[Source: USGS, full PDF document: (LINK). Extract, edited.]
Coastal Impacts, Adaptation, and Vulnerabilities - A Technical Input to the 2013 National Climate Assessment
About the National Climate Assessment:
The National Climate Assessment (NCA) is being conducted under the auspices of the Global Change Research Act of 1990. The GCRA requires a report to the President and the Congress every four years that integrates, evaluates, and interprets the findings of the U.S. Global Change Research Program (USGCRP); analyzes the effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems, and biological diversity; and analyzes current trends in global change, both human-induced and natural, and projects major trends for the subsequent 25 to 100 years.
This Technical Input was produced by a team of experts at the request of the NCA Development and Advisory Committee. It will be available for use as reference material by all NCA author teams.
The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect the views of NOAA or the Department of Commerce.
Date Submitted to the NCA Development and Advisory Committee: March 1, 2012; revised version November 16, 2012
Editorial Support provided by: The Stiefel Group
Front Cover Figure: The map illustrates U.S. coastal and Great Lakes counties. Source: U.S. Environmental Protection Agency
Suggested Citation: Burkett, V.R. and Davidson, M.A. [Eds.]. (2012). . Cooperative Report to the 2013 National Climate Assessment., pp. 150.
- Virginia Burkett – Co-Chair, U.S. Geological Survey
- Margaret Davidson – Co-Chair, National Oceanic and Atmospheric Administration
- Ralph Cantral, National Climate Assessment
- John Haines, U.S. Geological Survey
- John Hall, U.S. Department of Defense
- Fred Lipschultz, National Climate Assessment
- Anne Waple, National Oceanic and Atmospheric Administration
- Jordan West, U.S. Environmental Protection Agency
We would like to thank the U.S. Geological Survey (USGS), the National Oceanic and Atmospheric Administration (NOAA), and the National Aeronautics and Space Administration (NASA) for providing financial resources to support the development of this technical input including personnel, travel, and accommodations for workshop participants.
We thank the U.S. Global Change Research Program (USGCRP) for providing a shared online workspace as well as technical support during phone and web-based meetings. We are grateful to Susanne Moser (Susanne Moser Research & Consulting) and Richard Moss (University of Maryland) for giving presentations during the workshop. We appreciate the constructive comments received from three formal reviewers on the entire technical input and several external reviewers on individual chapters during the preparation. We are deeply grateful to The Stiefel Group (Murielle Gamache-Morris and Emily Wallace) for their skillful edits and the organizational support they provided to the writing team.
- Adaptation1: Adjustment in natural or human systems to moderate harm or exploit beneficial opportunity in response to actual or expected climatic stimuli or their effects. Various types of adaptation can be distinguished, including anticipatory, autonomous, and planned adaptation:
- Anticipatory adaptation – Adaptation that takes place before impacts of climate change are observed. Also referred to as proactive adaptation.
- Autonomous adaptation – Adaptation that does not constitute a conscious response to climatic stimuli but instead is triggered by ecological changes in natural systems and by market or welfare changes in human systems. Also referred to as spontaneous adaptation.
- Planned adaptation – Adaptation as the result of a deliberate policy decision based on an awareness that conditions have changed or are about to change and that action is required to return to, maintain, or achieve a desired state.
- Climate1: Climate in a narrow sense is usually defined as the average weather or, more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. The classical period of time is 30 years as defined by the World Meteorological Organization (WMO).
- Climate Change1: Climate change refers to any change in climate over time due to natural variability or human activity.
- Disaster2: Severe alterations in the normal functioning of a community or a society resulting from the interaction of hazardous physical events and vulnerable social conditions that leads to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery.
- Disaster Risk2: The likelihood over a specified time period of severe alterations in the normal functioning of a community or a society resulting from the interaction of hazardous physical events and vulnerable social conditions that leads to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery.
- Exposure3: The nature and degree to which a system is exposed to significant climatic variations.
