Nationwide soil erosion assessment in India using radioisotope tracers 137Cs and 210Pb: the need for fallout mapping

Abstract

Soil degradation induced by erosion represents a major threat to food production and ecosystem service globally, and in India more than 80 Mha have been impacted. In the light of the serious threat, there is a pressing need for a systematic nationwide assessment of land degradation due to erosion. We discuss the potential for using caesium-137 and lead-210 tracers to address this need and the next steps to realizing nationwide implementation. Globally soil erosion has reached a level that endangers the sustainable supply of food for the growing global population. It already threatens food production and ecosystem service delivery and therefore, there is a pressing need to address this threat. This is especially true in India where, in a total area of 328 million hectares (Mha), 121 Mha is undergoing soil degradation, 68% of which is attributed to water erosion1. Water erosion rates range from 5 t ha–1 yr–1 in dense forest regions to rates in excess of 80 t ha–1 yr–1 where erosion is most severe, such as in the Shiwalik mountainous region2. India’s average soil loss has been estimated to be 15 t ha–1 yr–1; however, given the limited coverage of measurements, this should be treated with caution. In the light of the serious threat that soil erosion poses in the country, there is a pressing need for a systematic nationwide assessment of land degradation due to erosion using appropriate techniques. Following the approach adopted by the United States Department for Agriculture (USDA) and employed by other organizations, the majority of soil erosion studies in India have used run-off plot measurements2. Such studies need substantial investment time