The effectiveness of urban green space management on butterfly diversity depends on the species functional groups

Source abstract

Many cities are implementing greening strategies that enhance habitat quality, connectivity, and the extent of urban green spaces aiming to improve biodiversity conservation and ecosystem services. However, these strategies often lack scientific evaluation regarding their effectiveness in promoting biodiversity from a functional perspective. We used butterflies in the city of Barcelona as study system to analyse if/how habitat management, connectivity and site area improved urban functional diversity. Using Bayesian Structural Equation Models, we analysed the effect of the city management practices on the presence and abundance of the urban butterfly functional groups during five years (2020–2024). We also performed a post hoc analysis testing the effect of management on a functional diversity metric (RaoQ), and on the taxonomic and phylogenetic diversity. We evidenced that the reduction of mowing frequency favoured all groups. The positive or negative effect of other management and landscape drivers varied across groups. For example, specialist species with lower dispersal ability and lower reproductive rates were mainly affected by mowing frequency, connectivity and vegetation composition (spontaneous meadows), while generalist dispersive reproductive species were highly affected by site area. The variation in sensitivity across functional groups was not captured by the functional diversity metric alone. Our results provide further evidence of the importance of low management intensity and vegetation composition, promoting native meadows and avoiding grassy lawns, and provide novel evidence on the need to link specific management strategies to specific functional groups (or traits), rather than using global metrics of diversity.