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Service Description: This project and resulting GIS data layer provides an indirect estimate of emergent, scrub-shrub and forested tidal wetland losses for 55 non-lagoonal estuaries spanning the United States West Coast. Losses are defined as those areas that were tidal wetlands prior to European settlement, but are no longer tidal wetlands today. Losses were estimated by comparing the National Wetland Inventory's mapping of current tidal wetlands to the Pacific Marine and Estuarine Fish Habitat Partnership (PMEP)’s West Coast Estuary Extent mapping. The estuary extent layer represents the likely historical extent of tidal wetlands, so areas not identified as current tidal wetlands in the National Wetlands Inventory (NWI) are considered "lost" in this analysis. This West Coast-wide mapping of tidal wetland losses will help PMEP and other organizations understand the magnitude of tidal wetland losses coastwide, and how those losses vary among estuaries, regions, and ranges of fish species of concern. The results also provide a necessary base layer for future assessments such as analysis of climate change impacts.
Map Name: PMEP Tidal Wetlands Loss
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Description: This project and resulting GIS data layer provides an indirect estimate of emergent, scrub-shrub and forested tidal wetland losses for 55 non-lagoonal estuaries spanning the United States West Coast. Losses are defined as those areas that were tidal wetlands prior to European settlement, but are no longer tidal wetlands today. Losses were estimated by comparing the National Wetland Inventory's mapping of current tidal wetlands to the Pacific Marine and Estuarine Fish Habitat Partnership (PMEP)’s West Coast Estuary Extent mapping. The estuary extent layer represents the likely historical extent of tidal wetlands, so areas not identified as current tidal wetlands in the National Wetlands Inventory (NWI) are considered "lost" in this analysis. Important limitations to be aware of when interpreting the results of this assessment:
Because PMEP’s estuary extent layer is an elevation-based map, areas lost due to fill that elevates the land surface above current tide range are not captured in the estuary extent layer or in this loss analysis.
Areas of restored, vegetated tidal wetland habitat have not been identified and incorporated into the estimation of losses, unless they were mapped through an update to the NWI post-restoration. Lagoonal estuaries were excluded from this assessment, because PMEP’s estuary extent mapping may not adequately reflect the historical extent of these features.
In many areas along the U.S. West Coast, the NWI data are quite old (>20 years) and do not accurately reflect current tidal conditions. The most likely result of this limitation is an underestimate of tidal wetland losses. Initial stages of the analysis showed that the methods worked best in larger estuaries where NWI mapping was more likely to exist at an appropriate scale, and where substantial human alteration is evident. For this reason, we focused the analysis on estuaries with >100 hectares of historical tidal wetland area, and with substantial human alterations (55 estuaries). This subset of PMEP estuaries captures the vast majority (98%) of historical west coast tidal wetlands by area.
Despite these limitations, this analysis provides a broad assessment of the magnitude and spatial distribution of tidal wetland losses across West Coast non-lagoonal estuaries, and provides decision support for conservation and restoration of West Coast estuarine resources.
This West Coast-wide mapping of tidal wetland losses will help PMEP and other organizations understand the magnitude of tidal wetland losses coastwide, and how those losses vary among estuaries, regions, and ranges of fish species of concern. The results also provide a necessary base layer for future assessments such as analysis of climate change impacts.
Service Item Id: 38146898651e4fe5a18c36e8330560e5
Copyright Text: Pacific Marine and Estuarine Fish Habitat Partnership, PSMFC GIS
Spatial Reference:
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Title: PMEP Tidal Wetlands Loss Analysis
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Comments: This project and resulting GIS data layer provides an indirect estimate of emergent, scrub-shrub and forested tidal wetland losses for 55 non-lagoonal estuaries spanning the United States West Coast. Losses are defined as those areas that were tidal wetlands prior to European settlement, but are no longer tidal wetlands today. Losses were estimated by comparing the National Wetland Inventory's mapping of current tidal wetlands to the Pacific Marine and Estuarine Fish Habitat Partnership (PMEP)’s West Coast Estuary Extent mapping. The estuary extent layer represents the likely historical extent of tidal wetlands, so areas not identified as current tidal wetlands in the National Wetlands Inventory (NWI) are considered "lost" in this analysis. Important limitations to be aware of when interpreting the results of this assessment:
Because PMEP’s estuary extent layer is an elevation-based map, areas lost due to fill that elevates the land surface above current tide range are not captured in the estuary extent layer or in this loss analysis.
Areas of restored, vegetated tidal wetland habitat have not been identified and incorporated into the estimation of losses, unless they were mapped through an update to the NWI post-restoration. Lagoonal estuaries were excluded from this assessment, because PMEP’s estuary extent mapping may not adequately reflect the historical extent of these features.
In many areas along the U.S. West Coast, the NWI data are quite old (>20 years) and do not accurately reflect current tidal conditions. The most likely result of this limitation is an underestimate of tidal wetland losses. Initial stages of the analysis showed that the methods worked best in larger estuaries where NWI mapping was more likely to exist at an appropriate scale, and where substantial human alteration is evident. For this reason, we focused the analysis on estuaries with >100 hectares of historical tidal wetland area, and with substantial human alterations (55 estuaries). This subset of PMEP estuaries captures the vast majority (98%) of historical west coast tidal wetlands by area.
Despite these limitations, this analysis provides a broad assessment of the magnitude and spatial distribution of tidal wetland losses across West Coast non-lagoonal estuaries, and provides decision support for conservation and restoration of West Coast estuarine resources.
This West Coast-wide mapping of tidal wetland losses will help PMEP and other organizations understand the magnitude of tidal wetland losses coastwide, and how those losses vary among estuaries, regions, and ranges of fish species of concern. The results also provide a necessary base layer for future assessments such as analysis of climate change impacts.
Subject: An indirect estimate of of emergent, scrub-shrub and forested tidal wetland losses for 55 non-lagoonal estuaries spanning the United States West Coast.
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Keywords: estuary,PMEP,tidal,wetlands,West,Coast,estuaries
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