Butterflies as indicators of restoration success: insights from habitat restoration in agricultural landscapes

Introduction: Conservation strategies to support pollination service in agricultural landscapes increasingly rely on habitat restoration to mitigate biodiversity loss and support pollinator populations. However, the effectiveness of such measures depends on pollinator traits and landscape context. Objectives: This study evaluated the impact of habitat restoration on butterfly (Lepidoptera: Papilionoidea and Hesperioidea) and bumblebee communities (Hymenoptera: Apidae: Bombus spp.), recognized as key pollinator indicators. The research was conducted on nine farms in northern Italy, where restoration efforts focused on establishing pollinator-friendly habitats, including species-rich grasslands and flower strips. Methods: Monitoring was conducted along transects subdivided into restored and unrestored sub-transects. High-resolution land cover data were used to assess landscape composition at both local and landscape scales. Surveys were conducted monthly from May to September, before (2022) and after (2023) restoration. Linear mixed models were used to analyze the effects of the percent cover of restored habitat area and landscape composition on pollinator species richness and abundance. Results: Restoration positively affected pollinator communities, although responses varied between the two pollinator groups. Butterflies showed clear increases in richness and abundance in relation to percent cover of both restored habitat area and land cover/land use types, while bumblebee responses were less marked. A beneficial effect of restoration measures on unrestored areas was observed for butterflies, with higher richness and abundance also in adjacent unrestored areas. Conclusions: The contrasting responses observed between butterflies and bumblebees emphasize the value of butterflies as sensitive bioindicators of habitat restoration success.