Ch. 5— Wetland Trends • 93 



systems that may leaik and support some wetland 

 vegetation, and construction of dikes in coastal 

 areas. 



Saltwater Wetlands 



Saltwater-loss trends differ from those of fresh- 

 water since conversions to deep water and urban 

 use are most prevalent. Agricultural use has had 

 litde impact on saltwater wetlands in recent years 

 (see fig. 8). There was a net loss of 373,000 acres 

 of saltwater vegetated wetlands between the mid- 

 1950's and mid-1970's, representing a 7.6-percent 

 reduction. Emergent saltwater wetlands comprised 

 95 percent of these net losses. The remaining 5 per- 

 cent were saltwater forested and scrub-shrub wet- 

 lands. Information on actual losses and gains is 

 presented below and summarized in table 13. 



Actual losses in saltwater vegetated wetlands 

 totaled 482,000 acres. Conversions to deep water 



were responsible for 55 percent of these losses. This 

 amount probably can be attributed to dredging for 

 canals, port zmd marina development, and erosion. 

 Urban use accounted for 22 percent of the losses. 

 Conversions to nonvegetated types (i.e., unconsoli- 

 dated shore, 1 1 percent; and other, 2 percent) were 

 likely to be associated with dredged-material dis- 

 posal practices, removal of vegetation for recrea- 

 tional development, such as beach creation, and 

 death of vegetation associated with changes in salin- 

 ity. Transitions to freshwater vegetated wetlands 

 were responsible for 6 percent of the losses. Such 

 transitions could be related to increases in fresh- 

 water outflow or dike construction. Agriculture and 

 other uses were each responsible for 2 percent of 

 the losses. 



Actual gains in saltwater vegetated wetlands 

 totaled 109,000 acres. Roughly 50 percent of the 

 gain was from deepwater areas, and 40 percent was 



Figure 8.— Saltwater Wetland Trends (mid-l950's to mid-i970's) 



500 



400 



300 



200 



n~ D 



Actual 

 gain 



(268) 



100 



(107) 



(9) 

 I L 



(2) 



(0) 



(54) 



(62) 



(44) 



(25) 



JUL 



(1) 



(11) (8) 



' ' ' 



Urban 



Agriculture 

 SOURCE USFWS National Wetland Trends Study, 1982. 



Deepwater Nonveg. 



Conversions of wetlands 



Fresh, veg. 



Otfier use 



