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

Study Number:

39

Author:

K. K. Arkema, G. Guannel, G. Verutes, S. A.Wood, A. Guerry, M. Ruckelshaus, P. Kareiva, M. Lacayo & J. M. Silver.

Abstract:

Extreme weather, sea-level rise and degraded coastal ecosystems are placing people and property at greater risk of damage from coastal hazards (climate change) (Day et al. 2007, Shepard et al. 2012, USEPA 2009, Nichollas et al. 1999, Sallenger et al. 2012). The likelihood and magnitude of losses may be reduced by intact reefs and coastal vegetation (Day et al. 2007), 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.

Main Results and Conclusions:

• A model was created to measure the protective role of coastal habitat around the U.S. against storms and sea-level rise (1). The study concluded that “the extent to which natural defense mechanisms operate depends on the relative location of the hazard (for example, sea-level rise hotspots) (Sallenger et al. 2012), habitats, vulnerable populations and properties” (4).
• “Today 16% of the US coastline comprises ‘high hazard’ areas, harbouring 1.3 million people, 250,000 elderly, 30,000 families below the poverty line and US$300 billion in residential property value (Fig. 1)”(2).
• Results from future scenarios show that by the year 2100 “… more coastal segments will be highly exposed to hazards and that the amount of highly threatened people and property will increase by 30-60% over the current scenario (Fig. 1). Given modeled sea-level rise and observed storm characteristics (climate change), 1.7 to 2.1 million of today’s population will live in areas exposed to the highest hazard (Fig. 1). Between 30,000 and 40,000 families below the poverty line and US$400 to US$500 billion of residential property will be most exposed to future hazards (Fig. 1)”(2).
• The study shows that “At present, habitats protect 67% of the coastline, as hazard increases in two-thirds of all segments in the scenario without habitat. Habitat loss would double the extent of coastline highly exposed to storms and sea-level rise (hazard index >3:36), making an additional 1.4 million people now living within 1 km of the coast vulnerable”(2). (Climate Change)
• Some regions around the U.S. are more vulnerable than others, specifically the east and gulf coasts where the coastal habitats are comprised of “softer substrates (for example, beaches, deltas)”, the tidal surges are stronger and the rates of sea-level rise are higher (2). These areas can be protected but substantial coastal forest, wetland and dune habitats are needed to buffer storm impacts.
• Coastal vegetation protects properties that value as low as $0 (Jefferson, Florida) to $20 billion (Stuffolk and Kings, New York) (3).
• In summary, mangroves play a critical role as bioshields: “…if the extensive coral, mangrove and seagrass ecosystems that line Florida at present persist in the face of coastal development and climate change, our analysis predicts these habitats will reduce exposure of nearly US$4 billion worth of 2010 home property values within 1 km of the coastline by 2100 up from US$0.7 billion at present (Fig. 3a,b insets)”(4).

Works Cited:

Day, J. W. et al. 2007. Restoration of the Mississippi Delta: Lessons from Hurricanes Katrina and Rita. Science 315: 1679-1684.

Nicholls, R. J., Hoozemans, F. M. J. and M. Marchand. 1999. Increasing flood risk and wetland losses due to global sea-level rise: Regional and global analyses. Global Environmental Change 9 (Suppl. 1): S69-S87.

Sallenger, A. H., K. S. Doran, and P. A. Howd. 2012. Hotspot of accelerated sea-level rise on the Atlantic coast of North America. Nature Climate Change 2: 884-888.

Shepard, C. et al. 2012. Assessing future risk: Quantifying the effects of sea level rise on storm surge risk for the southern shores of Long Island, New York. Natural Hazards 60: 727-745.

U.S. Environmental Protection Agency (USEPA). 2009. CCSP Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region.