Despite decades of work in environmental science and ecology, estimating human influences on ecosystems remains challenging. This is partly due to irreducibly complex chains of causation among ecosystem elements, but the difficulty of collecting biological data at sufficient spatial, temporal, and taxonomic scales exacerbates the problem. Here, we demonstrate the utility of environmental DNA (eDNA) for quantifying associations between human land use and changes in an adjacent ecosystem. We analyze metazoan eDNA sequences from water sampled in nearshore marine eelgrass communities and assess the relationship between these ecological communities and the degree of urbanization in the surrounding watershed.
Results/Conclusions
We find strongly increasing richness and decreasing beta diversity with greater urbanization, and similar trends in the diversity of functional niches with urbanization. Given that different sampling methods necessarily reveal different pictures of an ecosystem, we then discuss the advantages of eDNA—which we used here to detect hundreds of taxa simultaneously—as a complement to traditional ecological sampling, particularly in the context of large-scale ecosystem assessments where exhaustive manual sampling is impractical. Genetic data are a powerful means of uncovering human-ecosystem interactions that might otherwise remain hidden; nevertheless, no sampling method reveals the whole of a biological community.