Onderzoek naar de effecten van klimaat- en landgebruiksverandering op het functioneren van ecosystemen door middel van eigenschapsmodellen en grote ecologische databases

Grasslands are among the most extensive and biodiverse terrestrial biomes in Europe, providing essential ecosystem functions and services that support both natural systems and human livelihoods. However, these ecosystems are increasingly threatened by accelerating climate change and land-use intensification, creating urgent challenges for biodiversity conservation and sustainable management. Although ecological theory highlights the central role of functional traits in linking environmental change to community composition and ecosystem functioning (EF), major knowledge gaps remain, particularly regarding how these relationships unfold at large spatial scales and under future scenarios. This thesis addresses these gaps by integrating joint species distribution models (JSDMs), trait-based approaches, large vegetation-plot databases, remote sensing, and multi-source environmental data to assess how environmental change is likely to reshape European grassland at the species level, trait level, and functioning level. In Chapter 2, I constructed stacked species distribution models (SDMs) and JSDMs to compare their modeling performance and predict the response of grassland communities to climate and land-cover change at the species level. The results demonstrate that European grassland species are likely to undergo extensive redistribution in the future, with pronounced species losses in mountainous regions and high turnover across Western, Northern, and Eastern Europe. While JSDMs did not improve predictive accuracy of species-level occurrence predictions compared with stacked SDMs, they substantially enhanced computational efficiency and better captured co-occurrence patterns, particularly for rare species. In Chapter 3, I applied JSMDs and evaluated the future status of Natura 2000 (N2K) grassland habitats according to the richness of indicator species under climate and land-cover change. The results reveal that a substantial proportion of grassland protected areas (PAs) are unlikely to meet their conservation objectives under future scenarios. Many sites, especially in northern and montane regions, are likely to experience widespread habitat contraction, highlighting the inadequacy of static conservation goals under dynamic environmental change. This chapter emphasizes the need for flexible, dynamic, and forward-looking planning to maintain the long-term resilience of Europe's grassland habitats. In Chapter 4, I predicted the response of grassland communities to climate and land-cover change at the trait level, including functional composition and functional diversity. The results show that mean annual temperature strongly shapes community-level traits and that future climates will drive shifts in plant height, leaf area, seed numbers, and functional richness (FRic). Notably, declines in FRic in temperate regions and reorganizations at high latitudes suggest emerging functional gaps that may alter EFs. Finally, in Chapter 5, I investigated the underlying mechanisms of the diversit-stability relationship based on functional components and satellite-derived measures of temporal stability. This chapter provides empirical evidence that functional traits, particularly those describing dominant acquisitive strategies and functional dispersion, better explain the temporal stability of grassland productivity than species richness alone. Compensatory dynamics contributed more to stability than the insurance effect, emphasizing the importance of maintaining or restoring species assemblages with complementary functional responses to improve ecosystem stability. Together, these findings indicate that European grasslands are likely to undergo substantial reorganization in both species distributions and functional composition, with far-reaching dynamic and future-based implications for ecosystem stability and conservation planning. This thesis advances understanding of the mechanisms underpinning ecosystem stability by demonstrating how functional traits govern temporal stability in grassland productivity through compensatory dynamics rather than species richness alone. Additionally, it underscores the value of trait-based approaches for conservation, which can provide greater precision in identifying functionally critical species or communities and in designing adaptive, climate-informed management strategies. Specifically, management should prioritize the protection of large-leaved species within microclimatic refugia and the maintenance of landscape mosaics that facilitate gene flow, while synchronizing grazing with post-seed-set periods to replenish soil seed banks. Furthermore, while increasing FRic identifies northern and mountainous regions as critical refugia, policy must utilize trait-based monitoring to mitigate invasion risks and preserve native functional assemblages. At the same time, several limitations emerge, including reliance on presence-absence data, limited representation of habitat degradation, spatial mismatches between plot- and pixel-level data, and gaps in available trait information, particularly for below-ground and intraspecific traits. Future research should therefore prioritize abundance-based modelling at large spatial scales, the development of high-resolution microclimate data for open ecosystems, and the integration of land-use intensity and quality into ecosystem models. By combining more comprehensive trait information with dynamic conservation planning, ecological forecasting can move closer to its long-standing goal of linking traits, environments, biodiversity, and EFs within a coherent predictive framework.