- Mainstreaming: The incorporation of climate change considerations into established or ongoing development programs, policies, or management strategies rather than developing adaptation and mitigation initiatives separately.
- Mitigation1: An anthropogenic intervention to reduce the anthropogenic forcing of the climate system, including strategies to reduce greenhouse gas sources and emissions and enhance greenhouse gas sinks.
- Resilience2: The ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event in a timely and efficient manner through ensuring the preservation, restoration, or improvement of its essential basic structures and functions.
- Risk3: Combination of the probability of an event and its consequences.
- Sensitivity1: Sensitivity is the degree to which a system is affected either adversely or beneficially by climate variability or change. The effect may be direct, such as a change in crop yield in response to a change in the mean, range, or variability of temperature, or indirect, such as damages caused by an increase in the frequency of coastal flooding due to sea-level rise.
- Thermal Expansion4: In connection with sea level, this refers to the increase in volume (and decrease in density) that results from warming water. A warming of the ocean leads to an expansion of the ocean volume and hence an increase in sea level.
- Threshold1: The level of magnitude of a system process at which sudden or rapid change occurs. A point or level at which new properties emerge in an ecological, economic or other system, invalidating predictions based on mathematical relationships that apply at lower levels.
- Transformation2: The altering of fundamental attributes of a system (including value systems; regulatory, legislative, or bureaucratic regimes; financial institutions; and technological or biological systems).
- Vulnerability1: the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity.
(1) IPCC, 2007: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden & C.E. Hanson, (Eds.), Cambridge University Press, Cambridge, UK, glossary, pp. 869-883.
(2) IPCC, 2007: Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, & L.A. Meyer (Eds.) Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Section 2.3.1.
(3) IPCC, 2001: Climate Change 2001: Impacts, Adaptation, and Vulnerability. J. J. McCarthy, O. F. Canziani, N. A. Leary, D. J. Dokken and K. S. White (eds) Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, glossary, pp. 982-996.
(4) IPCC, 2001: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change [Houghton, J.T.,Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K.Maskell, and C.A. Johnson (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, glossary, pp. 787-797.
The coast has long provided communities with a multitude of benefits including an abundance of natural resources that sustain economies, societies, and ecosystems. Coasts provide natural harbors for commerce, trade, and transportation; beaches and shorelines that attract residents and tourists; and wetlands and estuaries that are critical for fisheries and water resources. Coastal ecosystems provide critical functions to cycle and move nutrients, store carbon, detoxify wastes, and purify air and water. These areas also mitigate floods and buffer against coastal storms that bring high winds and salt water inland and erode the shore. Coastal regions are critical in the development, transportation, and processing of oil and natural gas resources and, more recently, are being explored as a source of energy captured from wind and waves. The many benefits and opportunities provided in coastal areas have strengthened our economic reliance on coastal resources. Consequently, the high demands placed on the coastal environment will increase commensurately with human activity. Because 35 U.S. states, commonwealths, and territories have coastlines that border the oceans or Great Lakes, impacts to coastline systems will reverberate through social, economic, and natural systems across the U.S.
Impacts on coastal systems are among the most costly and most certain consequences of a warming climate (Nicholls et al., 2007). The warming atmosphere is expected to accelerate sea-level rise as a result of the decline of glaciers and ice sheets and the thermal expansion of sea water. As mean sea level rises, coastal shorelines will retreat and low-lying areas will tend to be inundated more frequently, if not permanently, by the advancing sea. As atmospheric temperature increases and rainfall patterns change, soil moisture and runoff to the coast are likely to be altered. An increase in the intensity of climatic extremes such as storms and heat spells, coupled with other impacts of climate change and the effects of human development, could affect the sustainability of many existing coastal communities and natural resources.
