Global risk of heat stress to cattle under climate change.

Abstract Livestock comprise the largest mammalian biomass on Earth and contribute to global food security. However, despite numerous case studies reporting heat impacts, the global risk of heat-related stress to livestock from climate change remains unquantified. Here, we conducted a global synthesis of documented heat stress in cattle to identify heat thresholds associated with decreased production and fertility, and increased mortality, and mapped these conditions worldwide for current and future climates. We find that unmitigated climate change will increase the duration of multiple-month heat stress outside the tropics whereas severity will increase most in the tropics and sub-tropics. Our results show that development pathways expanding cattle production into tropical forest regions in South America and Africa will both exacerbate climate change and expose hundreds of millions more cattle to increased heat stress, highlighting the contradiction of pursuing land-use practices that are themselves placed at high risk from resulting future climate hazards.