Dirty Solution to a Cleaner Future: Soil Carbon Sequestration

As atmospheric CO2 levels continue to climb, scientists are becoming interested in soil carbon sequestration, in which excess carbon is put back in the ground where it came from.

In 2018, passengers aboard the nuclear-powered 50 Years of Victory planted a time capsule in the Arctic. They figured it would be another 50 or so years before the ice melted and their photographs, letters, poems, and other early 21st century memorabilia would be discovered. One letter read “Everything around is covered by ice. We think that by the time this letter will be found there is no more ice in Arctic unfortunately.”

The author was right about the Arctic eventually melting, though he was wrong about how long it would take. In August, 2020, only 2 years later, the time capsule was found 2,300 miles away, washed up on the coast of Ireland.

In the last decade alone, the Arctic’s temperature has increased nearly 1C, with Greenland losing an estimated 1 million tonnes of ice every minute. Likewise, ocean temperatures are rising and climates are shifting around the world, leading to a rapid decline of biodiversity and displacing hundreds of millions of people. The Brooking Institute estimates that in 2017 alone “68.5 million people were forcibly displaced, more than at any point in human history.”

Among the many solutions to climate change, soil carbon sequestration is emerging as one of the most effective and the most feasible. Put simply, this mainly entails various methods of increasing plant growth, as an estimated 46% of total carbon fixation is due to root systems, the surrounding soil, and the microecosystems contained within. If implemented relatively soon, we have a chance of preventing positive feedback loops and tipping points, in which climate change accelerates well beyond our and other species ability to adapt.

The Basics of Climate Change

Earth’s climate is always changing. By looking at ice core samples, ancient tree rings, layers of sedimentary rocks, coral reefs, ocean sediment, etc., scientists from research institutions all over the world have found that in the last 650,000 years 7 cycles of warming and cooling have occurred, with the last one ending almost 12,000 years ago. Most of these cycles are due to wobbles in the Earth’s orbit around the Sun, leading to tiny changes in the amount of sunlight hitting the surface.

However, the overwhelming scientific consensus is that the current period of warming is due to excess carbon dioxide in the atmosphere from human activity, namely the burning of fossil fuels and poor land management. Since the late 19th century, Earth’s average temperature has risen roughly 2 degrees Fahrenheit, and most of this increase has happened in only the last 40 years. According to NASA, “Carbon dioxide from human activity is increasing more than 250 times faster than it did from natural sources after the last Ice Age.” Carbon dioxide is nearing 420 parts per million, well over the highest ever recorded.

Because of this excess carbon, the ocean temperatures are rising, ice sheets are shrinking, glaciers are retreating, snow cover is decreasing, ocean levels are rising, arctic sea ice is shrinking, extreme weather events are increasing, and the oceans are becoming more acidic. The National Oceanic and Atmospheric Administration claims “Things that we depend upon and value — water, energy, transportation, wildlife, agriculture, ecosystems, and human health — are experiencing the effects of a changing climate.” In fact, the 6th mass extinction is already underway, as species’ extinction rates are 1000 times more than natural, in part due to the crazy amount of microplastics being found virtually everywhere, even in the food chain.

Feedback Loops and Tipping Points

To make matters worse, climate change is accelerating due to positive feedback loops, in which increasing temperatures cause events that result in increasing temperatures. For example, rising temperatures cause the frozen peat bogs of Siberia to melt, which releases large amounts of stored carbon into the atmosphere, increasing temperatures even further. Also, the higher temperatures rise, the more likely forest fires become and the more likely it is that rainforests dry out, meaning the large amounts of carbon stored within gets released. Likewise, deserts continue to expand, as land use on their edges is often unsustainable and the area is vulnerable to shifts in climate, a process known as desertification. The Sahel region on the southern edge of the Sahara Desert is at extreme risk of desertification and has already displaced 60 million people, although this is being combatted by the Great Green Wall of Africa.

On the other hand, negative feedback loops slow the effect of climate change. For example, as the oceans increase in size, the amount of carbon that can absorb into it goes up. It then settles to the bottom where it is stored as rock, made into shells, etc. Furthermore, according to the principles of blackbody radiation, the hotter the Earth gets the heat it puts out grows with a power of 4, as shown by the Stefan–Boltzmann law. Also, the more CO2 is in the atmosphere and the warmer the temperature, the more conducive the environment is for plant growth, which of course, removes CO2 from the atmosphere.

