Climate change effects on grassland carrying capacity: a multi-model global analysis

The global food system is facing the task of sustainably feeding a growing population under the effects of climate change. Amidst concerns about its environmental impact, the livestock sector plays a crucial role in addressing this challenge, serving as a vital element for the food security and economic well-being of millions. Grasslands are an essential source of forage for livestock, accounting for half of the total biomass consumed by the entire livestock industry. Currently, a considerable portion of global grasslands already suffers from degradation due to inappropriate grazing practices, and overgrazing issues are anticipated to exacerbate with increasing demand for livestock products. Consequently, the response of grasslands to climate change will determine the extent to which increasing anthropogenic pressures will impact the health of these ecosystems. This analysis combines future projections of net primary productivity from five distinct vegetation models to obtain a robust estimation of climate change effects on grasslands carrying capacity (number of grazing animals a piece of land can support). The results indicate that rising temperatures and CO2 levels will have a generally positive effect on carrying capacity, thereby implying some opportunities to increase grazing pressures. Negative hotspots, where vegetation productivity is projected to decline, will primarily be concentrated in the Horn of Africa, Australia, Brazil, and Central America, affecting only a small fraction of the world's grasslands. However, despite this overall positive outlook, climate change will generate additional challenges due to the increasing severity, frequency and duration of extreme events. In particular, the adaptation to low-productivity years will become more challenging in most of the world’s grasslands, sometimes exacerbated by declining annual minimums. Furthermore, the inter-annual variability of carrying capacity will increase for over 70% of grasslands worldwide. This implies that the productivity of these grasslands will become more variable from year to year. Failure to effectively address these challenges through appropriate adaptation strategies may eventually offset the benefits derived from increased productivity. Moreover, considerations regarding the effects of climate change on forage quality and livestock health, may further diminish the benefits of projected productivity gains. Nevertheless, the results of this analysis provide crucial insights into future threats and opportunities for livestock production, serving as valuable tools for the development of policies aimed at preserving grassland resources in response to the growing demand for animal products.