Wetland Assessment Criteria 13 



emergent, palustrine forested and palustrine scrub-shrub. The coastal 

 vegetated wetland types experiencing losses during the 1954-1974 period 

 (i.e., estuarine intertidal emergent, marine intertidal and estuarine 

 intertidal forested and scrub-shrub wetlands) were not compared with 

 palustrine wetlands. This is because these wetlands only represent about 

 5 percent of total U.S. estuarine and palustrine wetlands. The Index of 

 Loss numbers generated were not meaningful when compared with 

 palustrine wetlands having a significantly higher base acreage. 



The coastal region, or that area along or near the coastline having marine 

 intertidal and estuarine system wetland types, has experienced a signi- 

 ficant loss of vegetated wetlands and associated values in the lower 48 

 States. During the NWI trends study, estuarine wetlands losses were 

 greatest in California, Florida, Louisiana, New Jersey and Texas. 

 Louisiana's coastal marsh losses were mostly due to submergence of 

 coastal wetlands. Dredge and fill development was a significant cause of 

 coastal wetlands losses in California, Florida, New Jersey and Texas. In 

 other coastal areas, urban development was the major cause of wetland 

 loss. In general, declining wetland types in the coastal region warrant 

 priority consideration for protection and Federal and State acquisition. 



The Index of Loss results for palustrine emergent, palustrine forested and 

 palustrine scrub-shrub wetland types are listed in Table 2, ranked from 

 highest to lowest losses per ecoregion division. A high Index of Loss 

 indicates a large magnitude of loss, a large percent of wetland base loss or 

 both (as well as their functions and values) during the 1954-74 study 

 period. 



The Index of Loss data show that certain ecoregions of the U.S. had 

 substantially higher losses of palustrine wetlands than other ecoregions. 

 These data can be used, if desired, to set national acquisition priorities 

 among various ecoregions. However, it should be recognized that the 

 trends study period data do not reflect wetland trends prior to 1954 or after 

 1974. Also, the trends study data are not refined enough to show sub- 

 regional differences within the ecoregion (e.g., high wetland losses 

 occurred within an ecoregion section, although losses were low within the 

 same ecoregion division). For these reasons, decisionmakers should be 

 cautious with their use of the Index of Loss information. States having 

 specific information or data for these periods, or more specific infor- 

 mation or data during the trends study period, may use such documentable 

 information to support statements made in a wetland acquisition docu- 

 ment indicating estimated levels (e.g., high, moderate, low) of wetland 

 loss by a State or subregion. Such estimates or indices of wetland loss, 

 however, are not directly comparable with the Index of Loss estimates 

 based on trends study data (refer to Table 2). 



National Wetlands Priority Conservation Plan 



