Dung predicts the global distribution of herbivore grazing pressure in drylands

Abstract

Dryland grazing sustains millions of people worldwide but, when poorly managed, threatens food security. Here we combine livestock and wild herbivore dung mass data from surveys at 760 dryland sites worldwide, representing independent measurements of herbivory, to generate high-resolution maps. We show that livestock and wild herbivore grazing is globally disconnected, and identify hotspots of herbivore activity across Africa, the Eurasian grasslands, India, Australia and the United States. Wild herbivore dung mass was negatively correlated with total organic nitrogen, yet strong site-level correlations exist between our livestock dung estimates and total soil organic nitrogen. Using dung mass as a proxy of herbivore abundance enables standardized, field-based measures of grazing pressure that account for different herbivore types. This can improve herbivore density modelling and guide better management practices for populations that rely on dryland-grazing livestock for food. Global maps of dryland livestock and wild herbivore dung mass show that dung can be used as a proxy for herbivory to improve herbivore density modelling and guide dryland management strategies.