Agricultural ecosystem services under climate change – Modelling grassland biodiversity

European permanent grasslands not only represent a backbone for dairy and meet production, but also are hotspots of biodiversity, providing important ecosystem services to society. Understanding how climate variability and change affect the botanical composition of permanent grasslands is therefore essential for informing adaptation and helping farmers targeting sustainable development goals. It is also a key requirement for gauging climate change effects on forage quality, an aspect often overlooked in impact assessments. In this contribution, we present results of a modelling effort to understand short- and long-term changes in grassland biodiversity in response to climatic variations. We use DynaGraM, a recently developed process-based model for simulating community dynamics in multi-species managed grasslands. Earlier we demonstrated that DynaGraM is capable of representing the composition of permanent grasslands in the French Jura Mountains inferred from floristic relevés. In these earlier investigations, we also showed that the model predicts highest, resp. lowest vegetation diversity for extensive grazing, resp. extensive mowing. We further found that the time scales of responses to external perturbations largely dependent on management, with shorter time scales (of the order of 5 to 10 years) under grazing than under mowing (of the order of 50 years).

Here we apply the model to examine how increasing summer aridity affects the species composition of pastures in the same geographic area. To drive the model, we use a set of climate change scenarios obtained from the CMIP5 repository, which we downscaled with the help of the LARS-WG stochastic weather generator. The results underline that management intensity modulates the impact of summer drought on both yield as well as botanical diversity, with largest changes over time in the latter under extensive grazing. Apart from presenting the results in more detail, we also discuss their practical implications and opportunities to extend in future the scope of this work.