This report, one of a series of technical inputs for the third NCA conducted under the auspices of the U.S. Global Change Research Program, examines the known effects and relationships of climate change variables on the coasts of the U.S.. It describes the impacts on natural and human systems, including several major sectors of the U.S. economy, and the progress and challenges to planning and implementing adaptation options. Below we present the key findings from each chapter of the report, beginning with the following key findings from Chapter 1:
- Changes in the environment associated with human development activities compromise the ability of the coasts to continue to provide a multitude of benefits including food, clean water, jobs, recreation, and protection from storms. In some cases, these benefits are further impacted by the changing climate. High Confidence.
- Adapting to the changing climate will be a challenge for coastal economies that contributed $8.3 trillion to the GDP in 2010 and depend on coastal landforms, water resources, estuaries, and other natural resources to sustain them. High Confidence.
- Coastal states and communities will need strategies to enable them to manage current stressors and the confounding impacts of a changing climate to conserve, protect, and restore coastal habitats. Easing the existing pressures on coastal environments to improve their resiliency is one method of coping with the adverse effects of climate change. High Confidence.
Physical Climate Forces
A changing global climate combined with intense human activity imposes additional stresses on coastal environments. Although the climate is warming at a global scale, the impacts and the timing of the impacts are highly variable across coastal regions. Some effects, such as rising sea level, are already evident in increased erosion of beaches, more frequent flooding from both rivers and tidal surge, and wetlands converting to open water. Sea surface temperatures have risen over much of the globe, and hurricane activity has increased over the past several decades, particularly in the Atlantic basin, although it is uncertain whether these storm changes exceed the levels expected from natural causes. In addition, increased uptake of atmospheric carbon dioxide by the oceans has increased ocean acidity that threatens coral reefs and shellfish. The primary driving forces are: sea-level rise, changes in temperature, precipitation, major storm events including waves, winds and currents, and changing ocean circulation patterns. These driving forces interact in complex ways with the landforms and infrastructure that make the coasts particularly vulnerable to many of the impacts of climate change.
- The coasts of the U.S. are home to many large urban centers and important infrastructure such seaports, airports, transportation routes, oil import and refining facilities, power plants, and military bases. All are vulnerable to varying degrees to impacts of global warming such as sea-level rise, storms, and flooding. High Confidence.
- Physical observations collected over the past several decades from the land, coasts, oceans, and the atmosphere, as well as environmental indicators, show that warming and some related environmental changes are occurring globally at rates greater than can be expected due to natural processes. These climate-related changes are highly varied, but some are likely due in large part to anthropogenically increased atmospheric concentrations of greenhouse gases and altered land surface properties. High Confidence.
- Findings from many independent scientific studies conclude that these changes are consistent with global warming. The primary changes observed are rising sea level and average global air, land, and ocean temperatures; heightening temperature and precipitation extremes in some regions; and increasing levels of oceans acidification and rates of glacier and ice sheet melt. High Confidence.
- Most coastal landforms, such as barrier islands, deltas, bays, estuaries, wetlands, coral reefs, are highly dynamic and sensitive to even small changes in physical forces and feedbacks such as warming, storms, ocean circulation, waves and currents, flooding, sediment budgets, and sea-level rise. High Confidence.
- The effects of sea-level rise on coasts vary considerably from region-to-region and over a range of spatial and temporal scales. Land subsidence in certain locations causes relative sea-level rise to exceed global mean sea-level rise. Land uplift such as that found in Alaska and the Northwestern Pacific coast can reduce effects of global mean rise. The effects will be greatest and most immediate on low-relief, low-elevation parts of the U.S. coast along the Gulf of Mexico, mid-Atlantic states, northern Alaska, Hawaii, and island territories and especially on coasts containing deltas, coastal plains, tidal wetlands, bays, estuaries, and coral reefs. Beaches and wetlands on steep cliff coasts and shores backed with seawalls may be unable to move landward or maintain their landform with sea-level rise. Many areas of the coast are especially vulnerable because of the often detrimental effects of development on natural processes. High Confidence.
