Interactive Effects of Land-Use Intensification and Climate Extremes on Grassland Biodiversity and Stability

We urgently need to understand how land-use intensification and anthropogenic climate change drive ecosystem decay and biodiversity loss. In temperate grasslands, intensive land-use typically reduces plant diversity but enhances productivity by favoring resource-acquisitive, fast-growing species. Previous studies suggested that more diverse communities harboring more slow-growing species should be more resistant to climatic stress. Yet, how land-use intensity mediates plant community responses—such as diversity, biomass, and stability—to increasingly frequent and severe climate extremes remains poorly understood. In this study, we integrate annual vegetation surveys, standardized land-use indices, and daily temperature and precipitation data from 150 grasslands in Germany (The Biodiversity Exploratories) with high-resolution reconstructions of daily historical climate variability since 1950. Land-use intensity was quantified through standardized indices of fertilization, mowing, and grazing levels, allowing us to link management regimes to multi-decadal patterns of climatic stress. We identify and quantify the frequency, duration, and intensity of multiple extreme events (e.g. heatwaves, droughts, cold spells) over the past 75 years and assess how the diversity of aboveground plants, their traits, and their biomass production respond to these climatic stressors under varying land-use intensities since 2008. Our reconstructions show a dramatic rise in severe drought occurrence, from an average of 0.20 months of severe drought per year over the 1990–2006 period to 3.19 months of severe drought months over 2008–2024 - a 1’495% increase in mean annual drought exposure. Over the latter period, aboveground biomass declined significantly (–8.3 ± 0.8 g m^-2 yr⁻¹), whereas species richness increased (+0.41 ± 0.16 species yr⁻¹). Biomass losses were strongest in intensively managed grasslands (–9.8 ± 0.8 g m^-2  yr⁻¹), suggesting that land-use intensification amplifies long-term biomass declines under increasingly dry conditions. Although intensively managed grasslands show lower plant species richness, they also showed the fastest gains in richness through time. Land-use categories had no detectable effect on the rates of plant biomass resistance or recovery from droughts. Our results highlight how increasingly frequent and severe droughts, in combination with intensive land-use, threaten the biomass production and stability of grassland ecosystems across Central Europe.