From cities to refuges for pollinators: Urban practices for enhancing pollinator habitats in changing landscapes

Urban built-up lands and their expansion significantly reduce green areas, where pollinators should find flowers for feeding and places for nesting, threatening their existence. Reversing the decline of pollinators is a global goal, as they are a multi-taxa guild linked to essential ecosystem services and they sustain ecosystem functioning. We aimed to highlight the frontier of pollinator support, by evaluating emerging practices to improve the biodiversity of pollinators in urban contexts, that could integrate consolidated actions already in use. We also clarified the essential role of society in this context and the research gaps. For pollinators in urban areas, it is crucial to provide adequate nutrition and nesting substrates. This can be achieved by valorising the existing resources, tuning pollinator-friendly management (e.g., deadwood, no mowing) and also providing human-made solutions. Nutritional resources should assure sown flower survival across years and integrate ornamental plants to fill gaps in blooming phenology and rewards quality. Stimulating oviposition and adding flower arrangements on small surfaces are promising ways, but more testing of new applications and with neglected to map pollinators is needed. It is also necessary to engage the society with dedicated policies and to map pollinators for area prioritization, while counteract unwillingness with educational campaigns and citizen science. The ensemble of these aspects contributes to a framework for enhancing pollinator habitats in urban areas. Synthesis and applications. A framework for the support of pollinators in urban areas is developed, based on five pillars: nesting, flower resources, artificial supplements, management and society acceptance, with additional key elements contributing from science and society. Administrators should incorporate strategies for pollinators based on this framework by means of co-planning with stakeholders, including expert scientists, hence paving the way to more coherent and efficient ways to improve and restore pollinator biodiversity in challenging landscapes.