SPECIAL ISSUE THE VALUES OF WETLANDS: LANDSCAPE AND INSTITUTIONAL PERSPECTIVESValuing the environment as input: review of applications to mangrove-fishery linkages
Introduction
The following paper overviews the general methodology for valuing mangrove-fishery linkages that can be applied to a variety of mangrove and coastal wetland systems found around the world. This approach has been used to assess the economic value of coastal wetland habitats in support of marine fisheries and other ecological functions, such as determining the value of marshlands as habitat for Gulf Coast fisheries in the southern United States (Lynne et al., 1981, Ellis and Fisher, 1987, Farber and Costanza, 1987, Bell, 1989, Freeman, 1991, Bell, 1997) and the value of mangroves for coastal and marine fisheries in Thailand (Sathirathai, 1997) and Mexico (Barbier and Strand, 1998). This approach is consistent with other related studies attempting to analyze habitat-fishery problems more generally, such as analyzing the competition between mangroves and shrimp aquaculture in Ecuador (Parks and Bonifaz, 1994), determining the value of a multiple-use mangrove system under different management options in Bintuni Bay, Irian Jaya, Indonesia (Ruitenbeek, 1994), and examining general coastal system trade-offs, such as the effects of development and/or pollution on habitat-fishery linkages (Kahn and Kemp, 1985, Knowler et al., 1997 Strand and Barbier, 1997; Strand and Bockstael, 1990, Swallow, 1990, Swallow, 1994).
Natural wetlands, including mangroves, provide many important functions for humankind, which can be grouped in terms of direct use, indirect use and non-use values. Fig. 1 summarizes the standard techniques available for assessing the various economic values of wetlands.1 Here, the concern is mainly with indirect use values, i.e. the indirect support and protection provided to economic activity and property by a wetland’s natural ‘services’, or regulatory ecological functions. The ecological function of particular interest is the role of a mangrove or coastal estuarine wetland system in serving as a breeding ground or nursery for off-shore fisheries.
The main technique for valuing this ecological function of a wetland has been called, variously, the production function approach, valuing the environment as input and the value of changes in productivity approach (Freeman, 1991, Mäler, 1991, Barbier, 1994). The basic assumption of this approach is that, because the wetland serves as a breeding ground or nursery for the fishery, this function can be treated as an additional environmental ‘input’ into the fishery. In static approaches, the welfare contribution of this input is determined through producer and consumer surplus measures of changes in the market equilibrium for harvested fish. In dynamic approaches, the wetland support function is included in the intertemporal bioeconomic harvesting problem, usually as part of the growth function of the fish stock, and any welfare impacts of a change in this function can be determined in terms of changes in the long-run equilibrium conditions of the fishery or in the harvesting path to this equilibrium.
The following section reviews both the static and dynamic production function approaches and their suggested applications to the wetland-fishery valuation problem. Two recent case studies of valuing mangrove-fishery linkages are then reviewed. One applies the static methodology in Southern Thailand (Sathirathai, 1997), and the other applies the dynamic model in Campeche, Mexico (Barbier and Strand, 1998).
Section snippets
The production function approach
When a wetland is being indirectly used, in the sense that the ecological functions of the wetland are effectively supporting or protecting economic activity, then the value of these functions is essentially nonmarketed. However, economists have demonstrated that it is possible to value such nonmarketed environmental services through the use of surrogate market valuation, which essentially uses information about a marketed good to infer the value of a related nonmarketed good. Travel cost
Static models
The static approach to valuing wetland-fishery linkages owes its development to a number of studies that have tried to determine the value of marshlands as habitat for Gulf Coast fisheries in the southern United States (Lynne et al., 1981, Ellis and Fisher, 1987, Farber and Costanza, 1987, Bell, 1989, Freeman, 1991, Bell, 1997).
The initial method was first developed by Lynne et al. (1981). Their approach was essentially half-way between the ‘static’ and ‘dynamic’ approaches described in this
Dynamic models
The production function approach can also be incorporated into intertemporal models of renewable resource harvesting in cases where the ecological function affects the growth rate of a stock over time. In such cases, the production function link is a dynamic one, as the ecological function affects the rate at which a renewable resource increases over time, which in turn affects the amount of offtake, or harvest, of the resource. The basic approach to valuation of an environmental input to
A case study of a static model: southern Thailand
Sathirathai (1997) uses the Ellis-Fisher-Freeman model to value the welfare impacts of mangrove deforestation on coastal fisheries in Surat Thani Province on the Gulf of Thailand. In recent decades, the expansion of intensive shrimp farming in the coastal areas of southern Thailand has led to rapid conversion of mangroves. Over 1975–1993 the area of mangroves has virtually halved, from 312 700 hectares (ha) to 168 683 ha. Although the rate of mangrove loss has slowed, in the early 1990s the
A case study of a dynamic model: Campeche, Mexico
Barbier and Strand (1998) employ the dynamic approach to production function analysis to value the role of mangroves in the Laguna de Terminos in supporting the shrimp fishery of Campeche, Mexico.
Mexico’s gulf coast states account for over half of the country's shrimp catch, and the state of Campeche is responsible for one-sixth of Mexico’s total output of shrimp. Campeche’s shrimp fishery employs about 13% of the state’s economically active population. In recent years the total number of boats
Conclusion
This paper has indicated how the economic value of mangroves in supporting coastal and marine fisheries can be estimated through application of production function approaches. Both basic static and dynamic production function models for estimating this value have been reviewed. Case studies of the application of the static and dynamic approaches to valuing the support function of mangroves in Thailand and Mexico have also been examined.
The production function approach appears to be well suited
Acknowledgements
A version of this paper was prepared for the 4th Workshop of the Global Wetlands Economics Network (GWEN), Wetlands: Landscape and Institutional Perspectives, Beijer International Institute of Ecological Economics, The Royal Swedish Academy of Sciences, Stockholm, Sweden, 16–17 November 1997. I am grateful to Jack Ruitenbeek, Tore Söderquist and an anonymous referee for helpful comments. However, the usual caveat applies.
References (25)
- et al.
Theory and estimation of the household production function for wildlife recreation
J. Environ. Econ. Manag.
(1981) The economic value of saltwater marsh supporting marine recreational fishing in the Southeastern United States
Ecol. Econ.
(1997)Valuing environmental resources under alternative management regimes
Ecol. Econ.
(1991)- et al.
Economic losses associated with the degradation of an ecosystem: the case of submerged aquatic vegetation in Chesapeake Bay
J. Environ. Econ. Manag.
(1985) - et al.
Economic value of marsh areas for marine production processes
J. Environ. Econ. Manag.
(1981) Depletion of the environmental basis for renewable resources: the economics of interdependent renewable and nonrenewable resources
J. Environ. Econ. Manag.
(1990)- et al.
Valuing environmental functions in developing countries
Biodivers. Conserv.
(1992) Valuing environmental functions: tropical wetlands
Land Econom.
(1994)- Barbier, E.B., Acreman, M. Knowler, D., 1997. Economic Valuation of Wetlands: A Guide for Policymakers. Ramsar...
- et al.
An economic valuation of wetland benefits