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We compiled spatial data on land cover from the National Land Cover Database, CALVEG, and other sources to develop a comprehensive “wall-to-wall” map of land cover for three categories: natural, agriculture, and developed. Natural lands are completely composed of native habitats. Agriculture is further divided into agriculture, prime agriculture, and agricultural wetlands. Prime agriculture, as defined by the USDA, recognizes highly productive agricultural lands that require minimum inputs, and that are generally surrounded by undeveloped, non-agricultural open space. Agricultural wetlands are areas actively being used for agriculture from row crops to grazing, that are also delineated as wetlands by the National Wetland Inventory (NWI). For the purposes of this assessment, developed areas include fourteen types of built environment ranging from developed open space to high intensity development, including transportation and other infrastructure. This layer was then overlaid with our Conservation Management Status layer to identify the conservation management status of these habitats.
We calculated habitat specific vulnerability for each analytic unit. We also calculated a Vulnerability Index as an area weighted Vulnerability of all habitats within an analytic unit. To do this we summed the vulnerability of all habitats within a given analytic unit, each weighted by the area of habitat within the analytic unit. As a ratio, habitat specific Vulnerability or the Vulnerability Index is independent of area, and describes each habitat’s or the landscape’s ability to maintain the current habitat area in the face of sea level rise within each analytical unit. Potential Impact is calculated as the area of sea level rise exposure weighted by that habitat’s Sensitivity,or degree of impact from, that exposure type. Adaptive Capacity is calculated as the area within our analytic zone of natural habitat available to any given habitat to transgress inland in response to sea level rise, excluding that habitat category, the built environment, and habitats lower in elevation. Vulnerability (V) represents the ratio of Potential Impact relative to Adaptive Capacity and ranges from 0 to 2. With no Potential Impact, V= 0. As Potential Impact increases relative to Adaptive Capacity so does V, up to V = 2, where there is no Adaptive Capacity. V = 1.2 a threshold ratio for Adaptive Capacity relative to Potential Impact. V = 0.8 to 1.2 represents the range for which Adaptive Capacity roughly equals Potential Impact. Above V = 1.2 there is more calculated Potential Impact than Adaptive Capacity, for ease in description, we refer to this range as "high vulnerability". Below V = 1.2 Potential Impact is less than or equal to Adaptive Capacity, for ease in description, we refer to this range as “lower vulnerability", or "resilient". We integrated the Coastal Management Status with the analytic units to stratify between Conserved and Non-Conserved.