Global Grazing Systems: Their Continuing Importance in Meeting Global Demand

Tuesday, 16 December 2014
Kyle Frankel Davis, University of Virginia, Charlottesville, VA, United States and Paolo D'Odorico, Univ Virginia, Charlottesville, VA, United States
Animal production exerts significant demand on land, water and food resources and is an extensive means by which humans modify natural systems. Demand for animal source foods has more than tripled over the past 50 years due to population growth and dietary change. To meet this demand, livestock intensification (e.g. concentrated animal feeding operations) has increased and with it the water, nitrogen and carbon footprints of animal production. However, grass-fed systems continue to contribute significantly to overall animal production. To date, little is known about the contributions of grass- and grain-fed systems to animal calorie production, how this has changed through time and to what extent these two systems are sensitive to climate. Using a calorie-based approach we hypothesize that grain-fed systems are increasing in importance (with serious implications for water and nutrient demand) and that rangeland productivity is correlated with rainfall. Our findings show that grass-fed systems made up the majority of animal calorie production since 1960 years but that the relative contribution of grain-fed system has increased (from 27% to 49%). This rapid transition towards grain-fed animal production is largely a result of changing diets demand, as we found the growth of grass-fed production only kept pace with population growth. On a regional scale, we find that Asia has been the major contributor to the increase in grass-fed animal calorie production and that Africa has undergone the most drastic transition from grass-fed to grain-fed dependence. Finally, as expected we see a positive relationship between rangeland productivity and precipitation and a shift from dairy- to meat-dominated production going from drier to wetter climates. This study represents a new means of analyzing the food security of animal products and an important step in understanding the historic trends of animal production, their relation to climate, their prospects for the future and their implications for freshwater resources and nutrient cycling.