96 • Wetlands: Their Use and Regulation 



Table 15.— Pattern of Wetland Loss by Physiographic Region 



Wetland portion New loss of Standard 



of region wetlands (mid- Actual Actual error for 



(mid-1950's) 1950's-mid-1970's loss gain net change 



Region (%) (%) (acres) (acres) (%) 



1— Atlantic coastal zone^ 16 3 84,000 48,000 52.3= 



2— Gulf coastal zone" 28 9 371,000 70,000 11.3" 



3— Atlantic coastal flats^ 36 11 1,274,000 74,000 15.0® 



4— Gulf coastal flats" 27 13 1 ,872,000 341 ,000 14.5' 



5— Gulf-Atlantic rolling plain 8 13 2,310,000 291,000 31.29 



6— Lower Mississippi Alluvial Plain . 36 32 3,749,000 331,000 8.6^ 



7— Eastern highlands 2 2 322,000 211,000 68.89 



8— Dakota-Minnesota drift 



and lake bed flats 10 9 816,000 424,000 33.69 



9— Upper Midwest 8 7 2,286,000 754,000 16.89 



10— Central 1 3 763,000 637,000 (i) 



11— Rocky Mountains 4 <1 125,000 112,000 (i) 



12— Intermontane 1 12 685,000 320,000 (i) 



13— Pacific mountains 1 31 473,000 94,000 77.1 



^Atlantic regions do not include Florida. 



Gulf regions include Florida. 

 ^Standard error given is for saltwater wetlands. The fresfiwater wetlands had a net gain of 10,626 acres witti a standard error of 86.9 percent. 



Standard error given is for saltwater wetlands. Tfie freshwater wetlands had a net gain of 2,137 acres with a standard deviation greater than this value. 

 ^Standard error given is for freshwater wetlands. Saltwater wetlands had a net loss of 866 acres with a standard deviation greater than this value. 



Standard error given is for freshwater wetlands Saltwater wetlands had a net gain of 933 acres with a standard error of 81.6 percent 

 9standard error is for all vegetated wetlands measured in region which included exclusively freshwater types. 

 . Standard error is for freshwater wetlands. Saltwater wetlands had a net loss of 22,282 acres with a standard error of 67.8 percent, 

 'standard deviation is greater than estimated net change. 



SOURCE: Original data from f=WS National Wetland Trends Study. 1983. 



per Midwest. Two regions have a lower propor- 

 tion of land area as wetlands and loss rates greater 

 than the national average: Pacific mountains and 

 Intermontane. Three regions have a lower propor- 

 tion of land area as wedands and loss rates less than 

 the national average: Eastern highlands, Central, 

 and Rocky Mountains. Although the amount of 

 wedand acreage lost from these areas with relatively 

 few wetlands may not have contributed much to 

 the national totals, such losses may be environmen- 

 tally significant on a regional level. 



The percentage of wetland loss to various activi- 

 ties varies among the physiographic regions (see 

 table 16). The actual losses of vegetated freshwater 

 wetlands to agriculture range from 1 to 90 percent. 

 However, agricultural use was the greatest cause 

 of loss of vegetated freshwater wetlands in all 

 regions, and the proportion of agricultural loss was 

 greater than the nationEil average (i.e., 80 percent) 

 in six regions. 



In all 11 physiographic regions with predom- 

 inandy vegetated freshwater wedands, the losses to 

 agriculture were greater than any gains in wedands 

 from agriculture. However, there were two excep- 

 tions to this net loss to agriculture when data from 



subdivisions comprising the physiographic regions 

 were examined. (Standard errors are extremely 

 high for subdivision data.) Agriculture is a source 

 of net gain of wetlands in the Adirondack-New 

 England subdivision of the Eastern highlands re- 

 gion. This trend is supported by the findings of the 

 New England case study, which notes increases in 

 wetlands from agricultural abandonment and the 

 lack of maintenance of drainage ditches. Agricul- 

 ture is also a source of net gain of wetlands in the 

 Columbia Basin subdivision of the Intermontane 

 region. Wetland increases associated with irriga- 

 tion development may be partially responsible for 

 this trend. 



Conversions to urban use were the second most 

 important cause of actual losses in two regions, the 

 third most important cause in three regions, and 

 the least important cause in six regions. Propor- 

 tions of loss to urban use range from to 36 per- 

 cent. These proportions are greater than the nation- 

 al average (6 percent) for urban loss in three re- 

 gions: gulf coastal flats. Eastern highlands, and Up- 

 per Midwest. 



In all regions, losses to urban use were greater 

 than any gains in wetlands from this use, with one 



