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Rapid urbanization and the global loss of biodiversity necessitate the development of a research agenda that addresses knowledge gaps in urban ecology that will inform policy, management, and conservation. To advance this goal, we present six topics to pursue in urban biodiversity research: the socioeconomic and social–ecological drivers of biodiversity loss versus gain of biodiversity; the response of biodiversity to technological change; biodiversity–ecosystem service relationships; urban areas as refugia for biodiversity; spatiotemporal dynamics of species, community changes, and underlying processes; and ecological networks. We discuss overarching considerations and offer a set of questions to inspire and support urban biodiversity research. In parallel, we advocate for communication and collaboration across many fields and disciplines in order to build capacity for urban biodiversity research, education, and practice. Taken together we note that urban areas will play an important role in addressing the global extinction crisis.

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In cities, naturally regenerating plant populations are critical in sustaining both ecological function and ecosystem services. However, scientists have a limited understanding of the urban ecosystem conditions and stressors that influence basic life‐history processes and constraints for plant populations. Here, we synthesize current research on the recruitment dynamics of urban plants (processes associated with adding individuals to populations) and present a conceptual framework for urban recruitment limitation. From grasslands to forests, and from natural to constructed habitats, multiple urban drivers – including climate, land‐cover change, pollution, and biotic invasions – affect plant recruitment. These drivers often interact, and their effects are frequently species‐, habitat‐, or region‐specific. Furthering a “mechanistic” understanding (one that focuses on the underlying ecological mechanisms of observed phenomena) of how these drivers alter plant population dynamics will improve the conservation, management, and restoration of urban greenspaces.

Urban forested natural areas are valuable ecological and social resources, but long‐term sustainability of these habitats is challenged by environmental and social factors associated with urban ecosystems. Advances in city‐scale assessments of urban forests have increased the resolution of forest community types and conditions, allowing for improved understanding of ecological function, such as natural regeneration, in these urban habitats. By applying metrics of tree regeneration that are commonly used for the management of rural forests, urban ecologists can test the potential for traditional forest management strategies within our cities. In this study, we compare urban and rural oak–hickory forest composition and structure and the capacity for natural regeneration in the New York metropolitan area. Specifically, we use two metrics of advance regeneration that describe the abundance of seedlings and saplings at different size classes to test whether this management for natural regeneration is a viable option. We found differences in recruitment dynamics between urban and rural forests that have implications for the sustainability of these forests and new management strategies. First, after controlling for forest community type, species composition in urban and rural sites was significantly different across multiple strata and within the seed bank. Species‐specific capacity for natural regeneration was different in urban and rural sites, signaling the possibility of divergent successional trajectories. Second, while differences in species composition exist, both urban and rural sites were dominated by native species across all forest strata except for urban seed banks. Third, despite finding significantly lower average annual seedling abundance in urban (1.9 seedlings/m2) compared to rural (7.1 seedlings/m2) sites, we observed greater density of saplings in urban forests, and no significant difference in stocking index between sites. These findings suggest that early‐establishment barriers to recruitment are greater in urban forest sites. However, once established, seedling transition into advance regeneration stages may not be different between site types, and advance regeneration may, in some cases, be more viable in urban forested natural areas. These results highlight functional differences between urban and rural forest recruitment dynamics that may impact on the future community composition of oak–hickory forests in the two landscape settings.

Cities worldwide are engaging in large-scale greening projects motivated by the wide range of documented ecological, economic, and social benefits of urban forests. Urban forested natural areas are a critical component of the total urban forest but are often overlooked and typically lack formal management frameworks. One approach to addressing this deficiency may be to borrow from traditional ecological management frameworks and practices (that is, silviculture). Although urban forested natural areas share similarities with rural forests, the impacts of urbanization on forest stand dynamics may require modification of these methods and in some cases development of novel silvicultural guidelines. We present an urban silviculture framework through which we synthesize emerging research and identify challenges and opportunities for advancing goal setting, assessments, and on-theground management strategies. Adapting silvicultural practices to cities can improve the long-term sustainability of urban forests and establish management approaches that address future conditions in forests across the urban-rural continuum.

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