Coastal Areas Impacts & Adaptation

Climate Impacts on Coastal Areas

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The National Oceanic and Atmospheric Administration (NOAA) projects that sea level rise will increase flooding in Charleston, South Carolina. Source: NOAA Coastal Services Center (2012)

The coastline of the United States is highly populated. ^[1] Of the 25 most densely populated U.S. counties, 23 are along a coast. ^[1] Coastal and ocean activities, such as marine transportation of goods, offshore energy drilling, resource extraction, fish cultivation, recreation, and tourism are integral to the nation's economy. ^[2] Coastal areas are also home to species and habitats that provide many benefits to society and natural ecosystems.

Climate change could affect coastal areas in a variety of ways. Coasts are sensitive to sea level rise, changes in the frequency and intensity of storms, increases in precipitation, and warmer ocean temperatures. In addition, rising atmospheric concentrations of carbon dioxide (CO₂) are causing the oceans to absorb more of the gas and become more acidic. This rising acidity could have significant impacts on coastal and marine ecosystems.

The impacts of climate change are likely to worsen many problems that coastal areas already face. Shoreline erosion, coastal flooding, and water pollution affect man-made infrastructure and coastal ecosystems. Confronting existing challenges is already a concern. Addressing the additional stress of climate change may require new approaches to managing land, water, waste, and ecosystems.

To learn about how natural resource managers are helping coastal areas adapt to climate change, please visit the Coasts Adaptation section.

Impacts of Sea Level Rise

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Observed changes in sea level relative to land elevation in the United States between 1958 and 2008. Source: USGCRP (2009)

During the 20th century, global sea level rose by roughly seven inches. ^[3]

In a particular location, the change in sea level that is observed will be affected by the increase in global sea level as well as land movement up or down. The motion of land can be caused by melting ice or tectonic movement. The terms "local" or "relative" sea level refer to both the global change in sea level and the effects of land motion.

Where the land mass is sinking, relative sea level rise rate is larger than the global rate. Some of the fastest rates of relative sea level rise in the United States are occurring in areas where the land is sinking (or “subsiding”), including parts of the Gulf Coast. For example, coastal Louisiana has seen its relative sea level rise by eight inches or more in the last 50 years, ^[2] which is slightly faster than twice the global rate. Subsiding land in the Chesapeake Bay area is also projected to worsen the effects of relative sea level rise, increasing the risk of flooding in cities, inhabited islands, and tidal wetlands. ^[2]

Due to differences in land motion, estimates of future relative sea level rise vary for different regions. Climate change models project that global sea level rise will accelerate in the 21st century. Models based on thermal expansion and ice melt estimate that global sea levels will rise approximately 20 to 39 inches by the end of the century. However, due to uncertainties about the response of ice sheets to warmer temperatures and future emissions of greenhouse gases, higher values are possible and cannot be excluded. ^[4]

For more information on recent and future sea level rise, please visit the Science section.

Growing populations and development along the coasts increase the vulnerability of coastal ecosystems to sea level rise. Development can change the amount of sediment delivered to coastal areas, worsen erosion, and remove or damage wetlands. For example, coastal Louisiana lost 1,900 square miles of wetlands in recent decades due to human alterations of the Mississippi River's sediment system and oil and water extraction that has caused land to sink. As a result of these changes, wetlands do not receive enough sediment to keep up with the rising seas and no longer function as natural buffers to flooding. ^[5]

Rising sea levels could also increase the salinity of ground water and push salt water further upstream. This salinity may make water undrinkable without desalination, and harms aquatic plants and animals that cannot tolerate increased salinity. ^[3] In the mid-Atlantic region, sea level rise is making estuaries more salty, threatening aquatic plants and animals that are sensitive to salinity. ^[2]

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Impacts of Changes in Storm Surge and Precipitation

Coastal areas are also vulnerable to increases in the intensity of storm surge and heavy precipitation. Storm surges already flood low-lying areas, damage property, disrupt transportation systems, destroy habitat, and threaten human health and safety. Sea level rise could magnify the impacts of storms by raising the water level that storm surges affect. ^[6] For example, with projected rates in sea level rise, areas of New York City (portions of lower Manhattan and the southwest shores of Brooklyn, Queens, and Staten Island) could be flooded by several feet of water during strong storms. ^{[3] [7]}

Climate change will likely bring heavier rainfall and more precipitation to some coastal areas. This could lead to increases in runoff and flooding. In addition, warmer temperatures in mountain areas could lead to more spring runoff due to melting of snow. In turn, increases in spring runoff may also threaten the health and quality of coastal waters. Some coastal areas, such as the Gulf of Mexico and the Chesapeake Bay, are already experiencing "dead zones"--areas where bottom water is depleted of oxygen because of pollution from agricultural fertilizers, delivered by runoff. As increases in spring runoff bring more nitrogen, phosphorus, and other pollutants into coastal waters, many aquatic species could be threatened. ^[2]

Decreases in precipitation could also affect the salinity of coastal waters. Droughts reduce fresh water input into tidal rivers and bays, which raises salinity in estuaries, and enables salt water to mix farther upstream. ^[1]

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Impacts of Coastal Water Temperature

Coastal waters have warmed during the last century, and are very likely to continue to warm by as much as 4 to 8°F in the 21st century. ^[2] This warming may lead to big changes in coastal ecosystems, affecting species that inhabit these areas.

