Benchmarking soil thermal buffering for climate–smart adaptation in Australia

Climate change is increasing the frequency and intensity of thermal extremes, challenging agro-ecosystem resilience. Soil thermal buffering, the ability to moderate temperature fluctuations, is a critical yet under-mapped component of heat stress mitigation. We present the first continental-scale assessment of soil Thermal Inertia (TI) as an indicator of subsurface thermal buffering for Australia. Utilising pedogenon framework, we decouple inherent potential (capacity) from the current realised state (condition). TI was modelled for the upper 1 m soil profile by integrating volumetric heat capacity and thermal conductivity from national digital soil maps and 21-year mean moisture data. Spatial patterns reveal a distinct dichotomy with high TI clustered in the humid northern and eastern belts, whereas the arid interior exhibits low buffering. Inherent capacity was highest in Vertosols and Ferrosols, identifying these as key zones for root-zone thermal protection. However, the divergence between capacity and condition indicates that many soils currently function below their standardised potential, likely driven by long-term moisture limitation and land-use impacts. Validation against monthly soil temperature variance confirmed the physical realism of these estimates, showing strong inverse TI–temperature relationships, particularly in water-limited environments. Unlike common environmental variables, TI integrates multiple physical properties, offering a nuanced indicator of combined thermal–hydrological stress (“hot and dry” vs “dry”). With a basis for identifying inherently vulnerable soils and areas where current thermal buffering falls below potential, the findings provide a spatially explicit foundation for incorporating soil thermal buffering capability into drought and fire risk frameworks and climate-smart adaptation strategies.