Spatial uncertainty of 137Cs-derived net (1950s–1990) soil redistribution for Australia



[1] The caesium-137 (137Cs) technique has been used successfully in many parts of the world to estimate net (ca. 30–50 years) soil redistribution by wind and water erosion and tillage activities. The point-based technique has hitherto been confined largely to individual fields and hillslopes, particularly in Australia. Its application here to the Australian continent (≈5 km grid) was achieved using geostatistics and nationally coordinated measurements (early 1990s) from ≈200 locations at the ≈1 km scale. A map of the 137Cs reference inventory for Australia has been previously established. Sequential indicator co-simulation of the 137Cs inventory and the Australian Soil Classification was used to estimate net (between mid-1950s and early 1990s) soil redistribution using the Australian Empirical Model. This geostatistical approach showed that nearly five times more soil was lost from cultivated land (−4.29 to +0.17 t ha−1 yr−1) than from uncultivated (−0.91 to +0.05 t ha−1 yr−1) land in Australia. This information on spatial uncertainty is essential for regional soil management to assess the risk to soil conservation. Soil erosion exceeding a tolerable threshold value (e.g., 0.5 t ha−1 yr−1) occurred over 16% of Australia, mainly in cultivated regions (median = −1.26 t ha−1 yr−1). Soil erosion estimates are neglected in carbon balances for greenhouse gas abatement and carbon accounting models. Reliable quantitative data on the recent extent and rates of soil erosion are needed to underpin the selection of effective soil conservation measures, to inform carbon balances and to understand regional soil function for sustainable agricultural systems.