Organic pesticide spatial and temporal variations in wildflowers – the role of plant diversity and the risk for wild pollinators in protected areas

The widespread use of synthetic phytosanitary products poses serious threats to wild pollinator communities even outside of the agroecosystems where they are primarily used, especially when potential sources spatially coexist with areas whose primary goal is the protection of biodiversity and of ecological integrity. Funded by the “Cilento, Vallo di Diano e Alburni” National Park (Italy), this study was carried out to assess the ecotoxicological risk to wild pollinators posed by the contamination of wild plants with pesticide residues. To this end, and to overcome the limitations of the standard methods relying on honeybees, we embraced an approach focused on evaluating the variations in space and time in the contamination of the diverse species forming entomophilous plant communities. Specifically, the study encompassed 3 monthly field campaigns (April, May, June 2024) in 6 sites of the Park differing in land use, where floristic surveys were carried out. Here, samples of flowers from all the species with sufficient abundance were collected for the analysis of 375 pesticides in pollen and corollas, using a purposely optimized QuEChERS extraction and coupled GC-MS/LC-MS quantification. To better understand the contamination patterns, the functional diversity of plant communities was also evaluated in terms of morphological traits mediating the interaction with pollinators, and biochemical traits, including non-structural carbohydrates, lipids and proteins. Overall, 45 species were studied revealing the use of a few compounds, even in remote areas, potentially targeting different pollinator groups with non-lethal and lethal effects at the measured concentrations. The adopted approach proved particularly effective in tracking contamination even from traditional small-scale agriculture and in rural and remote areas. As a long-term monitoring strategy, it may provide valuable insights for precise ecotoxicological risk assessments of wild pollinators and for the planning of conservation and management actions in protected areas.