Can macroplastics affect riparian vegetation blooming and pollination? First observations from a temperate South-European river

Since plastics are a global growing concern that persists in nature, they threaten ecosystem conservation and human health. Particularly, pollination is one of the most important ecological services being pivotal to the ecosystem's long-term functioning and human welfare. However, pollination is threatened by pesticides, urbanisation, habitat loss, and contaminants. As interactions between plastics and biota or ecosystem service remain neglected, the major challenge would be to research it. Our achievement was a first attempt to assess the effects of macroplastics on riparian vegetation and the ecosystem service of pollination. Here, (i) while investigating macroplastics entrapped by riparian vegetation, (ii) we propose the new field observation of the flower's coverage by macroplastics. Then, (iii) we indirectly assessed the possible interaction between macroplastic litter and the ecosystem service of pollination. Finally, (iv) we performed a meta-analysis search to understand better how many studies were carried out on this topic. To achieve our aim, surveys of riverine macroplastic litter entrapped in riparian vegetation were carried out in the urban tract of the Aniene River. To assess if pollination was possibly reduced by macroplastics covering flowers, we observed the visitation of pollinators on flowers. Overall, we observed that flowers of riparian vegetation were covered by macroplastics, preventing them from being pollinated by insects, and pollination success (i.e., successful pollination) was potentially reduced to 81.4% by a factor of 18.6%. Our research highlights that macroplastics on vegetation indicate a new stress to plant reproduction, reducing blooming (i.e., flowering or flower production) and pollination. These recent observations urge new studies to evaluate how macroplastic litter accumulates and might affect ecosystem services in long-term research. Our findings could be of particular concern as pollination in agricultural crops and riverine habitats is central to human welfare as an ecosystem service. Considering that most global food crops depend on pollination by insects, crops and fruits (e.g., coffee, cocoa, apples) would not be present without the essential ecosystem service of pollination. Our findings highlight for the first time a new threat (i.e., macroplastic litter) to the blooming with possible implications for the pollination process.