A functional ecological understanding of urban wild bee communities is of growing importance especially in regard to biodiversity conservation, ecosystem service maintenance and effective conservation programmes. In this paper, we review and summarize the published literature aiming to inform future research investigations in the growing field of wild bee functional ecology. Specifically, we: (1) review which functional trait-based analyses have been carried out on wild bees in cities thus far; (2) summarize which wild bee species traits have been considered; (3) evaluate any consistent wild bee trait–environment relationships (i.e. urbanization) across studies; and (4) synthesize findings and limitations to inform future research recommendations. We reviewed 48 studies based on a systematic Web of Knowledge search. We found consistent trait characteristics for ‘nesting type’, ‘diet’, ‘body size’, ‘sociality’ and ‘phenology’ across studies. More than one third of the studies were descriptive and the majority of studies were located in urban gardens in temperate Europe and North America, calling for more research from underrepresented geographic regions and from the entire spectrum of urban habitat types. Of these studies, only five analyzed functional diversity indices and three studies applied statistics to relate urban wild bee traits to urbanization factors. Future studies should consider trait-based statistics, and could incorporate functional trait-based ecological networks to examine network shifts across urbanization gradients. Our review suggests that we lack generalizable information about wild bee trait and urbanization relationships yet, making conservation recommendations challenging. Therefore, we propose more research that considers methodological recommendations to develop a comparable and comprehensive understanding of how urbanization affects the functional ecology of urban wild bees to link with specific urban conservation measures.

Urban social–ecological–technological systems (SETS) are dynamic and respond to climate pressures. Change involves alterations to land and resource management, social organization, infrastructure, and design. Research often focuses on how climate change impacts urban SETS or on the characteristics of urban SETS that promote climate resilience. Yet passive approaches to urban climate change adaptation may disregard active SETS change by urban residents, planners, and policymakers that could be opportunities for adaptation. Here, we use evidence of urban social, ecological, and technological change to address how SETS change opens windows of opportunity to improve climate change adaptation.

The evidence base for the benefits of urban nature for people and biodiversity is strong. However, cities are diverse and the social and environmental contexts of cities are likely to influence the observed effects of urban nature, and the application of evidence to differing contexts. To explore biases in the evidence base for the effects of urban nature, we text-matched city names in the abstracts and affiliations of 14 786 journal articles, from separate searches for articles on urban biodiversity, the health and wellbeing impacts of urban nature, and on urban ecosystem services. City names were found in 51% of article abstracts and 92% of affiliations. Most large cities were studied many times over, while only a small proportion of small cities were studied once or twice. Almost half the cities studied also had an author with an affiliation from that city. Most studies were from large developed cities, with relatively few studies from Africa and South America in particular. These biases mean the evidence base for the effects of urban nature on people and on biodiversity does not adequately represent the lived experience of the 41% of the world’s urban population who live in small cities, nor the residents of the many rapidly urbanising areas of the developing world. Care should be taken when extrapolating research findings from large global cities to smaller cities and cities in the developing world. Future research should encourage research design focussed on answering research questions rather than city selection by convenience, disentangle the role of city size from measures of urban intensity (such as population density or impervious surface cover), avoid gross urban-rural dualisms, and better contextualise existing research across social and environmental contexts.