OOS 49-1 - The great urban shift: climate change is predicted to drive mass species turnover in cities

Background/Question/Methods
Nature is an integral element of cities globally. Urban green spaces provide many ecosystem services, such as stormwater management, urban heat island mitigation, recreation, and mental wellness support. For many urban dwellers, the wildlife experienced in their city represents the only species with which they have real-life familiarity. However, the species currently found in cities are not permanent fixtures, and anthropogenic impacts such as climate change, could threaten their presence and generational experience with them. By modelling the distribution of over 2000 species in 60 North American cities, we tested whether there is evidence of an impending “great urban shift” where contemporary urban biodiversity will be lost with climate change. Using MaxEnt, we used over 260 million occurrence records to model the current and future range of these species in the next 50 years (2080) under three different greenhouse gas concentration scenarios (SSPs).

Results/Conclusions
Across all species and cities, we found a net-negative change in predicted occurrence, supporting evidence of a great urban shift occurring in North America. A variety of predicted responses were seen across individual cities and regions, with cities along the west coast and in the Great Lakes Region having the largest decline. Interestingly, cities in the American south-west had a predicted increase in contemporary species. Not all species were equally affected, with amphibians, waterfowl, and true bugs (Hemipterans) being the taxa predicted to have the largest declines. The predicted changes in contemporary urban species were consistent across scenarios of greenhouse gas emissions, but our results show that the severity of change will be defined by the magnitude of action on mitigate climate change. We provide the first evidence of a potential great urban shift occurring in cities as climate change alters the composition of urban species. Our work demonstrates a massive change in urban biodiversity that will impact the cultural identity of human residents and potentially the delivery of ecosystem services.