A human impact metric for coastal ecosystems with application to seagrass beds in Atlantic Canada

Coastal biogenic habitats are particularly vulnerable to cumulative human impacts from both terrestrial and marine realms. Yet the broad spatial scale used in current global or regional approaches of quantifying multiple anthropogenic stressors are not relevant to the local or bay-wide scales affecting most coastal biogenic habitats. To fill this gap, we developed a standardized human impact metric to quantify the magnitude of anthropogenic impacts to coastal ecosystems more broadly, and biogenic habitats in particular. We applied this metric to 180 seagrass beds ( Zostera marina ), an important biogenic habitat prioritized for marine protection, across Atlantic Canada. Our impact metric includes five bay-scale and four local-scale terrestrial and marine-based impacts. Results show that seagrass beds and coastal bays in Atlantic Canada exist across a wide gradient of human impacts. Considerable differences in the range and intensity of impacts within and between regions provide insight into where coastal bays and seagrass ecosystems are expected to be most and least affected by individual or cumulative human threats. We discuss implications for management and conservation planning, and the general application of our impact metric to other coastal regions and habitats in Canada and beyond.