- The gradual inundation from recent sea-level rise is evident in many regions such as the mid-Atlantic and Louisiana where high tides regularly flood roads and areas that were previously dry, and in stands of “ghost forests,” in which trees are killed by intrusion of brackish water. High Confidence
- Sea level change and storms are dominant driving forces of coastal change as observed in the geologic record of coastal landforms. Increasingly, sea-level rise will become a hazard for coastal regions because of continued global mean sea-level rise, including possibly accelerated rates of rise that increase risk to coastal regions. As the global climate continues to warm and ice sheets melt, coasts will become more dynamic and coastal cities and low-lying areas will be increasingly exposed to erosion, inundation, and flooding. High Confidence.
- No coordinated, interagency process exists in the U.S. for identifying agreed upon global mean sea-level rise projections for the purpose of coastal planning, policy, or management, even though this is a critical first step in assessing coastal impacts and vulnerabilities. High Confidence.
- Global sea level rose at a rate of 1.7 millimeters/year during the 20th century. The rate has increased to over 3 millimeters/year in the past 20 years and scientific studies suggest high confidence (>9 in 10 chance) that global mean sea level will rise 0.2 to 2 meters by the end of this century. Some regions such as Louisiana and the Chesapeake Bay will experience greater relative rise due to factors such as land subsidence, gravitational redistribution of ice-sheet meltwater, ocean circulation changes, and regional ocean thermostatic effects. Other regions undergoing land uplift, such as Alaska, will experience lesser sea-level rise. High Confidence.
- Variability in the location and time-of-year of storm genesis can influence landfalling storm characteristics, and even small changes can lead to large changes in landfalling location and impact. Although scientists have only low confidence in the sign of projected changes to the coast of storm-related hazards that depend on a combination of factors such as frequency, track, intensity, and storm size, any sea-level rise is virtually certain to exacerbate storm-related hazards. High Confidence.
- Although sea-level rise and climate change have occurred in the past, the increasing human presence in the coastal zone will make the impacts different for the future. Land use and other human activities often inhibit the natural response of physical processes and adaptation by plants and animals. In some areas, erosion and wetland loss are common because sediment budgets have been reduced, while, in other regions, excess sediment is in-filling harbors, channels, and bays. High Confidence.
- Observations continue to indicate an ongoing, warming-induced intensification of the hydrologic cycle that will likely result in heavier precipitation events and, combined with sea-level rise and storm surge, an increased flooding severity in some coastal areas, particularly the northeast U.S.. Moderate Confidence.
- Temperature is primarily driving environmental change in the Alaskan coastal zone. Sea ice and permafrost make northern regions particularly susceptible to temperature change. For example, an increase of two degrees Celsius could basically transform much of Alaska from frozen to unfrozen, with extensive implications. Portions of the north and west coast of Alaska are seeing dramatic increases in the rate of coastal erosion and flooding due to sea ice loss and permafrost melting. As a consequence, several coastal communities are planning to relocate to safer locations. Relocation is a difficult decision that is likely to become more common in the future for many coastal regions. High Confidence.
- Methane is a primary greenhouse gas. Large reserves of methane are bound-up in Alaska’s frozen permafrost. These are susceptible to disturbance and methane release if the Arctic continues to warm. The additional methane released may result in even greater greenhouse warming of the atmosphere. High Confidence.
Vulnerability and Impacts on Natural Resources
Climate and non-climate stressors originating from terrestrial and marine sources interact at the coast to influence coastal habitats (Nicholls et al., 2007; Rosenzweig et al., 2007). Increased temperatures and altered precipitation patterns interact with changing land use and land cover practices to affect soil moisture, ground water levels, hydrology, sediment supply, and salinity in watersheds. Sea-level rise, changing ocean currents, increased wave heights, and intensification of coastal storms interact with the shoreline to exacerbate coastal erosion, flooding, and saltwater intrusion. As the physical environment changes, the range of a particular ecosystem will expand, contract, or migrate in response. Changes in range as well as structure and function are evident in many types of ecosystems.
