Non-lethal bumblebee monitoring in high-diversity areas

Among European wild pollinators, bumblebees (Bombus Latreille, 1802) are of particular interest, and many species have shown documented declines in abundance and distribution. Studies have employed both lethal and non-lethal sampling methods, but for species of conservation concern, it is especially important to use approaches that allow research without compromising populations. Developing reliable, non-lethal methods for accurate identification is thus essential. Our first aim was to analyse the status of bumblebee monitoring across Europe through a systematic review. We assessed the spatial and temporal distribution of studies, the methodologies used and the prevalence of lethal versus nonlethal approaches. Our analysis showed that scientific interest in bumblebees increased over time but declined after a peak in 2021, and that research effort is unevenly distributed across European countries, regardless of European Union (EU) membership. Our second aim was to evaluate the feasibility of taxonomically precise, low-impact bumblebee monitoring in species-rich areas to obtain long-term trend data. Therefore, we conducted a field–laboratory identification test in which bumblebees were monitored through standardized transect walks and double-identified in the field and laboratory over 3 years. This allowed us to develop a method for training and assessing operator identification skills, enabling rapid, non-lethal identification. With the implementation of the EU-PoMS mandated under Article 10 of the Nature Restoration Regulation, demand for efficient non-lethal identification will increase. Our method provides a framework for improving operator skills and demonstrates that non-lethal transect sampling is feasible and necessary given declining pollinator populations and the limited uptake of non-lethal approaches in recent research.