Using Unstructured Crowd-sourced Data to Evaluate Urban Tolerance of Terrestrial Native Species within a California Mega-City

In response to biodiversity loss and biotic community homogenization in urbanized landscapes, City managers around the world are increasingly working to conserve and increase urban biodiversity. Accordingly, around the world, previously extirpated species are (re)colonizing and otherwise infiltrating urban landscapes, while once abundant species are in various states of decline. Tracking the occurrence of traditionally urban intolerant species and loss of traditionally urban tolerant species should be a management goal of urban areas, but we generally lack tools to study this phenomenon. To address this, we first used species occurrences from iNaturalist, a large collaborative dataset of species observations, to measure an urban association index (UAI) for 967 native animal species that occur in the city of Los Angeles. On average, the occurrence of native species was negatively associated with our composite measure of urban intensity, with the exception of snails and slugs, which instead occur more frequently in areas of increased urban intensity. Next, we assessed 8,348 0.25 x 0.25 mile grids across the City of Los Angeles to determine the average grid-level UAI scores (i.e., a summary of the UAIs present in a grid cell, which we term Community Urban Tolerance Index or CUTI). We found that areas of higher urban intensity host more urban tolerant species, but also that taxonomic groups differ in their aggregate tolerance of urban areas, and that spatial patterns of tolerance vary between groups (e.g., mammals are not the same as birds). The framework established here was designed to be iteratively reevaluated by city managers of Los Angeles in order to track the progress of initiatives to preserve and encourage urban biodiversity, but can be rescaled to sample different regions within the city or different cities altogether to provide a valuable tool for city managers globally.