Coastal Impacts, Adaptation, and Vulnerabilities - Climate ...

xxviCoastal Impacts, Adaptation, and Vulnerabilitiesffffffffthe sign of projected changes to the coast of storm-related hazards that dependon a combination of factors such as frequency, track, intensity, and storm size,any sea-level rise is virtually certain to exacerbate storm-related hazards. HighConfidence.Although sea-level rise and climate change have occurred in the past, theincreasing human presence in the coastal zone will make the impacts differentfor the future. Land use and other human activities often inhibit the naturalresponse of physical processes and adaptation by plants and animals. In someareas, erosion and wetland loss are common because sediment budgets havebeen reduced, while, in other regions, excess sediment is in-filling harbors, channels,and bays. High Confidence.Observations continue to indicate an ongoing, warming-induced intensificationof the hydrologic cycle that will likely result in heavier precipitation events and,combined with sea-level rise and storm surge, an increased flooding severity insome coastal areas, particularly the northeast U.S. Moderate Confidence.Temperature is primarily driving environmental change in the Alaskan coastalzone. Sea ice and permafrost make northern regions particularly susceptible totemperature change. For example, an increase of two degrees Celsius could basicallytransform much of Alaska from frozen to unfrozen, with extensive implications.Portions of the north and west coast of Alaska are seeing dramatic increasesin the rate of coastal erosion and flooding due to sea ice loss and permafrostmelting. As a consequence, several coastal communities are planning to relocateto safer locations. Relocation is a difficult decision that is likely to become morecommon in the future for many coastal regions. High Confidence.Methane is a primary greenhouse gas. Large reserves of methane are bound-upin Alaska’s frozen permafrost. These are susceptible to disturbance and methanerelease if the Arctic continues to warm. The additional methane released mayresult in even greater greenhouse warming of the atmosphere. High Confidence.Vulnerability and Impacts on Natural ResourcesClimate and non-climate stressors originating from terrestrial and marine sources interactat the coast to influence coastal habitats (Nicholls et al., 2007; Rosenzweig et al.,2007). Increased temperatures and altered precipitation patterns interact with changingland 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 shorelineto exacerbate coastal erosion, flooding, and saltwater intrusion. As the physical environmentchanges, the range of a particular ecosystem will expand, contract, or migrate inresponse. Changes in range as well as structure and function are evident in many typesof ecosystems.The interactions of the many stressors result in complex changes to natural coastalsystems that may not be predicted by the response from any single stressor. Positiveand negative impacts occur when the impact of one stressor is either strengthened or