Valuation of Total Soil Carbon Stocks in the Contiguous United States Based on the Avoided Social Cost of Carbon Emissions

Abstract

Total soil carbon (TSC) is a composite (total) stock, which is the sum of soil organic carbon (SOC) and soil inorganic carbon (SIC). Total soil carbon, and its individual two components, are all important criteria for assessing ecosytems services (ES) and for achieving United Nations (UN) Sustainable Development Goals (SDGs). The objective of this study was to assess the value of TSC stocks, based on the concept of the avoided social cost of carbon dioxide emissions, for the contiguous United States (U.S.) by soil order, soil depth (0–20, 20–100, 100–200 cm), land resource region (LRR), state, and region using information from the State Soil Geographic (STATSGO) database. The total calculated monetary value for TSC storage in the contiguous U.S. was between $8.13T (i.e., $8.13 trillion U.S. dollars, where T = trillion = 1012) and $37.5T, with a midpoint value of $21.1T. Soil orders with the highest TSC storage midpoint values were Mollisols ($7.78T) and Aridisols ($2.49T). Based on area, however, the soil orders with highest midpoint TSC values were Histosols ($21.95 m−2) and Vertisols ($5.84 m−2). Soil depth was important, with the highest values of TSC storage being found in the interval 20–100 cm ($9.87T—total midpoint value, and $1.34 m−2—midpoint area density). The soil depth interval 0–20 cm had the lowest TSC storage ($4.30T) and lowest area-density ($0.58 m−2) value, which exemplifies the prominence of TSC in the deeper subsurface layers of soil. The LRRs with the highest midpoint TSC storage values were: M—Central Feed Grains and Livestock Region ($2.82T) and D—Western Range and Irrigated Region ($2.64T), whereas on an area basis the LRRs with the highest values were I—Southwest Plateaus and Plains Range and Cotton Region ($6.90 m−2) and J—Southwestern Prairies Cotton and Forage Region ($6.38 m−2). Among the U.S. states, the highest midpoint TSC storage values were Texas ($4.03T) and Minnesota ($1.29T), while based on area this order was reversed (i.e., Minnesota: $6.16 m−2; Texas: $6.10 m−2). Comprehensive assessment of regulating ES requires TSC, which is an important measure in achieving the UN SDGs. Despite the known shortcomings of soil databases, such as their static nature and the wide ranges of uncertainty reported for various soil properties, they provide the most comprehensive information available at this time for making systematic assessments of ecosystem services at large spatial scales.

Soil Diversity (Pedodiversity) and Ecosystem Services

“…It also can be used to analyze the patterns of value for regulating ES. Mikhailova et al (2019) [35] provided a valuation of soil organic carbon (SOC) stocks in the contiguous U.S. based on taxonomic pedodiversity and the avoided social cost of carbon (SC-CO 2 ) emissions, which varied by the degree of soil weathering as indicated by soil order information. This study found the following distribution of SC-CO 2 contribution within the contiguous U.S.: slightly-weathered soils (38%), intermediately-weathered soil (51%), and strongly-weathered soils (11%).…”

“…This study found the following distribution of SC-CO 2 contribution within the contiguous U.S.: slightly-weathered soils (38%), intermediately-weathered soil (51%), and strongly-weathered soils (11%). In another example, according to Mikhailova et al (2019) [36], Mollisols have the highest total soil carbon (TSC, soil organic + soil inorganic carbon) storage midpoint value ($7.78T) based on the social cost of carbon (SC-CO 2 ) and avoided emissions provided by carbon sequestration, which is about 30% of the total midpoint value for the contiguous U.S. These types of analyses are useful in identifying soil "hotspots" with regards to various ES/ED applications at different scales which has the potential to be managed with precision agriculture [2,37].…”

“…There are numerous challenges in using appropriate soil data sources and valuation methods for soil properties. For example, Mikhailova et al (2019) [47] compared field sampling and soil survey database for spatial heterogeneity in surface granulometry (sand, silt, and clay) for potential use in ES/ED valuations and concluded that field sampling provided more detailed information. The same study revealed that soil texture and coarse fragments are lithospheric-derived resources (Figure 1) and can be valued based on "soil" or "mineral" stock.…”

Soil Carbon Regulating Ecosystem Services in the State of South Carolina, USA

“…These analyses allowed estimation of potential social costs of soil carbon, which is useful for decision-making at the national level using detailed tables and maps of social costs of C showing areas with high soil C content, which can become "soil carbon hotspots" upon disturbance [10]. At the national level, the analysis showed that states have different types of soils with various soil C types (e.g., Maryland is dominated by SOC, state of New Mexico is dominated by SIC) [11], which requires soiland carbon-specific management strategies. Some states demonstrated more soil variability compared to others.…”

Determining farm-scale site-specific monetary values of “soil carbon hotspots” based on avoided social costs of CO 2 emissions

“…Application of the monetary valuation of social costs and avoided social costs also depends on the user, goal, scale of the assessment, and the available data (e.g., soil survey databases, intensive field soil sampling data, etc.). For example, Mikhailova et al (2019aMikhailova et al ( , 2019b and Groshans et al (2019), reported monetary values of the avoided social cost of CO 2 emissions from SOC, SIC, and TSC stocks in the contiguous United States by soil order, soil depth, land resource region, state, and region based on data from Guo et al (2006). This type of assessment, using information from the State Soil Geographic (STATSGO) database, has a great degree of generalization which is suitable for country-level valuation but it is of limited application at the field or farm scales.…”