Warming coastal waters may cause suitable habitats of temperature-sensitive species to shift northward. Some areas have already seen range shifts in both warm- and cold-water fish and other marine species. Pollock, halibut, rock sole, and snow crab in Alaska and mangrove trees in Florida are a few of the species whose habitats have already begun to shift. ^{[2] [3]} Suitable habitats of other species may also shift because they cannot compete for limited resources with the southern species that are moving northward. ^[2] Invasive species that had not been able to establish populations in colder environments may now be able to survive and start competing with native species. ^[2]

For more information on climate change impacts on species, visit the Ecosystems page.

Climate Ready Estuaries Program

Estuaries are particularly sensitive to many projected impacts of climate change, including erosion from rising seas, changes in storms frequency and intensity, and the amount of precipitation. EPA's Climate Ready Estuaries program works with National Estuary Programs and other coastal managers to:

• Assess climate change vulnerabilities.
• Engage and educate stakeholders.
• Develop and implement adaptation strategies.
• Share lessons learned with other coastal managers.

The Climate Ready Estuaries website provides resources for estuaries and coastal programs that are interested in learning more about climate change impacts and adaptation.

To learn more about estuaries, visit the EPA Estuaries and Coastal Watersheds web page.

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Impacts of Ocean Acidification

Bleached brain coral. Source: NOAA

Higher sea surface temperatures and ocean acidification would increase the risks of coral bleaching events that can lead to loss of critical habitat. ^[2] The rising concentration of carbon dioxide (CO₂) in the atmosphere has increased the absorption of CO₂ in the ocean, where a chemical reaction that reduces the pH and makes the oceans more acidic occurs. This trend will likely continue in the coming decades. A more acidic ocean would adversely affect the health of many marine species, including plankton, mollusks, and other shellfish. In particular, corals can be very sensitive to rising acidity, as it is difficult for them to create and maintain the skeletal structures needed for their support and protection. Corals in the Florida Keys, Hawaii, Puerto Rico, and other U.S. territories could be lost if CO₂ concentrations in the atmosphere continue to rise at their current rate. ^[2]

Learn more about how we can adapt to the coastal impacts of climate change.

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References

1. CCSP (2009). Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region . A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Titus, J.G. (Coordinating Lead Author), K.E Anderson, D.R. Cahoon, D.B. Gesch, S.K. Gill, B.T. Gutierrez, E.R. Thieler, and S.J. Williams (Lead Authors). U.S. Environmental Protection Agency, Washington, DC, USA.

2. USGCRP (2009). Global Climate Change Impacts in the United States . Karl, T.R., J.M. Melillo, and T.C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.

3. Nicholls, R.J., P.P. Wong, V.R. Burkett, J.O. Codignotto, J.E. Hay, R.F. McLean, S. Ragoonaden and C.D. Woodroffe (2007). Coastal systems and low-lying areas. In: Climate Change 2007: Impacts, Adaptation, and Vulnerability . Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds.). Cambridge University Press, Cambridge, United Kingdom.

4. NRC (2011). Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia . National Research Council. The National Academies Press, Washington, DC, USA.

5. CCSP (2008). Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Savonis, M. J., V.R. Burkett, and J.R. Potter (eds.). Department of Transportation, Washington, DC, USA, 445 pp.

6. NRC (2010). Adapting to the Impacts of Climate Change . National Research Council. The National Academies Press, Washington, DC, USA.

7. Field, C.B., L.D. Mortsch, M. Brklacich, D.L. Forbes, P. Kovacs, J.A. Patz, S.W. Running and M.J. Scott (2007). North America. In: Climate Change 2007: Impacts, Adaptation and Vulnerability . Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson (eds.). Cambridge University Press, Cambridge, United Kingdom.

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Adaptation Examples in Coasts

Climate change will likely have significant impacts on coastal communities and marine ecosystems. Accelerated erosion, sea level rise, salt water intrusion (where water supplies become more saline), stronger storms, and warmer ocean temperatures are likely to disturb sensitive marine ecosystems and damage private property and public infrastructure throughout the U.S. coastal zone. To learn more about how climate change can impact coasts, visit the impacts section of the Coastal Impacts & Adaptation page.

