Understanding and managing human threats to the coastal marine environment.

Coastal marine habitats at the interface of land and sea are subject to threats from human activities in both realms. Researchers have attempted to quantify how these various threats impact different coastal ecosystems, and more recently have focused on understanding the cumulative impact from multiple threats. Here, the top threats to coastal marine ecosystems and recent efforts to understand their relative importance, ecosystem-level impacts, cumulative effects, and how they can best be managed and mitigated, are briefly reviewed. Results of threat analysis and rankings will differ depending on the conservation target (e.g., vulnerable species, pristine ecosystems, mitigatable threats), scale of interest (local, regional, or global), whether externalities are considered, and the types of management tools available (e.g., marine-protected areas versus ecosystem-based management). Considering the cumulative effect of multiple threats has only just begun and depends on spatial analysis to predict overlapping threats and a better understanding of multiple-stressor effects and interactions. Emerging conservation practices that hold substantial promise for protecting coastal marine systems include multisector approaches, such as ecosystem-based management (EBM), that account for ecosystem service valuation; comprehensive spatial management, such as ocean zoning; and regulatory mechanisms that encourage or require cross-sector goal setting and evaluation. In all cases, these efforts require a combination of public and private initiatives for success. The state of our ecological understanding, public awareness, and policy initiatives make the time ripe for advancing coastal marine management and improving our stewardship of coastal and marine ecosystems.