Ch. 5— Wetland Trends • 97 



Table 16.— Percentage of Vegetated Wetland Loss to Different Uses by Physiographic Region^ 



(mid-1 950's to mld-1970's) 



Region Agriculture Urban Other Water/nonvegetated 



1 —Atlantic coastal zone^ 5 36 5 54 



2— Gulf coastal zone<= 1 19 2 78 



3— Atlantic coastal flats" 89 6 2(+) 3 



4— Gulf coastal flats'^ 66 19 4(+) 11 



5— Gulf-Atlantic rolling plain 84 3 4(+) 9 



6— Lower Mississippi Alluvial Plain 90 3 3(+) 4 



7— Eastern higtilands 38 22 5(+) 35 



8— Dakota-Minnesota drift and lake bed flats 83 1 4 (-I-) 12 (+) 



9— Upper Midwest 71 8 3(+) 18 



10— Central 63 5 ^S(+) M ( + ) 



11— Rocky Mountains 71 19( + ) 10( + ) 



12— Intermontane 88 1 7(+) 4(-t-) 



13— Pacific mountains 87 1 7(-l-) 5 



^(-*-) indicates there was a net gain in wetlands from the use category in the region. If (+) is not indicated, then there was a net toss from that use category. 

 Atlantic regions do not include Florida. 

 ^'Gulf regions include Florida. 



SOURCE: Original data from FWS National Wetland Trends Study, 1983. 



exception. Urban use is a source of wetland gain 

 in the West central rolling hills subdivision of the 

 Central region which can be attributed to a gain 

 in wedands in Iowa, accompanied by a slightly 

 lower rate of wetland conversion to urban use in 

 Nebraska. Gains of wetlands from urban use in 

 Iowa could be associated with flood plain manage- 

 ment activities. 



The combined category of deep water, open 

 water, and other nonvegetated types was the sec- 

 ond most important cause of actual losses of vege- 

 tated freshwater wetlands in six of the regions and 

 the third most important cause in the remaining 

 five regions. The proportion of these losses was 

 greater than the national average (10 percent) in 

 five regions. 



These losses to deep water, open water, and other 

 nonvegetated types were accompanied by gains in 

 freshwater vegetated wetlands from these cate- 

 gories, resulting in a net gain in 4 of the 1 1 regions, 

 including Dakota-Minnesota drift and lakebed flats, 

 Central, Rocky Mountains, and Intermontane. All 

 other regions had a net loss of vegetated wetlands 

 from these categories. Subdivision data on these net 

 changes show five exceptions each for the general 

 region trends of net loss and net gain of vegetated 

 wetlands from this category. Again, standard er- 

 rors for these numbers are very high. 



Conversions to other uses were the second most 

 important cause of loss in three regions, the third 

 in four regions, and last in the remaining four 



regions. Proportions of loss from other uses range 

 from 2 to 19 percent. These proportions are greater 

 than the national average (4 percent) in five regions. 

 In all regions, these losses to other uses were accom- 

 panied by gains, resulting in a net gain in fresh- 

 water vegetated wetlands from this category. This 

 gain is relatively small when compared to the overall 

 losses of wetlands. 



Two physiographic regions comprise 98 percent 

 of the data for saltwater wetlands: Atlantic coastal 

 zone and the gulf coastal zone. The remaining 2 

 percent is primarily from the Lower Mississippi Al- 

 luvial Plain. A very small amount of saltwater wet- 

 lands was also measured in the gulf and Atlantic 

 coastal flats regions. No data were coflected for 

 saltwater wetlands of the Pacific coast. 



The Atlantic coastal zone and gulf coastal zone 

 (including Florida) both showed a net loss of salt 

 and brackish wetlands. However, in the Atlantic 

 region, this loss was attributed primarily to urban 

 use. There was also a net loss due to agriculture, 

 conversions to freshwater wedands, and other uses. 

 A net gain of vegetated wedands resulted from deep 

 water, open water, and other unvegetated areas. 

 In the gulf region, the net loss of salt and brackish 

 wedands was due primarily to deep water and non- 

 vegetated areas. Louisiana and Florida accounted 

 for 84 percent and 10 percent of these losses, respec- 

 tively. Erosion, subsidence, and dredging for canals 

 and marinas were probably responsible for these 

 trends. Urban losses also were significant. Addi- 

 tional losses were due to agricultural and other uses. 



