Genosoil and phenosoil mapping in continental Australia is essential for soil security

The intensification of human pressures on soil can reduce pedodiversity and decrease soil multifunctionality impacting soil security. Mapping genosoils (least modified soils within a soil class or soil map unit by contemporary drivers of soil change) and phenosoils (variants resulting from land use history and management) can be a preliminary step for quantifying soil security dimensions and prioritising areas for soil preservation and regeneration. Genosoil properties can be used as a baseline for assessing the effects of management on soil condition for a particular pedological, climatic and landscape context. In this study, we stratified Australia into 1370 pedogenons (i.e., groups with relatively homogeneous environmental covariates, proxies of soil-forming factors) that represent soil classes prior to the European settlement from 1788 onwards. We overlayed the maps of global Human Modification and the Habitat Condition Assessment System for Australia for identifying areas with minimum human influence on terrestrial ecosystems and soils. Areas with very low human influence were defined as genosoils at the continental level. The percentage of land mapped as genosoils accounted for 56% of the continent and had a median area of 2550 km². There were 32 pedogenon classes that did not have any remaining genosoils while 218 pedogenon classes had less than 5% of their area as genosoils. The proportion of genosoils protected in conservation areas or managed resource protection varied widely, although almost 25% of the genosoils had at least half of their area under conservation. In addition to soil multifunctionality, the criteria for prioritising soil conservation areas could consider: 1) endangered genosoils and 2) genosoils closest (in the scorpan feature space) to the phenosoils without an existing reference soil.