Coastal habitats shield people and property from sea-level rise and storms

Extreme weather, sea-level rise and degraded coastal ecosystems are placing people and property at greater risk of damage from coastal hazards1–5. The likelihood and magnitude of losses may be reduced by intact reefs and coastal vegetation1, especially when those habitats fringe vulnerable communities and infrastructure. Using five sea-level-rise scenarios, we calculate a hazard index for every 1 km2 of the United States coastline. We use this index to identify the most vulnerable people and property as indicated by being in the upper quartile of hazard for the nation’s coastline. The number of people, poor families, elderly and total value of residential property that are most exposed to hazards can be reduced by half if existing coastal habitats remain fully intact. Coastal habitats defend the greatest number of people and total property value in Florida, New York and California. Our analyses deliver the first national map of risk reduction owing to natural habitats and indicates where conservation and restoration of reefs and vegetation have the greatest potential to protect coastal communities. Globally, coastal flooding and sea level are expected to increase significantly by mid-century, with potentially severe consequences for coastal populations around the world6. In the United States— where 23 of the nation’s 25 most densely populated counties are coastal—the combination of storms and rising seas is already putting valuable property and large numbers of people in harm’s way1–5. The traditional approach to protecting towns and cities has been to ‘harden’ shorelines. Although engineered solutions are necessary and desirable in some contexts, they can be expensive to build and maintain7,8, and construction may impair recreation, enhance erosion, degrade water quality and reduce the production of fisheries9,10. Over the past decade, efforts to protect people and property have broadened11 to consider conservation and restoration of marshes, seagrass beds, coastal and kelp forests, and oyster and coral reefs that buffer coastlines from waves and storm surge12–14 and provide collateral benefits to people15. But approaches and tools for evaluating the potential role of natural defence mechanisms lag behind those for hardening shorelines15. Prioritizing ecosystems for conservation or restoration in service of natural hazard reduction requires knowledge of where habitats are most likely to reduce exposure to erosion and flooding from storms and future sea levels, and protect vulnerable people and property (see Supplementary Information for definitions