The interactions of the many stressors result in complex changes to natural coastal systems that may not be predicted by the response from any single stressor. Positive and negative impacts occur when the impact of one stressor is either strengthened or weakened by variation in another, and the combined influence of multiple stressors can result in unexpected ecological changes if populations or ecosystems are pushed beyond a critical threshold or tipping point (Harley et al., 2006; Lubchenco & Petes, 2010). Both theoretical and empirical examples of thresholds are rising and increasing knowledge about how climate and non-climate stressors interact to propel sudden shifts in ecosystems. These examples also show that many of the responses of natural systems are linked to those of human systems.
- Multiple stressors interact at the coast, which directly impacts natural resources. The responses of natural coastal systems to climate change are complex and subject to nonlinear changes and tipping points. Many of these responses are heavily influenced by the way they are linked with human systems. High Confidence.
- Wetland ecosystems are vulnerable to relative rise in water levels and projected increases in storm activity in zones of significant human use. High Confidence.
- Mangrove range will expand as minimum temperatures increase. High Confidence.
- Coastal forests will tend to migrate upslope and poleward where they are able to keep pace with changing habitat conditions. High Confidence.
- The structure and functioning of estuary and coastal lagoon systems will change with alterations in habitat suitability and the timing of long-standing processes. High Confidence.
- Dynamic barrier island landscapes naturally migrate in response to storm activity and sea-level rise. This process will be confounded by human alterations. High Confidence.
- Because of altered sediment supplies and local subsidence, deltas, and the biodiversity they support, are at risk to drowning during rising sea levels. High Confidence.
- Mudflats are susceptible to threshold changes caused by the combined effects of sea-level rise, temperature, land use, altered flows, and increased nutrient runoff. High Confidence.
- Complex interactions between physical and biological factors, which make responses to climate change difficult to predict, have been demonstrated in rocky shore communities. High Confidence.
- Sea ice ecosystems are already being adversely affected by the loss of summer sea ice. Further changes are expected. High Confidence.
Vulnerability and Impacts on Human Development
Societal vulnerability of U.S. coasts is comprised of the vulnerabilities of economic sectors and associated livelihoods, water resources, energy, transportation, national defense, investments in homes and other buildings, and the health and well-being of a diverse concentration of people from natives to recent immigrants and from the very poor to the tremendously wealthy. The interactions of climate-related vulnerabilities with other stressors such as economic downturn, environmental degradation, or pressures for development pose further analytical challenges. Because coastal watershed counties house a majority of U.S. cities, a significant percentage of the nation’s population may be more vulnerable to impacts under climate change and face loss of jobs, supply chain interruptions, and threats to public health, safety, and well-being as a result.
- Expanding economic and population exposure along the coast significantly increases the risk of harm and exposes already vulnerable communities to the impacts of climate change. Since 1980, roughly half of the nation’s new residential building permits were issued in coastal counties, which substantially increases vulnerability and risk of loss and adds to already populated and densely developed metropolitan areas. High Confidence.
- The full measure of human vulnerability and risk is comprised of the vulnerabilities of human development, economic sectors, associated livelihoods, and human well-being. The interactions of climate-related vulnerabilities with other stressors in the coastal zone pose analytical challenges when coupled with the lack of quantitative, multi-stressor vulnerability assessments. High Confidence.
- Storm surge flooding and sea-level rise pose significant threats to public and private infrastructure that provides energy, sewage treatment, clean water, and transportation of people and goods. These factors increase threats to public health, safety, and employment in the coastal zone. High Confidence.
- Systematic incorporation of climate risk into the insurance industry’s rate-setting practices and other business investment decisions could present a cost-effective way to deal with low probability, high severity weather events. Without reform, the financial risks associated with both private and public hazard insurance are expected to increase as a result of expected climate change and sea-level rise. High Confidence.
- Expected public health impacts include a decline in seafood quality, shifts in disease patterns and increases in rates of heat-related morbidity. Better predictions of coastal related public health risks will require sustained multi-disciplinary collaboration among researchers and health practitioners in the climate, oceanography, veterinary, and public health sciences. Moderate Confidence.
