ecosystems like soil to capture and sequester carbon is essentially bailing us out of experiencing the effects of excessive amounts of CO2 that human activities produce. Around half of the 9.4 billion metric tons of CO2 released into the atmosphere every year are captured in soil, plants, and the ocean, and soil is doing the bulk of that heavy lifting.
But “the ability of these natural ecosystems to take up carbon dioxide from the atmosphere and sequester it is being compromised, as they’re experiencing serious degradation because of human actions,” Berhe says.
Soil, Berhe says, is suffering as a result of human action and the climate shifts it’s causing. Around half of the world’s soil is degraded, and everything from excessive use of chemicals in farming, single-crop agricultural practices, deforestation, and drought are to blame.
Degraded soil has a diminished capability to support plant productivity, which compromises our ability to grow food and vegetation, which further sequesters carbon. And when soil degrades, the rich minerals to which carbon binds break down, and end up leaking back into the atmosphere. That release of additional carbon will only further contribute to global warming. Furthermore, Arctic permafrost has been especially effective at trapping carbon in the soil, but as the permafrost melts, that carbon—which accounts for around one-third of all carbon trapped in soil—is getting out. “This could start a self-reinforcing feedback loop that could go on and on, dramatically changing our climate future,” Berhe says.
But just as human activity is causing the conditions that are causing soil to erode and lose its carbon-storage capabilities, we can advance practices to reverse that damage. Climate-smart land management practices, Berhe says, which are often referred to as “regenerative agriculture,” will be crucial for restoring soil health. The agricultural industry needs to prioritize planting perennial plants, whose deep roots are especially effective at storing carbon long-term, as well as reducing the use of chemicals and excessive grazing. Greater crop diversity, too, will help return carbon-binding minerals to the soil, and integrating compost and even human and animal waste to soil will support its health and carbon-storing ability.
Berhe still believes that we can save the soil and increase its carbon-storing potential “as long as we stop treating it like dirt.”
Healthy, fertile soils are rich in organic matter built of carbon that living plants pulled out of the atmosphere through photosynthesis. Carbon-rich organic matter helps fuel the soil organisms that recycle and release mineral elements that plants take back up as nutrients.
But soils release carbon too. And the frequent tillage and heavy fertilizer use that underpin modern conventional agriculture have accelerated degradation of soil organic matter, sending more carbon skyward – a lot, it turns out.
Climate change is roiling the African continent.
The new IPCC report concludes that globally, cropland soils have lost 20-60% of their original organic carbon content. North American farmland has lost about half of its natural endowment of soil carbon. On top of those losses, modern agriculture consumes a lot of fossil fuels to pull plows and manufacture the synthetic nitrogen fertilizers that farmers rely on to coax large harvests from degraded soils.
Land management choices also affect the amount of carbon stored in trees, plants and soil. The new IPCC report estimates that serious changes in forestry and agriculture to curtail deforestation and improve soil management could reduce global emissions by 5% to 20%. While this won’t solve the climate problem, it would represent a significant down payment on a global solution.
According to a 2018 U.N. report that reviewed global land degradation, the economic benefits of land restoration average 10 times the costs. Rebuilding fertile soil is also one of the most promising ways to address hunger and malnutrition in Africa, where the costs of failing to combat land degradation are typically three times the cost of addressing the problem.
Restoring soil health would help mitigate the effects of climate change. Increasing the amount of organic matter in soil enhances its ability to hold water. And improving soil structure would let more rainfall sink into the ground, where it can better sustain crops – especially during drought-stressed years – and help reduce flooding downstream. In addition to benefiting the climate, less fertilizer use will reduce off-farm water pollution.
Regenerative practices that focus on soil building bring other benefits too. For example, one 2006 study surveyed low-input, resource-conserving agricultural practices in 286 development projects across Latin America, Africa and Asia that employed cover crops for nitrogen fixation and erosion control and integrated livestock back into farming systems. It found that for a wide variety of systems and crops, yields increased an average of almost 80%. Results like these indicate that investing in soil-building practices would help feed a warming world.
When President John F. Kennedy called for a national effort to go to the Moon, the U.S. managed to do the unthinkable in under a decade. I believe it’s time now for a global “soilshot” to heal the land. Rebuilding healthy fertile soil on the world’s agricultural lands would require fundamental changes to agriculture, and a new agricultural philosophy. But consider who stands to lose from such a shift: corporate interests that profit from modern agrochemical-intensive farming and factory-farm livestock production. Who stands to gain? Everyone else.
