Environmental contamination predicts mammal diversity and mesocarnivore activity in the Seattle-Tacoma metro area

Environmental factors influencing the distribution and abundance of wildlife populations in the Anthropocene are increasingly complicated by historical and ongoing industrialization. The legacy of industrialization has enduring impacts on environmental quality, with downstream consequences for wildlife. However, industrial contaminants are not evenly distributed across or within cities, and their effects on free-ranging wildlife at the population and community levels remain poorly understood. We investigated whether environmental contaminant risk from pollutants was associated with mammalian diversity and carnivore activity in the Seattle-Tacoma metropolitan area, Washington, USA. Using camera trap data collected across 74 sites, we modeled environmental contaminant risk, natural land cover, and human population density against several mammal community metrics and against detections of carnivore species. Environmental contaminant risk was measured based on proximity to contaminated industrial and residential sites, using publicly available indices. We found that mammalian diversity and evenness decreased as contaminant risk increased, especially in Seattle. Across the metro area and within Seattle, coyote (Canis latrans) activity was negatively associated with contaminant risk, while raccoon (Procyon lotor) activity was positively associated with contaminant risk; opossums (Didelphis virginiana) showed no response. Within Tacoma, contaminant risk was not significantly associated with mammal community metrics or carnivore activity, but human population density had a negative influence on coyote activity and a positive influence on opossum activity. Our results highlight the potential impacts of industrialization in ecological processes, and the need for species- and city-specific approaches in understanding the role they play in shaping urban wildlife communities. Ecological studies that incorporate these impacts can inform urban planning and conservation strategies that improve environmental quality for urban wildlife populations.