Urbanization is associated with reduced genetic diversity in marine fish populations

The economic and ecological benefits of living by the ocean have led many coastal settlements to grow into large densely populated cities. Large coastal cities have had considerable environmental effects on marine ecosystems through resource extraction, waste disposal, and use for transportation. Thus, it is important to understand the consequences of urbanization and human activities on evolutionary processes and biodiversity in marine fishes. Using published population genetic datasets for marine fishes amounting to 75,496 individuals sampled from 73 species at 1143 sample sites throughout the world’s oceans, we evaluated how human population density and a composite measure of cumulative human impacts affected genetic diversity and differentiation. We found that genetic diversity was significantly lower in marine fish populations associated with denser human populations regardless of species and locality. The effects of cumulative human impacts on genetic diversity were less prominent, perhaps due to this measure capturing more spatially varying processes. Urbanization in coastal regions has degraded marine biodiversity in a way that erodes adaptive potential for marine fish populations. This highlights the need to mitigate threats from human activities and focus efforts on sustainable urban planning and resource use to conserve marine biodiversity sustaining coastal fisheries and ecosystems.