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

126 Coastal Impacts, Adaptation, and Vulnerabilitiesanother 2.7 million acres between 1950 and 1980. With development, the Bay has losthalf of the forested shorelines, over half of the wetlands, about 80 percent of underwatergrasses, and more than 98 percent of the oysters. The result has been a general decline inthe health of the Bay.Several states in the watershed have made a voluntary pledge to “Save the Bay” bycreating a blueprint for restoring the Bay’s health. On May 12, 2009, President Obamasigned the Chesapeake Bay Protection and Restoration Executive Order (Executive Order13508) to “protect and restore the health, heritage, natural resources, and social andeconomic value of the Nation’s largest estuarine ecosystem and the natural sustainabilityof its watershed.” The restoration of the water quality and aquatic ecosystems inthe Bay has proven to be difficult and will only become more complex with the addedimpacts of climate change.The selection of the Bay as a case study in this chapter of the NCA was based on severalfactors. Managing the Bay requires coordination among several states, making it atruly regional effort spanning a large geographic area. The Bay is a nationally importantresource that is in critical condition; a significant regulatory commitment has been madeto this area and substantial monitoring efforts are underway to support its restoration.Although future climate conditions are likely to be warmer, the magnitude and rateof warming over the 21st century is uncertain. The location of the Bay is also interestingfrom a precipitation standpoint, with considerable uncertainty surrounding futureconditions; in other words, the area could be wetter or drier. Given the enormity of theBay and the issues it faces, this case study focuses more narrowly on the climate changeimpacts and adaptation measures relevant to managing water quality and aquatic ecosystemsin Maryland, Pennsylvania, and Virginia.The following sections provide an overview of the climate impacts anticipated to occurin the Bay (Section 2), a snapshot of a set of plausible climate futures (Section 3), and,finally, an overview of state-level adaptation planning across the Bay (Section 4).2: Climate Change Impacts on Water Quality and EquaticEcosystems for the Chesapeake Bay2.1 Changes in Physical ClimateA high level overview of the projected changes in the Bay’s physical climate is shownin Table A-1. These changes, along with related changes in streamflow, are discussed inmore detail below.Temperature changes are relative to the 1971-2000 average, with results shown forboth the lower B2 and higher A2 emission scenarios, averaged from seven climate models(Najjar et al., 2009). Ranges represent the multi-model mean ±1 standard deviation.For the earlier periods of 2010 to 2039 and 2040 to 2069, only the A2 are shown, becausethe differences between the multi-model averages for the two scenarios are lessthan 0.2°C. These scenarios were examined by Najjar et al. (2009) because they bracketthe range of emissions from the IPCC Third Assessment Report (Nakićenović & Swart,2000). Sea-level changes are relative to 1990. End-of-century projections are from Najjaret al. (2010), which is based on the statistical model presented in Rahmstorf (2007). The