Although, negative feedback loops help to slow climate change, they are dwarfed by the positive feedback loops. And if we continue to contribute to these positive feedback loops, we are at risk of hitting various tipping points, in which reversing change is thought be impossible. The Intergovernmental Panel on Climate Change suggests tipping point could be catastrophic. For example, rising ocean temperatures lead to the bleaching of coral reefs, causing the entire ecosystem to collapse. In the Great Barrier Reef “scientists measured an 89% drop in new corals,” much of which is due to bleaching, although some can be attributed to damage from shipping, improper waste disposal, and overfishing. Likewise, after a certain point, the melting of the Greenland ice sheet cannot simply be reversed, nor can the loss of permafrost, the shift in monsoons, among many others.

Our Soil Carbon Debt

Earth’s soil has lost an estimated 133bn tonnes of carbon since the dawn of agriculture 12,000 years ago, the majority of which happened in the last 200 years. Agriculture–whether for human or animal consumption–requires large tracts of natural land to be cleared and tilled. Doing so destroys root systems and releases stored carbon, upsetting the natural carbon balance.

Authors of a study published in the PNAS claim, “Roughly 50 million km² of soils are currently being managed to some degree by humans for food, fiber, and livestock production, leading to the declaration that we live on a ‘used planet.'” The authors found that this results in a global loss of 8.1% of the carbon stored in the soil. Moreover, agriculture is a major threat to global ecosystems because “it has transformed habitats and is one of the greatest pressures for biodiversity: of the 28,000 species evaluated to be threatened with extinction on the IUCN Red List, agriculture is listed as a threat for 24,000 of them.”

A recent example of this is the clearing of the rainforest in Brazil for cattle. From the Guardian: “5,800 sq km of forest is being felled in the Amazon and other areas annually to be converted into pasture used for cattle farming.” Likewise, roughly 50% of the North American Great Plains has been converted to cropland.

Soil Carbon Sequestration: Paying Back the Debt

Soil carbon sequestration includes 2 types of solutions: revitalizing already degraded land and preventing future degradation.

One revitalization method is to just let nature retake the area. For example, in the Amazon-Cerrado transition, where the Amazon rainforest meets the forest-savanna borderlands, researchers used carbon dating to look at the last 1,600 years of plant growth. They said “Our data indicate a regional increase in tree cover prior to modern deforestation, which could help inform conservation and management for climate change mitigation.” In other words, the area will inevitably bounce back once we allow it to do so. The problem, though, is that large companies like Cargill, JBS and Mafrig are not willing to curb their deforestation efforts.

Revitalization also includes planting more trees. Numerous projects have been developed in the last few years, including TrillionTrees.org. Their goal is to restore a trillion trees by 2050. Several other projects exist with similar goals, and there’s even a cryptocurrency that runs on people planting trees. One of the most ambitious projects is the Great Green Wall of Africa, which is an 8000km long band of vegetation that stretches from “Senegal to Djibouti, east-west across the entire continent of Africa, making it the largest living structure on the planet.” This project is meant to reclaim lands lost to unsustainable agriculture and desertification by implementing ancient farming techniques, reintroducing native livestock, revitalizing local economies, and employing the expertise and technology of Google, the United Nations, and many other international organizations and governments.

Preventing future land degradation is a bit more complicated because the human population is growing exponentially and arable land is limited. One solution is to increase agricultural efficiency. For example, Finnish researchers have found that “When the aim is to shift from a monoculture towards improved soil fertility, carbon sequestration and positive environmental impact, studies have shown that the best ways include increased plant cover, more diversified crops and crop rotation.” Another solution is to use biochar, a type of charcoal. When farmers incorporate biochar it can enhance soil carbon sequestration while providing significant co-benefits, such as nitrogen remediation, improved water retention and higher agricultural productivity,” according a recent study.

Another solution is change people’s eating habits. For instance, meat production is land intensive, as “Livestock takes up nearly 80% of global agricultural land, yet produces less than 20% of the world’s supply of calories.” Instead, people could look to other sources of protein, including synthetic meats like Power-to-Protein. Even McDonald’s is jumping on board with their “McPlant.” It would also be a good idea to stop buying products that contain palm oil, as many companies clear-cut rainforests for available space to grow palm trees.

Lastly, we need to get creative and rely on science. Instead of traditional farming techniques, we could use vertical farming, hydroponic farming, no-till farming, using integrated pest management, among many other examples. All of these would increase crop yields in a sustainable way.

Some experts believe we have already hit climate tipping points, while others believe they may be decades away. Either way, if the human species is going to continue to grow and evolve, we need to reduce the amount of carbon we put into the atmosphere. And soil carbon sequestration seems to be the best way to do this, although it may not be enough. We will likely need various methods of producing clean energy, such as artificial leaves, blue energy, wave energy, and of course solar and wind.

If you enjoyed the article, please consider donating a few bucks! Even a little bit helps keep independent journalism alive.