Landscape‐scale differences among cities alter common species’ responses to urbanization

Abstract

Understanding how biodiversity responds to urbanization is challenging, due in part to the single‐city focus of most urban ecological research. Here, we delineate continent‐scale patterns in urban species assemblages by leveraging data from a multi‐city camera trap survey and quantify how differences in greenspace availability and average housing density among 10 North American cities relate to the distribution of eight widespread North American mammals. To do so, we deployed camera traps at 569 sites across these ten cities between 18 June and 14 August. Most data came from 2017, though some cities contributed 2016 or 2018 data if it was available. We found that the magnitude and direction of most species' responses to urbanization within a city were associated with landscape‐scale differences among cities. For example, eastern gray squirrel (Sciurus carolinensis), fox squirrel (Sciurus niger), and red fox (Vulpes vulpes) responses to urbanization changed from negative to positive once the proportion of green space within a city was >~20%. Likewise, raccoon (Procyon lotor) and Virginia opossum (Didelphis virginiana) responses to urbanization changed from positive to negative once the average housing density of a city exceeded about 700 housing units/km2. We also found that local species richness within cities consistently declined with urbanization in only the more densely developed cities (>~700 housing units/km2). Given our results, it may therefore be possible to design cities to better support biodiversity and reduce the negative influence of urbanization on wildlife by, for example, increasing the amount of green space within a city. Additionally, it may be most important for densely populated cities to find innovative solutions to bolster wildlife resilience because they were the most likely to observe diversity losses of common urban species.

Parallel evolution of urban-rural clines in melanism in a widespread mammal

“…2) did not support our prediction that forest cover facilitates gene flow and weakens clines along the urbanization gradient. Gray squirrels require trees, and squirrel abundance and distribution along urbanization gradients is limited by greenspace availability, particularly in large cities 35 . It is possible that cities with more extensive forest cover support a greater abundance of gray squirrels, increasing effective population size and thereby making selection more efficient in overcoming the effects of genetic drift on morph frequencies.…”

Wealth and urbanization shape medium and large terrestrial mammal communities

“…Likewise, as mammal species richness at the local scale typically decreases with urban intensity (Fidino et al, 2020;Ordeñana et al, 2010), we sought to assess the strength of this relationship across multiple cities. To quantify these relationships, we used a Bayesian multi-city, multi-species occupancy model which estimates species richness along and species-specific responses to environmental gradients (Sutherland et al, 2016).…”

Downtown Diet: a global meta-analysis of urbanization on consumption patterns of vertebrate predators

“…The effects of such varied mechanisms induced from urbanization manifest differently among taxonomic groups with wildlife responses being scale-dependent (Fidino et al, 2020). For example, cities exhibit extreme temperature gradients, which could result in varied consumptive patterns, as low temperatures increased attack rate in Daphnia, while higher temperatures increased the prey consumption rate in reptiles and birds (Wasserman et al, 2016;Scott et al, 2017).…”