Description: Reason for Selection Larger, better connected wetlands are positively associated with fish (Meynecke et al. 2008), shrimp (Turner 1977), and marsh birds. In particular, seaside sparrow (Benoit and Askins 2002, Rush et al. 2009), saltmarsh sharp-tailed sparrow (Benoit and Askins 2002), and marsh wren (Rush et al. 2009) have been associated with marsh area effects. Other species are expected to be limited based on home range size. In addition, wave attenuation is increased with wetland area (Shepard et al. 2011). Over time, a decrease in patch size will correspond to marsh degradation and wetland loss. Input Data National Wetlands Inventory (NWI) data (accessed 15 May 2014) and 2011 National Land Cover Dataset (NLCD) data served as inputs for this indicator. We pulled the “Estuarine and Marine Wetland” class from NWI and the “Emergent Wetland” class from NLCD. For the Atlantic Coast, we used an NWI update by The Nature Conservancy's South Atlantic Marine Bight Assessment. Salt marsh, salt marsh impoundments, and tidal flats corresponded to this layer. Mapping Steps 1) The NLCD emergent wetland class was masked with NWI's "Estuarine and Marine Wetland" category to distinguish estuarine marshes from freshwater marshes. 2) The Spatial Analyst-Region Group function was used to delineate individual patches using an 8-neighbor rule. The method defines patches by clumping all wetland cells directly adjacent, or diagonal to each other, into individual patches. 3) The wetland patches were reclassified into 5 quantiles of wetland sizes (in hectares): 0 = 1-328 ha (low) 1 = 329-1,228 ha 2 = 1,229-3,087 ha 3 = 3,088-6,088 ha 4 = 6,088-15,154 ha (high) Defining the Spatial Extent of Ecosystems Estuarine marshes and estuarine open water were defined by the National Wetlands Inventory (NWI) (U.S. Fish and Wildlife Service 2014) for the Florida Gulf Coast. NWI broadly classified the estuarine zone as "Estuarine and Marine Wetland" (estuarine marsh) and "Estuarine and Marine Deepwater" (estuarine open water). Similarly, for the Atlantic Coast, we used an NWI update by The Nature Conservancy's South Atlantic Marine Bight Assessment. Their classifications of salt marsh, salt marsh impoundments, and tidal flat classifications corresponded to the estuarine marsh ecosystem. During the process of rescaling data to a 200 m resolution, ecosystems were overlaid and overlaps were handled by ordering them from high (never excluded by another ecosystem) to low (always excluded by another ecosystem). To avoid data loss, linear features, such as maritime forests, were ranked relatively high. The ranking proceeded as: 9) maritime forest, 8) beaches and dunes, 7) estuaries, 6) major waterbodies, 5) localized data on pine land cover, 4) forested wetlands, 3) freshwater marsh, 2) longleaf pine range, 1) upland hardwoods. GIS Processing All indicators were initially computed, or in the case of existing data, were resampled to 1 ha spatial resolution using the nearest neighbor method. For computational reasons, we then used the Spatial Analyst-Aggregate function to rescale the resolution to 200 m. The aggregate function avoided loss of detail by taking the maximum value of each cell in the conversion (e.g., species presence). Past, Present, and Future Since the index is dependent on the NLCD, future monitoring will be relatively easy. A decrease in patch size will be an early sign of marsh degradation.Questions/Comments As a wide variety of marsh patch sizes correspond to species and ecosystem services (noted above), the quantile index is a simple, objective way of quantifying the functional value of different patch sizes. Known Issues In the future, a measure of intertidal wetlands may be useful to include, but data on marsh vegetation composition is currently lacking. The NWI is currently being used to distinguish “estuarine marsh” from freshwater marshes, but its accuracy in this regard is unknown. Literature Cited Benoit, L.K., Askins, R.A., 2002. Relationship between habitat area and the distribution of tidal marsh birds. The Wilson Bulletin 114, 314-323. Meynecke, J.O., Lee, S.Y., Duke, N., 2008. Linking spatial metrics and fish catch reveals the importance of coastal wetland connectivity to inshore fisheries in Queensland, Australia. Biological Conservation 141, 981-996. Rush, S.A., Soehren, E.C., Woodrey, M.S., Graydon, C.L., Cooper, R.J., 2009. Occupancy of select marsh birds within northern Gulf of Mexico tidal marsh: current estimates and projected change. Wetlands 29, 798-808. Shepard, C.C., Crain, C.M., Beck, M.W., 2011. The protective role of coastal marshes: a systematic review and meta-analysis. PLoS One 6. Turner, R.E., 1977. Intertidal vegetation and commercial yields of penaeid shrimp. Transactions of the American Fisheries Society 106, 411-416. U.S. Fish and Wildlife Service 2014. National Wetlands Inventory - Wetlands. < http://www.fws.gov/wetlands/>.