Many coastal states and communities are taking actions to prepare for and adapt to the impacts of climate change. Coastal adaptation measures ^[1] include a wide variety of activities that include:

• Restoring natural storm surge buffers and incorporating climate change into coastal habitat restoration plans
• Building or repairing dikes, seawalls, and other structures that protect cities from erosion and storms
• Modifying building codes to enable structures to withstand higher water levels
• Expanding setbacks (the distance between a structure and the shoreline) and instituting other land-use arrangements, including rolling easements (PDF), to enable wetlands and beaches to migrate inland
• Upgrading and redesigning infrastructure such as bridges, roads, culverts and stormwater systems
• Evaluating drinking water supplies with respect to climate change
• Mapping coastal hazards and developing emergency response plans with regard to sea level rise

The following case studies, examples, and related links illustrate what is being done in coastal communities to protect people and property. To find more information about activities in specific areas, visit the regional adaptation pages - links are provided after the case studies. Please note that examples on this website are not intended to be comprehensive.

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EPA’s Climate Ready Estuaries program protects key resources

EPA works with the National Estuary Programs and coastal managers under the Climate Ready Estuaries (CRE) program to prepare for the impacts of climate change. Estuaries, the transition zones where rivers meet the ocean, are particularly sensitive to climate change. CRE partners have successfully completed (PDF) vulnerability assessments, engaged stakeholders, identified climate change indicators, and initiated adaptation planning efforts. Specific CRE projects are described on the CRE website, with several of them highlighted here:

• In May 2010, the Partnership for the Delaware Estuary published an assessment (PDF) of vulnerabilities and adaptation options for tidal wetlands, drinking water supplies, and bivalve shellfish in the region. For all of these resources, the protection and/or restoration of buffers and the management of water flows were considered important for successful adaptation.
• The Charlotte Harbor National Estuary Program (CHNEP) developed a vulnerability assessment for its seven-county southwest Florida study area, and based on this information, has developed an adaptation plan with the City of Punta Gorda.
• The Sarasota Bay Estuary Program has developed a mapping visualization tool to help educate stakeholders and the public about sea level rise risks.
• In March 2010, the Piscataqua Region Estuaries Partnership in New Hampshire completed a study (PDF) assessing the capacity of existing road culverts (structures commonly placed under roads to allow water to flow) during climate-induced flood events in the Oyster River watershed. Dam and culvert capacity was evaluated under several climate change and population growth scenarios to help decision-makers set priorities for design changes in new and rebuilt facilities.
• In March 2012, vulnerability assessments for salt marshes and mudflats of the San Francisco Estuary Partnership and the Massachusetts Bays Program were published, based on the results of a novel methodology using expert elicitation. The judgments of local experts on the sensitivities of ecosystem processes to future climate conditions were used to identify "top pathways" for management adaptations.

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State Coastal Programs Prepare for Sea Level Rise

"Living shorelines" use vegetation and low rocks to protect the shoreline. Source: NOAA Ocean & Coastal Resource Management (2007)

Some states with Coastal Zone Management Programs are taking steps (PDF) to protect their coastal resources, minimize erosion, and lower risks of damage from strong storms and sea level rise. Although several of these states may not be considering future climate changes or sea level rise explicitly, many of their actions are likely to bolster resilience to expected impacts. Three sets of examples are listed below.

• California's Coastal Program requires builders applying for new shorefront development permits to consider hazards associated with increases in sea level in their project plans. See the Southwest Impacts & Adaptation page for more information about how California is preparing for sea level rise and erosion on the coast.
• In 2009, North Carolina began calculating required setbacks (the distance between a structure and the shoreline) based on the size of the structure and local erosion rate. Moving structures further from the current shoreline will likely reduce damage from strong storms, as well as potential damage from sea level rise. For more information about strategies for reducing risk of damage from storms and sea level rise in North Carolina and other Southeastern states, visit the Southeast Impacts & Adaptation page.
• Maryland and Virginia's (PDF) Coastal Programs have developed a "Living Shorelines" initiative. The initiative promotes alternatives to armoring shorelines with hard structures such as bulkheads and stone revetments, which eliminate wetlands and beaches. Alternatives include establishing oyster reefs, planting vegetation, such as marsh and dune grass, or using a combination of vegetation and strategically placed low-profile barriers such as rocks or wood.

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StormSmart Coasts Promotes Information and Resources Sharing

StormSmart Coasts Alliance was formed by the National Oceanic and Atmospheric Administration, the Gulf of Mexico Alliance, the Northeast Regional Ocean Council, and EPA. The network provides an online forum for coastal communities to find and share information about protecting coastal communities from extreme weather, sea level rise, and other climate-related hazards. Through the website, participating states have access to instructions on how to map hazards, create an emergency response plan, and recover from floods. Communities involved in the network can post webinars, studies, and funding opportunities related to coastal impacts for use by other communities in the region.

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References

1. NRC (2010). Adapting to the Impacts of Climate Change . National Research Council. The National Academies Press, Washington, DC, USA.

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