Drier, darker and more fertile: 140 years of plant habitat change driven by land‐use intensification

Questions Land‐use change is a key driver of biodiversity change. Delayed biotic responses to land‐use change impede the establishment of causal links between specific anthropogenic changes and resulting biodiversity change. Therefore, we aimed at investigating changes to plant species pools: (a) at time scales long enough to encompass past land‐use changes, even changes that have ceased from collective memory; and (b) at spatial scales wide enough to encompass landscape‐wide changes to habitat quantity and quality. Location Denmark, 10 regions in the range 54°3′–56°7′ N and 10°4′–12°4′ E. Methods We assessed changes to regional plant species pools over ca 140 years by comparing high‐quality legacy data to recent re‐surveys in ten Danish regions. To identify anthropogenic drivers of plant compositional change, we assessed ecological properties of winning and losing plant species and compared observed biotic changes to land‐cover data spatially and temporally matching the regional flora data. Results Winner species were strongly associated with shaded, fertile, well‐drained conditions. Loser species were associated with open, infertile conditions with either moist or xeric soils. The major land‐use changes driving biotic change were: (a) drainage of moist and wet biotopes; (b) active afforestation and passive scrub overgrowth due to ceased grazing; and (c) landscape‐wide increased nutrient availability. However, the magnitude of increase or decrease in the area of a land‐cover type was a poor predictor of the number of habitat‐associated winner or loser species. This suggests that degradation of extant biotopes and/or low quality of new biotopes limits plant species richness, in particular of habitat specialists. Conclusions We demonstrate a displacement of plant ecospace towards mesic, shaded and fertile conditions, with profound effects on plant diversity, and mainly driven by intensified agricultural/silvicultural use of the landscape matrix, which has strongly affected the main plant habitats in scattered semi‐natural fragments. We assessed drivers of change to the regional species pool of plants in a human‐dominated country on the time scale of one and a half century. The winner species were strongly indicative of shady, fertile and well‐drained conditions, while the loser species in contrast were indicative of open, infertile conditions, with either wet or xeric soils.