of wetlands is presented, and trends from recent 

 data are examined. Salient characteristics of re- 

 maining wetlands are described and their physical 

 potential for agricultural conversion assessed. The 

 economics of converting wetlands for farm program 

 crop production are analyzed with and without 

 farm program benefits. The effects of incentives for 

 conversion provided by the Federal income tax 

 code are discussed. A description of wetland values 

 foregone by conversion to cropland is followed by 

 an analysis of farming potential in critical wetland 

 problem areas. The report ends with conclusions 

 and implications for policy. 



Extent and Location of Wetland 

 Conversion 



Estimates of historiceil wetland acreage in the 

 United States range from 127 million acres (45) to 

 185 million acres (28). Comparing these estimates to 

 the best current estimate of 99 million acres of re- 

 maining wetlands (13) reveals a loss of 22 to 46 per- 

 cent of the original wetland acreage that European 

 settlers found on arriving here. There are a variety 

 of data estimating wetland acreage at various times, 



none of it uniform in scope or definition (see app. 1). 

 Despite the flawed nature of these data for assess- 

 ing trends, a review of the different estimates pro- 

 vides useful background to the problem of wetland 

 conversion. 



Long-term Trends 



The U.S. Congress gave 64.9 million acres of 

 wetlands to 15 States in the Swamp Land Acts of 

 1849, 1850, and 1860. Comparison of recent 

 estimates of wetland acreage in these States in- 

 dicates that 19 percent of this acreage was lost by 

 the mid-1970's (table 1). Six of the 15 States ap- 

 peared to have added 8.9 million acres of wetlands 

 between 1849 and the mid-1970's, but this probably 

 reflects incomplete accounting for all wetlands 

 under the acts. The remaining nine States lost 21.3 

 million acres, or 40 percent of their wetlands. 



The first national wetlands inventory, conducted in 

 1954, estimated 74.4 million acres of wetlands, 

 classified according to 20 types (38). In 1979, a 

 more comprehensive analysis using aerial 

 photographs estimated that there had been 108.2 

 million acres of wetlands in the 1950's [13). 



c 



Wetland Terms 



• Hydric soil: A soil ". . .that in its undrained 

 condition is saturated, flooded, or ponded long 

 enough during the growing season to develop 

 anaerobic conditions that favor the growth and 

 regeneration of hydrophytic vegetation" [48]. 



• Wetland systems: Wetlands and deepwater 

 habitats that share the influence of similar 

 hydrologic, geomorphologic, chemical, or 

 biological factors. Five major systems are 

 recognized (see [8] for details): 



Marine— Open ocean overlying the continen- 

 tal shelf and its associated high-energy 

 coastline. 



Estuarine—Deepv/ateT tidal habitats and adja- 

 cent tidal wetlands that are usually partly 

 enclosed by land but have open, partly 

 obstructed, or sporadic access to the open 

 ocean, and in which ocean water is at least 

 occasionally diluted by freshwater runoff 

 from the land. 



Riverine— Ml wetlands and deepwater 

 habitats contained within a channel, except 

 for wedands dominated by trees, shrubs, per- 

 sistent emergent plants, mosses, or lichens, 

 and habitats containing ocean-derived salts 

 above 0.5 o/oo (parts per thousand). 



Lacustrine— Y/etlands and deepwater habitats 

 with all of the following features: 1) situated 

 in a topographic depression or a dammed 

 river channel; 2) lacking trees, shrubs, and 

 persistent emergent plants, mosses, or lichens 

 covering more than 30 percent of the area; 

 and 3) with a total area exceeding 20 acres. 



PaluBtrine—M\ nontidal wetlands dominated 

 by trees, shrubs, and persistent emergent 

 plants, mosses, or lichens, and all such 

 wedands that occur in tidal areas where 

 salinity due to ocean-derived salts is below 

 0.5 o/oo (parts per thousand). 



Pocosin wetland (the name is derived from an 

 Algonquin word meaning "swamp on a hill"): 

 These wetlands are unique to the southeastern 

 coastal plain from Virginia to northern Florida. 

 They lie in broad, flat upland areas away from 

 large streams and are covered by evergreen 

 forest and scrub-shrub vegetation [32, 43). 



Prairie pothole wetland: These wetlands were 

 formed from melting ice fragments in glacial 

 times. They are widespread shallow depres- 

 sions, mostly less than 2 feet deep and varying 

 from less than one to several hundred acres 

 [43]. Many potholes are only seasonally wet 

 and can resemble dry land in periods of 

 drought. 



c 



