Global trends in grassland carrying capacity and relative stocking density of livestock

Abstract

Although the role of livestock in future food systems is debated, animal proteins are unlikely to completely disappear from our diet. Grasslands are a key source of primary productivity for livestock, and feed-food competition is often limited on such land.Previous research on the potential for sustainable grazing has focused on restricted geographical areas or does not consider inter-annual changes in grazing opportunities. Here, we developed a robust method to estimate trends and interannual variability (IV) in global livestock carrying capacity (number of grazing animals a piece of land can support) over 2001-2015, as well as relative stocking density (the reported livestock distribution relative to the estimated carrying capacity [CC]) in 2010. We first estimated the aboveground biomass that is available for grazers on global grasslands based on the MODIS Net Primary Production product. This was then used to calculate livestock carrying capacities using slopes, forest cover, and animal forage requirements as restrictions. We found that globally, CC decreased on 27% of total grasslands area, mostly in Europe and southeastern Brazil, while it increased on 15% of grasslands, particularly in Sudano-Sahel and some parts of South America. In 2010, livestock forage requirements exceeded forage availability in northwestern Europe, and southern and eastern Asia. Although our findings imply some opportunities to increase grazing pressures in cold regions, Central Africa, and Australia, the high IV or low biomass supply might prevent considerable increases in stocking densities. The approach and derived open access data sets can feed into global food system modelling, support conservation efforts to reduce land degradation associated with overgrazing, and help identify undergrazed areas for targeted sustainable intensification efforts or rewilding purposes.

Protein and energy from grazing or crops - does livestock have a chance?

“…Similarly, steep slopes can limit grazing possibilities. Therefore, in line with Piipponen et al (2022), our calculation of AGB was reduced in areas where tree cover or steep slopes were present. Contrary to Piipponen et al (2023), however, we further reduced AGB by using the proper use factor (PUF) that reveals how large a share of the biomass animals can sustainably eat.…”

“…Lastly, we followed the approach described by Piipponen et al (2022) to adjust our calculation of AGB.…”

Effects of land use and soil properties on taxon richness and abundance of soil assemblages

“…For most land uses there was no clear pattern with either metric with use intensity, which probably reflects the qualitative nature of these classes. Future models could incorporate quantitative measures of intensity, for example, relative stocking density for grazed land (Piipponen et al, 2022) which may give more informative results.…”

Steps to operationalize a rewilding decision: Focus on functional types

“…Then, the diluting effect of rainfall means decreasing forage quality in wetter savannas, depressing herbivore biomass density from its peak of ~1,700 kg/km 2 (for wildlife excluding elephants, Loxodonta africana) in areas receiving >700 mm of mean annual rainfall (Hempson et al, 2015). Also, on a global scale, potential stocking rates can be estimated from remotely sensed data on net primary production in grasslands (Piipponen et al, 2021), although that underestimates community biomass because browsing is not accounted for.…”