The 1977 National Resources Inventory (NRI), by 

 USDA's Soil Conservation Service, used the 1954 

 classification system. Only wetland types 3-20 on 

 non-Federal land were counted, even though most 

 agricultural conversion of wetlands occurs in the 

 seasonally flooded basins and flats and inland fresh 

 meadows of types 1 and 2. A total of 41.5 million 

 acres of non-Federal wetland types 3-20 were inven- 

 toried; USDA estimated that an additional 29 

 million acres of types 1 and 2 remained in 1977, for 

 a toted of 70.5 million acres of wetlands. 



A more recent NRI in 1982 counted 78.4 million 

 acres of non-Federal wetlands of which 44.5 million 

 acres were in types 3-20, an increase of 3 million 

 acres over the 1977 estimate. The 1982 inventory 

 counted 31.7 million acres of wetland types 1 and 

 2, about 40 percent of the total. If wetland types 1 

 and 2 were in roughly the same proportion in 1977, 

 the 41.5 million acres of types 3-20 imply a total of 

 69.2 million acres of non-Federal wetlands. Allow- 

 ing for higher losses of types 1 and 2, the original 

 estimate of 70.5 million acres of non-Federal 

 wetlands in 1977 appears reasonable. 



Using a statistical sample of wetlands identiHed 

 from aerial photographs, the U.S. Fish and Wildlife 

 Service (FWS) estimated that 99 million acres of 

 wetlands remained in the mid-1970's. The 1982 NRI 

 counted 78.4 million acres of non-Federal wetlands 



Table 1 — Patented swamplands and remaining 

 wetlands, 1849 and mid-1970's 



remaining in 1982. The 20.7-million-acre difference 

 is partly wetlands in Federal ownership and partly 

 additional losses of wetlands since the mid-1970's. 



Estimates of federally owned wetlands are surpris- 

 ingly difficult to obtain. The Fish and Wildlife Ser- 

 vice controls 32 million acres of palustrine 

 wetlands and 2 million acres of estuarine wetlands; 

 however, only 5 million acres are in the continental 

 United States, with the remaining majority in 

 Alaska (43). Estimates of Federal wetland holdings 

 collected by Dale Pierce of the Department of In- 

 terior (table 2) show 12.5 million wetland acres 

 under Federal ownership or lease in the lower 48 

 States. Without better data for Federal wetland 

 acreage, however, no estimate of losses between the 

 mid-1970's and 1980's is possible from these 

 sources. 



The various estimates of wetland acreage discussed 

 here and in appendix 1 are summarized in figure 1. 

 Rates of wetland conversion implied by the 

 estimates vary widely from period to period. Be- 

 tween 1850 and 1919, wetland conversion ranged 

 from 193,000 to 1 million acres per year. Between 

 1919 and the mid-1950's, conversion slowed to a 

 rate of 177,000 acres per year. An average of 

 460,000 acres of wetlands were lost each year be- 

 tween the mid-1950's and the mid-1970's. No 

 estimate of total Federal and non-Federal wetlands 

 exists for 1982, so a conversion rate cannot be 

 calculated. 



The firmest conclusion that can be drawn from 

 these data is that the highest rate of wetland loss 

 since the turn of the century occurred in the 1960's 

 and 1970's. Wetland conversion rates have probably 

 been somewhat lower since the end of the 1970's 

 [28], but there are few data to support this 

 assertion. 



Table 2— Estimated Federal wetland holdings, 1985 



• = Fewer than 100,000 acres. 



'Wetlands given to States by congressional action. Not all 

 original wetlands were patented in all States [38]. 

 V3]- 



'Excludes 29 million acres of Alaskan wetlands (43). 

 'Excludes 9 million acres of Alaskan wetlands. 

 Source: Dale Pierce, Dept. of Interior. 



