Toward cross-realm management of coastal urban ecosystems

Urbanization and its resulting environmental stressors are often managed within terrestrial, freshwater, or marine realms separately. This is problematic for the many cities situated at the intersection between these realms, because stressors and associated management actions can affect multiple realms simultaneously and impacts may be compounded at boundaries. Here, we describe management approaches operating within and across realms, and identify impediments to cross-realm urban management. We find that management that fails to consider connectivity either within or between realms at best delivers only small-scale benefits and at worst can produce large-scale unintended negative outcomes. In contrast, management that explicitly considers inter-realm connectivity can generate large benefits relative to the cost of interventions. Successful cross-realm management requires consideration of connectivity, scale (temporal and spatial), and ecological processes across more than two realms, and is underpinned by an integrated and collaborative approach that provides multiple benefits.