scientists as inflexible and simplistic. These scientists propose to measure 

 the value of wetlands by the dollar value of the fossil fuel equivalent of the 

 solar energy that the wetland converts to plant biomass. This is clearly not 

 a statement about observable human economic activities, nor does it purport to 

 be a statement about hypothetical human behavior under certain interesting, 

 relevant circumstances. Thus when certain wetlands scientists talk about value, 

 they use the term in a remarkably different fashion from that employed by 

 economists and social scientists, who use the term to refer to individual and 

 societal choices in the context of a universe with a great diversity of 

 commodities but limited private and social resources. 



One broad generic theme that is readily recognized in all of the literature 

 discussed here is the distinction between total and marginal values. Many works 

 discussed in this bibliography cope with the inherent diversity of the subject 

 by focusing on one type of wetlands and imputing values to a broad panoply of 

 functions for this class of wetlands. However, one type of function often 

 dominates other socially useful outputs for any given class of wetlands. For 

 the prairie potholes, say, this dominant function is probably breeding and summer 

 habitat provision for migratory waterfowl. And in the prairie pothole region, 

 the principal cause of wetlands loss is farmland drainage and conversion. Thus 

 within this diversity a number of readily recognized social and biological themes 

 emerge to orient the wetlands specialist as well as the general field biologist. 



To their credit, economists doing research in imputing values to wetlands 

 have often recognized the complex nature of wetlands and have shaped their 

 research activities to incorporate the geological, hydrological , and biological 

 diversity of these land forms. This partly accounts for the fact that one of 

 the apparent gaps in the literature is the absence of generic theories of 

 wetlands values that encompass a wide range of wetlands types. 



Some of the major wetlands types include glaciated prairie potholes, 

 bottomland hardwood swamps, coastal salt marshes, coastal estuarine zones, playa 

 lakes, and riparian zones of the arid western U.S. Not all wetlands perform 

 all of the functions that ecologists, economists, and environmentalists allege 

 to be beneficial to man. Among these functions are the provision of fish and 

 wildlife habitat, geochemical cycling, sediment trapping, contaminant removal, 

 flood prevention, erosion control, climatological stabilization, groundwater 

 recharge and storage, habitat for endangered and rare flora and fauna, recreation 

 and aesthetic benefits, and opportunities for scientific research. In addition, 

 there are certain commercial economic activities that are heavily contingent on 

 wetlands preservation, including timber and shellfish harvesting. 



Not only is the distribution of these functions and values among various 

 wetland types quite irregular, there is too little recognition among economists 

 and the environmentally minded public that certain functions clash with others. 

 For example, selective or clearcutting of timber stands may yield a modest 

 positive pecuniary return. It can also, in certain situations, limit the spread 

 of infectious diseases. However, diseased stands might provide wildlife habitat 

 of the same or better quality as healthy stands, while clearcutting involves the 

 loss of valuable wildlife habitat and important aesthetic amenity values. Thus 

 the provision of some outputs by selection of management decision variables 



IV 



