Managing grassland systems in a changing climate: the search for practical solutions.

By the end of the XXIst century, a global temperature rise between 1.5 and 4°C compared to 1980- 1999 and CO2 concentrations in the range 550-900 ppm are expected, together with an increased frequency of extreme climatic events (heat waves, droughts, and heavy rain) that is likely to negatively affect grassland production and livestock systems in a number of world regions. Grassland management has a large potential to mitigate livestock greenhouse gas emissions at a low (or even negative) cost, by combining a moderate intensification, the restoration of degraded pastures and the development of silvo-pastoral systems. Climate change vulnerability will be highest in regional hot spots with high exposure to climatic extremes and low adaptive capacity, such as extensive systems in dryland areas. Biome shifts, with expansion or contraction of the grassland biome, are projected by models. Resistance, resilience and transformation strategies can be used for grassland adaptation. With sown grasslands, adaptation options include changes in forage species (e.g. use of C4 grasses and of annual species) and genotypes and the use of grass-legume mixtures. Grazing management can be adapted to increase the resilience of plant communities to climatic variability. Our understanding of the synergies and trade-offs between adaptation and mitigation in the grassland sector is still limited and requires further research. Provided this understanding is gained, climate smart grassland systems that sustainably increase productivity and resilience (adaptation), reduce greenhouse gas emissions (mitigation), and enhance food security and development could be promoted. By reducing productivity gaps and increasing livestock production efficiency, they would also contribute to mitigate climate change from tropical deforestation and expansion of grasslands into savannahs. (Resume d'auteur)