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What’s Soil Got to Do with Climate Change?

Todd Longbottom, Leila Wahab, Dept. of Life and Environmental Sciences, University of California Merced, Merced, California 95343,
USA; Kyungjin Min, Dept. of Life and Environmental Sciences, University of California Merced, Merced, California 95343, USA, and
Center for Anthropocene Studies, Korea Advanced Institute of Science and Technology, Daejeon, South Korea; Anna Jurusik, Dept. of
Life and Environmental Sciences, University of California Merced, Merced, California 95343, USA; Kimber Moreland, Atmospheric,
Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA; Manisha Dolui, Touyee
Thao, Melinda Gonzales, Yulissa Perez Rojas, Jennifer Alvarez, Zachary Malone, Jing Yan, Teamrat A. Ghezzehei, and Asmeret
Asefaw Berhe, Dept. of Life and Environmental Sciences, University of California Merced, Merced, California 95343 USA

ABSTRACT Soils are a necessary part of the solution for is driven by microbial decomposition of
Soils are the foundation of life on land human-induced climate change because they organic C inputs to CO and dissolved and
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and represent one of the largest global represent one of the largest terrestrial car- particulate transport of C through leaching
carbon (C) reservoirs. Because of the vast bon (C) reservoirs, storing twice as much C and/or erosion.
amount of C that they store and the continu- as the earth’s atmosphere and vegetation The SOC that exists in soil can be subdi-
ous fluxes of C with the atmosphere, soil combined (up to 2500 Pg C; IPCC, 2013; vided into “slow-cycling” and “fast-cycling”
can either be part of the solution or problem Friedlingstein et al., 2020). Terrestrial C pools akin to checking and savings accounts
with respect to climate change. Using a pools are a powerful C sink, with the poten- (Lavallee and Cotrufo, 2020), respectively.
bank account analogy, the size and signifi- tial to offset up to 30% of anthropogenic C Slow-cycling C is either mineral-associated
cance of the soil organic C (SOC) pool is emissions, where some of the sequestered C C that is found physically protected in soil
best understood as the balance between persists in soil over millennial time scales aggregates or chemically bound to the sur-
inputs (deposits) from net primary produc- (Friedlingstein et al., 2020). Because of the faces of reactive soil minerals; both mecha-
tivity and outputs (withdrawals) from SOC relative sizes of the different C reservoirs, nisms restrict decomposition and associated
through decay and/or physical transport. even slight changes in the amount of C losses of SOC, allowing it to persist in soil
Reversing the current problematic trend of stored in soil can represent significant for decadal to millennial time scales (Schmidt
increasing concentration of greenhouse changes in the global atmospheric con- et al., 2011; Hemingway et al., 2019). In
gases in the atmosphere must be met with centration of carbon dioxide (CO ) and contrast, fast-cycling C is more readily
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reduced fossil fuel emissions. At the same the earth’s climate future. degradable and prone to physical transport
time, we argue that “climate-smart” land How do we unlock soil’s potential for in shorter time scales (Schmidt et al., 2011;
management can promote both terrestrial combating climate change? An important Hemingway et al., 2019). Fast C cycling,
sequestration of atmospheric carbon diox- component of a comprehensive response is which is akin to funds in a checking account,
ide (CO ) and contribute to improving soil to store more C in soils, particularly in soil is critical for maintenance of life in soil,
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health and benefits. In this review, we high- pools that cycle C at slower rates compared because decomposition is the main mecha-
light environments that are particularly vul- to the other reservoirs (ex., atmosphere, bio- nism that recycles nutrients needed by organ-
nerable to SOC destabilization via land use mass, and on near surface soil layers) isms that call the soil home (Janzen, 2006).
and climatic factors and outline existing (Schmidt et al., 2011). The amount of carbon Even small, but sustained, deposits into the
and emerging strategies that use soils to stored in soil (soil organic C or SOC) is a soil C savings account over time allow for
address anthropogenic climate change. balance between inputs and outputs of car- long-term buildup of C in the slow-cycling
bon (Berhe, 2019a; Lavallee and Cotrufo, pool with significant potential for climate
INTRODUCTION 2020). SOC storage in a given area (plot, change mitigation.
The health and diversity of natural eco- catchment, region, or another spatially con- Increasing urgency for addressing the
systems—and human civilization—depend strained system) has been likened to a bank global climate emergency demands that we
on our coordinated responses to global account, where the “balance” is the bulk reduce the release of greenhouse gasses
changes that threaten earth’s long-term SOC stock or inventory (Fig. 1). Bank from burning of fossil fuels, while finding
habitability. Soils, the thin veneer on the “deposits” are contributed by vegetation lit- appropriate alternatives to draw down some
global land surface that supports terrestrial ter, root exudates, living soil biota, deposi- atmospheric carbon through soil carbon
life, are an integral component of anthropo- tion of eroded C, and remains of formerly sequestration and other means. As we seek
genic climate change mitigation strategies living organisms. The depletion of the these solutions, it is important to remember
(Paustian et al., 2016; Loisel et al., 2019). balance in the soil carbon bank account that decomposition of organic matter (i.e.,

GSA Today, v. 32, https://doi.org/10.1130/GSATG519A.1. CC-BY-NC.

4 GSA TODAY | May 2022