|Hoagland, P., U.R. Sumaila and S. Farrow, Marine protected areas, In J.H. Steele, S.A. Thorpe and K.K. Turekian, eds., Encyclopedia of Ocean Sciences, London: Academic Press, pp. 1654-1659, 2001|
Zoning the ocean involves the spatial segregation of a marine area in which certain uses are regulated or prohibited. This general definition might apply to any marine area in which some human uses are given preference over others. As the marine counterpart to systems of national and international parks, marine protected areas (MPAs) are conceptually easy to understand and naturally appealing to the public. Yet MPAs differ in important ways from land parks because of their relative inaccessibility, the fugitive nature of fish stocks and the physical transport of pollutants and plankton, the legal characteristics of property rights in the ocean, and the costs of monitoring human activities. MPAs are frequently considered to be a fishery management measure, but they may be used for other purposes as well. We focus on the use of MPAs in the field of fishery management because this use represents one of the most relevant and interesting examples. The extent to which an MPA may be considered an effective management tool depends upon ecological, economic, and distributive management objectives. The economic implications of an MPA depend critically upon the nature of the institutional framework for managing the fishery. Suppose that a fishery supplies only a small part of a large market and that, initially, it is unregulated. Assuming that an equilibrium is reached where harvests balance stock growth, theory suggests, and empirical investigations confirm, that the economic value of the fishery is near zero. Now suppose an MPA is established. A ?refuge effect? implies that the exploitable stock is smaller for any given level of fishing effort. In the absence of any complementary regulation, fishermen will exit the fishery until an open-access equilibrium sets up for the residual exploitable stock. As before, rents are dissipated at this new equilibrium, and no economic value is created through the establishment of the MPA. Over time, a ?stock effect? might lead to an expansion of the exploitable biomass. Again, the existence of economic rents associated with an expanding biomass will attract fishermen until rents dissipate. In the presence of uncertainty, irreversible exploitation, or to meet other policy objectives, MPAs clearly hold promise as a rational way of managing ocean resources, but this promise should not be overstated. In particular, MPAs should not be seen as a panacea to all the problems of fisheries management. Indeed, the best way to see MPAs is probably as a complement to other management tools and measures.