Global assessment of grassland carrying capacities and relative stocking
densities of livestock
Abstract
Although many suggest that future diets should include more plant-based
proteins, animal-sourced foods are unlikely to completely disappear from
our diet. Grasslands yield a notable part of the world’s animal protein
production, but thus far, there is no global insight into the
relationship between current livestock stocking densities and the
availability of grassland forage resources. This inhibits acting upon
concerns over the negative effects of overgrazing in some areas and
utilising the potential for increasing production in others. Previous
research has examined the potential of sustainable grazing but lacks
generic and observation-based methods needed to fully understand the
opportunities and threats of grazing. Here we provide a novel framework
and method to estimate global livestock carrying capacity and relative
stocking density, i.e. the reported livestock distribution relative to
the estimated carrying capacity. We first estimate the aboveground
biomass that is available for grazers on grasslands and savannas based
on the MODIS Net Primary Production (NPP) approach on a global scale.
This information is then used to calculate reasonable livestock carrying
capacities, using slopes, forest cover and animal forage requirements as
restrictions. With this approach, we found that stocking rates exceed
the forage provided by grasslands in northwestern Europe, midwestern
United States, southern China and the African Sahel. In this study, we
provide the highest resolution global datasets to date. Our results have
implications for prospective global food system modelling as well as
national agricultural and environmental policies. These maps and
findings can assist with conservation efforts to reduce land degradation
associated with overgrazing and help identify undergrazed areas for
targeted sustainable intensification efforts.