City sicker? A meta-analysis of wildlife health and urbanization

Frontiers in Ecology and the Environment

Summary by: Jessica Wenclawiak

How has urbanization affected wildlife health? As cities become more common, this question has become increasingly relevant. Urban areas can interfere with a species’ range, food sources, and interactions, which impacts their health. A group of scientists that included CEID members Cecilia Sánchez and Daniel Becker conducted a meta-analysis of published studies that examined the relationship between urbanization and wildlife health. The meta-analysis focused on five taxonomic groups: herpetofauna, fish, invertebrates, birds, and mammals.

To evaluate the effects of urbanization, the meta-analysis concentrated on studies that measured body condition, parasitism, stress, or toxicants. Various statistical models compared the results of the studies and determined which of the four metrics were most effective at predicting wildlife health in cities. Overall, there was a small negative correlation between urbanization and health. Urban areas showed higher levels of parasitism and toxicants, and neither body condition nor stress differed significantly between urban and non-urban habitats. The aggregation of individuals in cities facilitates the transmission of parasites through close contact, and toxicants can bioaccumulate through the food web. The best predictors of health in urban areas were parasitism and the taxonomic group of the study species.

In addition to examining the results of the studies, the meta-analysis also revealed biases in both the study countries and species. The majority of research occurred in North America and Europe; studying in developing areas would illustrate how rapid urbanization impacts wildlife differently than established cities. Among the five taxonomic groups, herpetofauna and invertebrates were the least studied. Both appeared to be particularly vulnerable to toxicants, so additional research would help protect their health and biodiversity. By studying more species in a greater variety of cities, scientists can create more effective conservation measures for urban wildlife.

Murray, M.H., et al. (2019). City sicker? A meta-analysis of wildlife health and urbanization. Frontiers in Ecology and the Environment, 17(10).