Ch. 5— Wetland Trends • 91 



convert wetsoils to other uses than wetlands), then 

 the percentage of wetsoils that were reclaimed wet- 

 lands prior to the mid-1950's was 60 percent at 

 most. If we then assume that at most 60 percent 

 of the 135 million acres of reclaimed lands reported 

 by Wooten were wetlands and add NWTS's esti- 

 mate of 104 million acres of wetlands in the mid- 

 1950's, we can derive a maximum value for "origi- 

 nal" wetlands of 185 million acres. 



Thus, previous estimates of loss of original wet- 

 lands probably were low. If the SCS estimate of 

 127 million acres of original wetlands is accepted, 

 then losses may have been as low as 30 percent. 



If only one-third of the reclaimed lands were wet- 

 lands, as was assumed for the purposes of Circular 

 39, then there was an original acreage of 149 mUlion 

 acres for a loss of nearly 40 percent. If at most 60 

 percent of the reclaimed lands were wetlands (as 

 a means of developing a maximum estimate of 185 

 million acres of original wetlands), then as much 

 as 50 percent of the original wetlands may have 

 been converted. All of these estimates are limited 

 by the lack of good data on the amount of land that 

 has been drained or otherwise reclaimed and the 

 relationship between wetlands and wetsoils. 



VEGETATED WETLAND TRENDS 



Freshwater Wetlands 



Since freshwater areas comprise 95 percent of the 

 Nation's vegetated wetlands, freshwater wetland 

 losses are similar to overall national trends (see fig. 

 7). There was a net loss of 11 million acres of 

 freshwater vegetated wedands between the mid- 

 1950's and mid-1970's, representing a reduction 

 of 1 1 percent. Forested wetlands accounted for 54 

 percent of the net loss of freshwater vegetated wet- 

 lands, emergent marshes accounted for 42 percent, 

 and scrub-shrub wetlands accounted for 4 percent. 

 Information on actual losses and gains are presented 

 below and summarized in table 12. 



Actual losses of freshwater vegetated wetlands 

 totaled 14.6 million acres. Agricultural land use was 

 responsible for 80 percent of these losses. The re- 

 maining 20 percent was comprised of urban use (6 

 percent), other use (4 percent), nonvegetated habi- 

 tat (open water, 4 percent; unconsolidated shore, 

 1 percent; and other nonvegetated habitat, less than 

 1 percent), deepwater types (4 percent), and salt- 

 water vegetated wetlands (less than 1 percent). 

 These losses to nonvegetated open water and deep 

 water are most likely associated with impoundments 

 (e.g., farm ponds, water supply, flood control and 

 recreational reservoirs, and waterfowl-management 

 impoundments). They also could be associated with 

 drainage practices that concentrate water in the 

 lowest lying wedand to allow drainage of other wet- 



lands in the watershed. Factors associated with the 

 loss to unconsolidated shore might also be associated 

 with impoundments, especially if water levels fluc- 

 tuate. Other possible factors responsible for such 

 loss include grazing, plowing, and natural climatic 

 shifts associated with reductions in wedand vegeta- 

 tion. Losses to saltwater wetlands may result from 

 decreased freshwater outflows or destruction of 

 dikes in coastal areas. 



Actual gains in freshwater vegetated wetlands 

 totaled 3.6 million acres. Roughly 50 percent of the 

 gains were from the "other uses" category. These 

 gains can be accounted for primarily by increases 

 in emergent and scrub-shrub wedands surrounding 

 newly constructed farm ponds on lands that were 

 formerly neither wetlands nor in agricultural use. 

 According to information from SCS, about 50,000 

 farm ponds, averaging 0.5 acre in size, were con- 

 structed each year during the period analyzed in 

 NWTS (18). Other gains were from agriculture (25 

 percent), nonvegetated types (13 percent from open 

 water and 2 percent from unconsolidated shore), 

 deep water (8 percent), urban areas (1 percent), 

 and saltwater vegetated wedands (1 percent). Most 

 of these gains probably were related to successional 

 changes associated with abandonment of former 

 land uses, such as the lack of maintenance of drain- 

 age ditches for forestry and agriculture, or natural 

 factors like beaver activity, construction of roads 

 that block drainage, construction of irrigation ditch 



