Authors: Ossola, Alessandro; Farrell, Clare;Williams, Nicholas;Leishman, Michelle;

Among threats to global plant diversity, urbanization has been a key driver of species loss and extinction. Trade among urban areas has further fueled the spread of exotic and invasive species, impacting native plant communities globally. New evidence, however, recognizes cities as unexpected repositories of biological diversity. For instance, up to 15% of the global tree flora is estimated to live in the world’s cities. Urban areas contain hundreds of species that are considered either extinct in the wild, critically-endangered, endangered, rare, or vulnerable to extinction. Rather than viewing urban horticulture as a threat to biodiversity, we argue that this practice - alongside the landscape plantings it delivers - have unrealized potential for meaningful plant conservation at large scales. Urban areas have resources, space, technologies and human capacity to sustain plant conservation at the wide scale needed to limit further loss of plant diversity. In this contribution we present a framework and roadmap that seeks a new nature-positive vision for urban horticulture to significantly contribute to the UN’s Decade on Ecosystem Restoration (2021-2030) and UN Sustainable Development Goals 11 Sustainable Cities and Communities, and SDG 15 Life on Land.