Agro-pastoral management drives rapid and directional butterfly community dynamics: Evidence from three decades of high-resolution data

Grasslands are among the most biodiverse ecosystems, but one of the most threatened in the temperate region. While land-use changes, through intensification or abandonment, can rapidly transform these habitats, how grassland-dependent communities respond over time to different management regimes remains poorly understood. We analysed long-term butterfly monitoring data from two contrasting ecological contexts in Catalonia (NE Spain), a coastal agricultural plain undergoing restoration and a montane grassland experiencing intensification. We examined butterfly community composition using ordination, cutting-point detection, turnover and mixed models. Butterfly communities, after correcting for climate, responded rapidly to management transitions, with detectable shifts emerging within one to two years. However, at the coastal site, turnover peaked around transition events, suggesting that community change was driven primarily by episodic disturbance events. In contrast at the montane site, turnover also varied among stable management regimes, reflecting the greater ecological specialisation of the resident butterfly community. Species richness remained stable across management regimes at the coastal site, despite marked compositional turnover, indicating species replacement, but at the montane site it varied, with intensive fodder and high-grazing regimes supporting the lowest diversity values. Extensive grazing combined with mowing regimes promotes the highest functional diversity at both sites. At the montane site, high diversity and functional redundancy may have contributed to maintaining stable community structure despite species turnover, although this may mask vulnerabilities if land use becomes more intensive montane. These findings reinforce the value of long-term butterfly monitoring as an early-warning system for management-driven ecological change, and highlight the conservation importance of heterogeneous, extensively managed grasslands.