Debunking 3 Soil Carbon Myths

2016 can certainly be recognized as a year of progress for U.S. soil conservation and restoration. In May, Congressional Representative Jared Huffman (CA 2nd District) introduced the Healthy Soils and Rangelands Solutions Act to create a pilot payment program to incentivize the sequestration of carbon on public lands. In August, the approval of California’s SB 859 established The Healthy Soils Initiative, a California Department of Food and Agriculture (CDFA) led program to farmers for management practices that protect soils and reduce net greenhouse gases from agriculture. Near the end of the year, the White House Office of Science and Technology Policy released a Framework for a Federal Strategic Plan for Soil Science, providing a much-needed summary of present research, technological demands, best land management practices, and social drivers around soil conservation and restoration. 

While there has been noteworthy progress on soil policy, there is still a great deal of work to be done to support the development and implementation of soil carbon sequestration practices in a realistic, verifiable manner. Progress, however, is hindered by a number of myths about soil carbon that continue to circulate, both from advocates and skeptics. Below we debunk three common misconceptions about soil carbon and set the facts straight about the efficacy of soil carbon sequestration as a tool to fight climate change.

 

Myth #1: The soil carbon reservoir is a fix-all climate solution.

While soil carbon is our largest terrestrial carbon reservoir, some sequestration advocates tend to gloss over the complicating factors that can affect sequestration projections in scientific model results. These data-limited projections still require continued research, implementation, and supervision, and therefore justify the celebration of soils as an important tool, but not a universal solution to climate change.

While it is positive that prominent research in soil carbon sequestration has indicated a substantial storage potential for U.S. soils, theoretical projections like the French “4 Per 1000” Initiative and others found in studies that extrapolate the global potential for soil carbon sequestration could be misconstrued if the management requirements and timelines for these pathways are not clearly articulated to stakeholders. A recent study in Science Magazine found that climate models may overestimate the speed at which carbon cycles through soil. The study expanded on IPCC models, using radiocarbon dating to demonstrate that previous climate projections had assumed an unusually rapid cycling of soil carbon. The lead author of the study, Yujie He, stated that “it will take a very long time for soil to soak up the carbon; there is a timescale mismatch in terms of climate change.” In a 2016 letter, Dr. Ronald Amundson echoed this skepticism, explaining that soil carbon sequestration programs often oversimplify soil sequestration by omitting factors like the microbial slowing of carbon intake and stakeholder disorganization. He explains that “the biggest sequestration of carbon occurs at the beginning of a management change, and it quickly grinds down to no net gain.” While scientists may still be working through the microbial nuances of soil’s carbon flux, these calculation refinements are not an indication that soil is not worthy of our attention, but rather a signal that it needs a more comprehensive analysis in order to contribute alongside other mitigation strategies.

 

Myth #2: We should focus on emissions reductions before we worry about soil carbon sequestration.

This is a false choice. In reality, these two efforts must happen simultaneously, since increases in average global temperatures due to climate change can cause the loss of carbon currently stored in soils. These added emissions from the soil would exacerbate the climate problem, starting a feedback cycle between warming and soil carbon emissions. Failure to act now to effectively manage the carbon currently stored in soils could undermine our efforts to reduce emissions elsewhere.

This initial statement presumes that we can’t do two things at once, and that soil carbon management is somehow at odds with reductions in other sectors. Failure to adequately protect soil carbon from disturbance and warming can result in increased emissions, making intervention to protect global soils increasingly necessary. This is especially important consdering that 50-70% of carbon in cultivated lands has already been released, further perpetuating warming. A Yale Forestry report states “that warming will drive the loss of at least 55 trillion kilograms of carbon from the soil by mid-century, or about 17% more than the projected emissions due to human-related activities during that period.” Dr. Amundson commented that “the real concern about soils is the positive feedbacks that will likely occur this century, and the additional greenhouse gases soils will emit due to warming.” This feedback also has repercussions for the benefits of healthy soils (such as increased crop production, recreation, and other ecosystem services) since they are contingent upon a well founded structure of high soil organic carbon density. Regarding soil exclusively as an negative emissions strategy not only fails to acknowledge its multitude of other crucial services, but excludes the positive emissions emitted from U.S. soils as a result of unsustainable agriculture, overgrazing, development, biomass loss, and climate change.

Healthy, undisturbed soils with dense biomass and root structures will slowly store carbon from the atmosphere in the soil (left). However, when that biomass is lost, soil is disturbed, and/or land is deforested, carbon stored in the soil is released back to the atmosphere (right). 

Healthy, undisturbed soils with dense biomass and root structures will slowly store carbon from the atmosphere in the soil (left). However, when that biomass is lost, soil is disturbed, and/or land is deforested, carbon stored in the soil is released back to the atmosphere (right). 

Myth #3: Soil carbon sequestration is at odds with productive agriculture and other human activities.

Carbon farming and regenerative agriculture present techniques which incorporate soil carbon priming methods and consistent groundcover to maximize agricultural yields, soil fertility, and profit.

Even if we are to consider our nation's soils as a long term strategy for climate stabilization, there is a plethora of co-benefits associated with increasing and protecting carbon in soils. These benefits include increased fertility, water availability, and erosion resilience and are typically beneficial for agricultural productivity. Recent studies establishing carbon farming as a potential synthesis between sequestration and economic productivity in Bioscience and Environmental Science and Policy have supported the idea that soil sequestration can be a win-win strategy in U.S. and international climate mitigation efforts. Carbon-sequestering farming practices like polyculture, low- and no-till farming, and enhancing organic material through the addition of compost are all ways in which farming can be compatible with preventing carbon loss and even sequestering carbon into U.S soils. In an interview, Kristin Ohlson, author of the “The Soil Will Save Us,” articulated the basic principles succinctly: “we want to disturb the soil as little as possible, we want to have as much vegetation growing as densely as possible, and we want that vegetation to be as diverse as possible." In this respect, carbon sequestration and storage in U.S. soils can be aligned with sustainable and profitable food production, improved soil resilience and health, and increased soil fertility.    

Soil organic carbon (SOC) offers climate as one of several interconnected benefits. Each of these necessary elements is integrally linked and dependent upon preserved and even enhanced soil carbon (International Institute of Tropical Agriculture 2015).  

Soil organic carbon (SOC) offers climate as one of several interconnected benefits. Each of these necessary elements is integrally linked and dependent upon preserved and even enhanced soil carbon (International Institute of Tropical Agriculture 2015).  

All in all, our soils can play a pivotal role in fighting climate change, but we need to act today to protect and restore their carbon-storing capacity. Increased science to understand soil carbon sequestration dynamics, swift action to protect existing soil carbon stocks, and increased stakeholder engagement to connect healthy, productive soils to climate protection will be key in realizing their full potential.