Scientists say that removing carbon from the atmosphere may be critical to slowing the effects of climate change. Research is underway on methods of using technology to capture carbon and then use it or permanently store it so that it doesn't re-enter the atmosphere. There are also natural methods of carbon sequestration. Soil, for example, can sequester large amounts of carbon. Improving soil health can enable it to store more and may help fight climate change.
How soil sequesters carbon
The earth's soil stores around 2,500 gigatons of carbon and captures 25 percent of global fossil fuel emissions. Here's how it works. Plants absorb carbon dioxide from the atmosphere and convert it into carbon, which they use to grow. The plant sends excess carbon down into the soil where microbes and fungi use it as food. This carbon that plants send into the soil is referred to as soil organic carbon. It's the main ingredient in soil organic matter, it provides structure to the soil and enables it to store more water.
This carbon might remain in the soil for thousands of years. It could be released back into the atmosphere. Human activities such as farming, mining and land development can disturb soil and make it less healthy, increasing the amount of carbon that gets released from the soil back into the atmosphere.
Being more careful about how we manage soil health, though, can increase the amount of carbon that stays in the soil. Keeping it in the ground helps reduce the greenhouse gas effect that's causing climate change. Estimates vary for how much carbon the soil can capture and how fast, but a 2017 study published in the journal Nature estimated that the world's croplands could store 1.85 gigatons more carbon each year if soil management improved.
- Soil management methods There are many ways to improve soil health. Using these soil management practices could help slow climate change and help farmers grow more food, promote biodiversity and make soil less susceptible to problems such as erosion, nutrient loss, and desertification. Cover Crops or Leaving Plant Residue Planting cover crops in between annual harvests of cash crops can help put more carbon in the soil as well as protect it from erosion and decrease nutrient loss. Cover crops are typically non-cash crops such as clover. Leaving plant residue on the ground as a cover can have a similar effect. Reduced Tillage Tilling and plowing disturb the soil and cause carbon to be released into the atmosphere. Reducing or even eliminating tillage and plowing keeps carbon in the ground and improves soil health. It also increases the number of nutrients in the soil and helps prevent erosion. Bioremediation When a piece of land becomes highly contaminated with pollutants, we can use bioremediation to help restore it. Bioremediation involves using microbes to neutralize or remove pollutants. These pollutants may include gasoline and diesel fuel from petroleum stations, wood preservatives from lumber processing yards and fertilizers and insecticides from farms.
- Crop Rotation and Use of Diverse Crops Rotating crops and planting a diverse set of crops on farmland also improves soil health. It adds more varied biomass and nutrients to the soil, some of which may help add more carbon to the soil. This leads to healthier soil and healthier crops.
- Rotational grazing Overgrazing is a problem in which herds graze in one area for too long, depleting it of plant life. Without plant life, there is no opportunity for more carbon to enter the soil and the risk of erosion rises. Rotational grazing involves moving herds from field to field in a way that allows plants to regrow. This prevents overgrazing and also spreads carbon in the form of manure.
- Manure and Compost Adding manure or compost to soil promotes the formation of carbon and increases the soil's productivity. According to one study from the University of California at Berkely, adding compost to 25 percent of grasslands in California would increase sequestered carbon by about 21 million metric tons.
- Planting More Perennial Crops Perennial crops live for multiple growing seasons, while annual crops only live for one. Planting more perennials can increase the amount of carbon stored in the soil because their roots can reach deeper into the ground due to their longer lifespans. These more extensive root systems also prove the benefit of reducing erosion.
Healthy soil offers many benefits including increased productivity and reduced erosion. One of the most important benefits is its ability to sequester more carbon, reducing the effects of climate change. While improving soil health won't solve climate change all by itself, it may be a key piece of the puzzle.