Globally, aridlands span diverse ecosystems on all continents and comprise over 40% (i.e., 6.1 Bn ha) of Earth’s terrestrial surface. Unfortunately, aridlands remain vastly understudied relative to their area (e.g., tropical ecosystems ~ 4% of Earth’s terrestrial surface, 6.4 M ha), and especially lacking are studies and datasets on aridland soils. Important to climate change mitigation is a thorough understanding of aridland soil biogeochemistry, including soil organic carbon (SOC) and inorganic carbon (SIC). For example, global SOC estimates range between 504 and 3,000 Pg and an estimated 97% of terrestrial SIC (~ 800 Pg) occurs within arid regions. In this study, our goals are to (1) synthesize studies and geospatial datasets elucidating our understanding of the distribution, nature, and extent of SOC and SIC in aridlands globally, (2) identify areas of the Earth where such data is lacking, incomplete, or of poor quality, and (3) harmonize aridland SOC and SIC geospatial datasets to better understand the role of SOC and SIC in aridlands at the global-scale and the vulnerabilities of these pools under future land-cover and climate change scenarios. We performed a literature and data (high-resolution soil and aridity) review across various online article and data repositories.
We found 371,923 environmental studies of aridlands (compare to 454,496 tropical studies), of which 129,675 included the term “soil” published between 1900 and 2015 (Web of Science). Of these studies, approximately 9,000 (7.0% of all soil studies) included the term “soil organic” (or “organic soil”) while less than 200 (0.2%) included the term “soil inorganic” (or “inorganic soil”). All studies represent investigations across a diverse spectrum of environmental aridity: hyperarid, arid, semiarid, and dry sub-humid climates. Our review of aridland soil datasets revealed heterogeneity in scale, between 1:12,000 (e.g., SSURGO [US]) to 1:5,000,000 (WISE30sec [global]), and in resolution, from 10 meters to > 1 kilometer, created at different times by a variety of organizations, and produced for unique purposes, underscoring the role of harmonization for comparison. We report preliminary findings of data synthesis and harmonization efforts. Currently, 35% of the human population and 44% of all agricultural activities are concentrated in aridlands, underscoring the importance of quantifying and mapping SOC and SIC across dryland environments where human population, food production, and energy development are likely to expand.