What’s Soil Got to Do with Climate Change?

Abstract

Soils are the foundation of life on land and represent one of the largest global carbon (C) reservoirs. Because of the vast amount of C that they store and the continu-ous fluxes of C with the atmosphere, soil can either be part of the solution or problem with respect to climate change. Using a bank account analogy, the size and signifi-cance of the soil organic C (SOC) pool is best understood as the balance between inputs (deposits) from net primary produc-tivity and outputs (withdrawals) from SOC through decay and/or physical transport. Reversing the current problematic trend of increasing concentration of greenhouse gases in the atmosphere must be met with reduced fossil fuel emissions. At the same time, we argue that “climate-smart” land management can promote both terrestrial sequestration of atmospheric carbon dioxide (CO 2 ) and contribute to improving soil health and benefits. In this review, we highlight environments that are particularly vulnerable to SOC destabilization via land use and climatic factors and outline existing and emerging strategies that use soils to address anthropogenic climate change. Here, three contrasting eco- systems reveal differing SOC richness and dynamics: (A) agricultural, (B) grassland/shrubland, and (C) forested. Conventional agriculture (A) often leads to lower carbon stocks, and overall, less carbon input to the soil carbon pool. Grasslands (B) can harbor plants with deeper and more extensive root systems, medium to high amounts of SOC stock, and greater carbon inputs to the SOC pool. Forests (C) can have the deepest rooting system, a high amount of soil C stock, greatest density of mineral-associated C, and high rate of input of C to soils. Overall, organo-mineral association(s) and SOC pool is a function of the “balance” of C inputs and outputs in the soil organic carbon “bank account.”