Adapting to climate change, does it work? Effects of climate change and adjusted management on biodiversity of roadside grasslands

This research investigates the drivers of biodiversity decline in semi-natural grasslands, particularly Dutch roadside grasslands, and potential management adjustments to mitigate their effects. Analyses of vegetation change (2004-2020) revealed that winter warming, especially under high nitrogen deposition, was a major driver of plant diversity loss and community shifts. Winter warming promoted competitive species, particularly grasses, through extended growing seasons and increased biomass production, disadvantaging non-competitive species, especially forbs. Concurrent shifts in management, in productive sites particularly a reduced mowing frequency, likely further contributed to this decline. In contrast, summer drought events generally reduced the competitive dominance of tall perennial species, creating opportunities for subordinate species. However, benefits were not observed for species of conservation concern and were more short-lived (and thus overall weaker) than the effects of winter warming.

A field experiment applying management adjustments demonstrated that increasing mowing frequency from once to twice per year and delaying the final cut substantially restored plant diversity, vegetation composition, and aboveground biomass to near pre-climate-change levels in productive roadside grasslands. Delayed mowing also enhanced arthropod biomass regardless of site productivity, and the increased mowing frequency supported ground-dwelling arthropods and early-season pollinators in productive roadside grasslands, although mowing created temporary resource gaps, indicating the importance of phased implementation of mowing regimes.

Together, these findings identify winter warming as an overlooked driver of grassland biodiversity loss and demonstrate that altered mowing regimes can effectively counteract its impacts.