Urbanization alters sandy beach scavenging assemblages but not ecosystem function

Abstract

Urbanization is rapidly transforming coastal landscapes around the world, altering the structure and function of marine, intertidal, and terrestrial ecosystems. In this study, we explore the impact of urbanization on the structure of vertebrate scavenging assemblages and the ecosystem functions they provide in sandy beach ecosystems across 40km of the central California coast, USA. We surveyed vertebrate scavenging assemblages using baited camera traps on 17 beaches spanning a gradient of coastal urbanization. We found that urbanization extent within small spatial scales (i.e., 1km or 3km radii of each site) and the rate of beach visitation by humans or domestic dogs were the best additive predictors of assemblage structure. We identified pronounced urbanization-associated shifts in the composition of vertebrate scavenger guilds but found that that these differences did not lead to subsequent changes in ecosystem functions performed by shoreline scavengers. Rates of carrion processing did not differ across the urbanization gradient, with synanthropic and non-native species compensating for the absence of the predominate native scavengers documented in rural areas. Our results underscore the pervasive and nuanced effects of urbanization on the dynamics of land-sea connectivity and demonstrate that urban ecosystems can sometimes sustain critical ecosystem functions in the face of landscape transformation. Recognizing the intricate interplay between urbanization and shoreline ecosystem dynamics, we suggest comprehensive consideration of cross-realm impacts in ongoing conservation and development efforts to ensure the sustainability and resilience of urban land- and seascapes.