- Although the Department of Defense (DoD) has started to consider the impacts of climate change on coastal installations, operations, and military readiness, the DoD requires actionable climate information and projections at mission-relevant temporal and spatial scales to maintain effective training, deployment, and force sustainment capabilities. High Confidence.
Adaptation and Mitigation
Adaptation is emerging as an essential strategy for managing climate risk, and a broad range of adaptation initiatives are being pursued across a range of geopolitical scales. This interest in adaptation has emerged from: increased awareness that climate impacts are already occurring and unavoidable; growing availability of knowledge, data, and tools for the assessment of climate risk; and the interest of government agencies, businesses, and communities in increasing their resilience to current climate variability and future climate change.
Adaptation planning activities are increasing, and tools and resources are now more available and accessible. Frequently, plans are being developed at varied spatial scales based upon the on-the-ground needs and adaptation drivers in the particular area; therefore, they are not easily integrated or comparable across geographic, sectoral, or political boundaries. Adaptation strategies are often developed separately from other existing planning efforts rather than being effectively and efficiently integrated into existing coastal management and policy regimes. More efficiency can be achieved through integration into overall land use planning and ocean and coastal management policies and practices.
Although progress is being made in anticipatory adaptation planning, the implementation of adaptation plans has proceeded more slowly due to a variety of barriers. Some implementation is occurring via changes in regulations and policy and decisions in transportation, infrastructure, land use, and development; however, challenges remain in translating adaptation planning efforts into increased resilience. Although many adaptation actions for coastal areas can be categorized as ‘no regrets’ actions that can be implemented under a range of climate scenarios and pose few opportunity costs, more substantive actions may have larger financial, policy, or legal hurdles. Overlapping and sometimes conflicting laws, often designed without consideration of a changing climate, can prevent the adoption of adaptive measures.
- Although adaptation planning activities in the coastal zone are increasing, they generally occur in an ad hoc manner and at varied spatial scales dictated by on-the-ground needs and adaptation drivers in the particular area. Efficiency of adaptation can be improved through integration into overall land use planning and ocean and coastal management. High Confidence.
- In some cases, adaptation is being directly integrated, or mainstreamed, into existing decision-making frameworks regarding zoning and floodplain, coastal, and emergency management, but these frameworks are not always perfect fit and sometimes existing laws pose a barrier to implementation. Very High Confidence.
- Tools and resources to support adaptation planning are increasing but technical and data gaps persist. As adaptation planning has evolved, recognition has grown regarding the need for detailed information that is compatible with organizational decision-making processes and management systems. Very High Confidence.
- Although adaptation planning has an increasingly rich portfolio of case studies that contribute to shared learning, the implementation of adaptation plans has proceeded at a much slower pace. Very High Confidence.
- Elements commonly found in adaptation plans include vulnerability assessments, monitoring and indicators, capacity building, education and outreach, regulatory and programmatic changes, implementation strategies, and a sector-by-sector approach. Very High Confidence.
- Although state and federal governments play a major role in facilitating adaptation planning, most coastal adaptation will be implemented at the local level. Local governments are the primary actors charged with making the critical, basic land-use and public investment decisions and with working with community stakeholder groups to implement adaptive measures on the ground. Very High Confidence.
Climate change is altering all types of ecosystems and impacting human welfare and health, but effects are highly varied, pronounced along coasts, and likely to accelerate in decades ahead. A lack of understanding of the cumulative effects of climate and non-climate stressors as well as the interactions between human and natural systems currently limits our ability to predict the extent of climate impacts. An integrated scientific program that seeks to learn from the historic and recent geologic past, and monitors ongoing physical, environmental, and societal changes will improve the level of knowledge and reduce the uncertainty about potential responses of coasts to sea-level rise and other drivers of coastal change. This, in turn, will improve the ability of communities to assess their vulnerability and to identify and implement adaptation options that address the impacts and associated uncertainties of the projections.