Towards soil security: Understanding soil erosion footprints and their implications in NSW

A key challenge in maintaining soil security is assessing and mitigating soil degradation. The soil footprint is a promising indicator for quantifying degradation impacts, yet it remains underdeveloped, lacking a standardized definition and a comprehensive calculation framework. This study introduces a generalized soil footprint framework, integrating three key components: (1) Threat to soil, representing degradation processes such as soil water erosion or salinization; (2) Soil service ratio, which quantifies changes in soil services such as crop yield or Available Water Capacity relative to their natural state; and (3) Inherent mitigation capability, reflecting the soil's resilience to degradation. Applied in New South Wales (NSW), Australia, we calculated two soil erosion footprints using crop yield and Available Water Capacity (AWC) as indicators of soil services. In both cases, soil erosion rate, specifically water erosion, was used as the threat to soil, while erosion risk capability represented the soil's intrinsic mitigation capacity. Results show that oats had the highest soil erosion footprint due to lower yields, whereas wheat, barley, sorghum, and grain legumes had smaller footprints. An inverse relationship between soil erosion footprint and crop receipts (i.e., farm revenue from crop production) highlights the economic risks of soil erosion, particularly in high-revenue regions like the Northwest Slopes and Plains and the Riverina. AWC-based soil erosion footprints were highest in coastal and dryland cropping areas, indicating greater erosion stress, while irrigated systems, plantation forests, and managed resource protection areas showed lower footprints, reflecting better resilience. Modified pastures, native forests, nature conservation areas, and minimal-use lands had higher footprints. This study highlights the need to integrate soil service ratios and erosion risk capability alongside erosion rates for a more comprehensive approach to soil sustainability and mitigation strategies. The proposed soil footprint framework provides a valuable tool for evaluating human impacts on soil services, guiding targeted soil conservation efforts.