22. York, D.W., B.C. Dysart, III, and L.W. Gahan. 1977. Modeling multiple- 

 use in natural areas: part II--the Santee Swamp study. Water Resources 

 Bulletin 13(2):283-295. 



This paper presents a management-oriented activities model designed for 

 maximizing the market and nonmarket social benefits conferred by the Great Santee 

 Swamp of South Carolina. This 18,000-acre bottomland hardwoods region was the 

 subject of controversy stemming from a proposed timber harvesting contract. The 

 timber harvesting activity would (according to environmentalists) diminish the 

 amenity values from various recreational activities pursued on the swamp, 

 including hunting and fishing. The swamp offers striped bass, largemouth bass, 

 crappie, and bream fishing to the sportsman. Duck hunting was reputed to be 

 excellent in the late 1970's. 



Numerical parameters were estimated for a net benefits model that included 

 the market prices of the timber yield, option values (for nonmarket outputs), 

 interaction effects between recreational activities and timber harvesting, 

 regional income and employment multiplier effects, and suitable cost terms. Some 

 timber harvesting was socially optimal according to the activities model, but 

 the optimal harvesting rate was only 64% of that proposed in the timber 

 harvesting contract. The optimum management activity strategy was relatively 

 insensitive to perturbations of the option values and interaction effects, but 

 quite sensitive to the values chosen for the regional income and employment 

 multipliers. 



23. Batie, S.S., and J.R. Wilson. 1978. Economic values attributable to 

 Virginia's coastal wetlands as inputs in oyster production. Southern 

 Journal of Agricultural Economics 10(1) :111-118. 



Batie and Wilson attempt to quantify the habitat provision benefits 

 provided by coastal wetlands in the commercial harvesting of oysters. Batie 

 and Wilson estimate the marginal value product of coastal wetland acreage in a 

 cross-section regression model in which the weight of the 1969 harvest by the 

 17 Virginia coastal counties is the dependent variable. The independent 

 variables are the 1969 harvest effort for each of the 17 coastal counties, number 

 of acres of leased oyster grounds by coastal county in 1969, number of acres of 

 open access property oyster grounds (by coastal county in 1976), number of 

 coastal wetland acres (by county in 1969), and a dummy variable to represent 

 salinity levels. 



Some of the assumptions underlying the model include: (1) oysters are 

 presumed to be harvested in waters adjacent to the counties where the harvest 

 data are reported; (2) all of a county's wetlands contribute uniformly to the 

 production of oyster biomass, and harvest is solely determined by effort and 

 biomass production; (3) the effort variable is adequately quantified by adding 

 together the number of oyster tongs in a county and the number of oyster dredges 

 and multiplying the sum by a constant (0.52688); and (4) the variation in oyster 

 harvesting man-hours across counties is nil. 



Oyster biomass produced in any year is a function of many variables, 

 including water temperature, disease levels, predator pressure, water quality, 

 and salinity. Also, the relation between wetlands and oyster biomass is complex. 



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