Federal Coordinating Lead Authors:
Jeffrey Payne, National Oceanic and Atmospheric Administration
William V. Sweet, National Oceanic and Atmospheric Administration
Chapter Lead:
Elizabeth Fleming, U.S. Army Corps of Engineers
Chapter Authors:
Michael Craghan, U.S. Environmental Protection Agency
John Haines, U.S. Geological Survey
Juliette Finzi Hart, U.S. Geological Survey
Heidi Stiller, National Oceanic and Atmospheric Administration
Ariana Sutton-Grier, National Oceanic and Atmospheric Administration
Review Editor:
Michael Kruk, ERT, Inc.
USGCRP Coordinators:
Matthew Dzaugis, Program Coordinator
Christopher W. Avery, Senior Manager
Allyza Lustig, Program Coordinator
Fredric Lipschultz, Senior Scientist and Regional Coordinator

Coastal Effects

The Coasts chapter of the Third National Climate Assessment, published in 2014, focused on coastal lifelines at risk, economic disruption, uneven social vulnerability, and vulnerable ecosystems. This Coastal Effects chapter of the Fourth National Climate Assessment updates those themes, with a focus on integrating the socioeconomic and environmental impacts and consequences of a changing climate. Specifically, the chapter builds on the threat of rising sea levels exacerbating tidal and storm surge flooding, the state of coastal ecosystems, and the treatment of social vulnerability by introducing the implications for social equity.

U.S. coasts are dynamic environments and economically vibrant places to live and work. As of 2013, coastal shoreline counties were home to 133.2 million people, or 42% of the population.1 The coasts are economic engines that support jobs in defense, fishing, transportation, and tourism industries; contribute substantially to the U.S. gross domestic product;1 and serve as hubs of commerce, with seaports connecting the country with global trading partners.2 Coasts are home to diverse ecosystems such as beaches, intertidal zones, reefs, seagrasses, salt marshes, estuaries, and deltas3,4,5 that support a range of important services including fisheries, recreation, and coastal storm protection. U.S. coasts span three oceans, as well as the Gulf of Mexico, the Great Lakes, and Pacific and Caribbean islands.

The social, economic, and environmental systems along the coasts are being affected by climate change. Threats from sea level rise (SLR) are exacerbated by dynamic processes such as high tide and storm surge flooding (Ch. 19: Southeast, KM 2),6,7,8 erosion (Ch. 26: Alaska, KM 2),9 waves and their effects,10,11,12,13 saltwater intrusion into coastal aquifers and elevated groundwater tables (Ch. 27: Hawaiʻi & Pacific Islands, KM 1; Ch. 3: Water, KM 1),14,15,16,17 local rainfall (Ch. 3: Water, KM 1),18 river runoff (Ch. 3: Water, KM 1),19,20 increasing water and surface air temperatures (Ch. 9: Oceans, KM 3),21,22 and ocean acidification (see Ch. 2: Climate, KM 3 and Ch. 9: Oceans, KM 1, 2, and 3 for more information on ocean acidification, hypoxia, and ocean warming).23,24

Although storms, floods, and erosion have always been hazards, in combination with rising sea levels they now threaten approximately $1 trillion in national wealth held in coastal real estate25 and the continued viability of coastal communities that depend on coastal water, land, and other resources for economic health and cultural integrity (Ch. 15: Tribes, KM 1 and 2).

Impacts of the 2017 Hurricane Season

Quintana Perez dumps water from a cooler into floodwaters in the aftermath of Hurricane Irma in Immokalee, Florida. Photo credit: AP Photo/Gerald Herbert.

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