8 Wetland Assessment Criteria 



during the wetter winter and spring months. Farmed wetlands may 

 quickly recover functional values without continued use of pumping and 

 dike maintenance. As such, many wetlands in agricultural land uses 

 have high potential for being restored or having their functional values 

 increased. 



The Service, under the NWI, studied trends in wetland habitats in the 

 conterminous United States (Alaska, Hawaii, Puerto Rico and U.S. Trust 

 Territories were not included in the study) during the 20-year period 

 between 1954 and 1974 (trends study) to develop information on losses and 

 gains of wetland types (Frayer et al., 1983). The NWI trends study was 

 designed to obtain a high degree of accuracy and precision at the national 

 level. During this study, less emphasis was placed on sub-national levels 

 (e.g., States); thus, information on the location of wetland losses (or 

 gains) is statistically less meaningful at State levels and for certain 

 regions. The NWI trends study did not address the significant reduction 

 in quality of many wetlands. 



The trends study did not address all types of wetlands. Marine subtidal 

 and riverine wetlands were not evaluated because of the relatively small 

 expected change in these types. Also, submerged vegetated or aquatic bed 

 wetlands, an essential habitat for commercial and recreational fisheries, 

 were not studied as they could not be reliably mapped. The trends study, 

 however, looked at estuarine subtidal and intertidal non-vegetated 

 wetlands, lacustrine wetlands, and palustrine open water and non- 

 vegetated wetlands, all of which may include aquatic bed wetlands. 



Aquatic bed wetlands may be under State ownership and/or State and 

 Federal regulatory jurisdiction in many States, thereby being afforded 

 some level of protection. However, in some States such wetlands may be 

 under private ownership and vulnerable to loss or degradation from 

 dredge or fill projects associated with navigation, marine, gas or oil, or 

 similar projects or activities. Aquatic bed wetlands have diminished 

 substantially in several regions in the U.S. The significant value of this 

 wetland type can not be over-emphasized and priority consideration for 

 acquisition may be warranted based on documentable wetland loss 

 studies. 



The riverine system includes wetlands and deepwater habitats contained 

 within a channel except for wetlands dominated by trees, shrubs, 

 persistent emergents, emergent mosses, or lichens or; habitats with water 

 containing ocean-derived salts in excess of 5 parts per thousand. 

 However, upland islands or palustrine wetlands may occur within the 

 channel. This system has been modified by man's activities through 

 channelization, dredging, encroaching fills and conversion from 

 natural substrate to concrete. Because of such activities, adjacent or 

 intermixed palustrine wetlands have been lost or degraded. 



Riverine wetlands usually are bordered by or intermixed with palustrine 

 wetlands. In many cases, only a narrow band of palustrine wetlands or 



