1997; Shechter et al., 1998). As a result, recreational values are often estimated using techniques, such as the travel cost method or contingent valuation (Fredman and Emmelin, 2001; Hanley et al., 2003; Herath and Kennedy, 2004). The same techniques can be applied to valuing cultural heritage features within an area visited for recreation (Navrud and Ready, 2002; Sattout et al., 2007). Estimates of the recreational value generated per person-day in a wilderness area are typically on the order of $50 (Walsh et al., 1992; Loomis et al., 1998; Loomis, 2000).

Economic activity associated with use and maintenance of a park or wilderness area generates economic impacts in surrounding communities through public spending on park and wilderness management and maintenance (e.g., employee salaries) and through private spending by visitors in restaurants, hotels, and shops in the course of travel to the park or wilderness area. Property value enhancement refers to the increase in the market value of private property in the vicinity of park, wilderness, or conservation land. Consumption goods produced within the conservation area may be timber in a multi-use national forest or cattle and oysters in a setting such as the Point Reyes National Seashore.

Ecosystem services provided by aquatic and related terrestrial ecosystems generally include nutrient recycling, habitat for plants and animals, flood control, and water supply (NRC, 2004b). The ecosystem service most closely associated with marine estuaries and seagrass beds is nutrient recycling; others include habitat and refuge, food production, and disturbance (i.e., storm or weather) regulation (Costanza et al., 1997). Although ecosystem services are usually not traded in markets, it is possible to estimate their economic value using shadow prices (Kaiser and Roumasset, 2002). The ecosystem resources embodied by Drakes Estero are fairly well understood and are described in the previous chapters (I through VII) of this report. The ecosystem services provided by the specific resources in Drakes Estero have not been quantified in either ecological or economic terms.

Non-use values of wilderness were first formally articulated by Weisbrod (1964), who suggested that undeveloped forest areas might give rise to option value, and by Krutilla (1967), who added the categories of existence and bequest values. First efforts to estimate these values systematically for wilderness areas were carried out by Walsh et al. (1984) in a study of Colorado wilderness areas. Option value is the value attributable to the opportunity at some point in the future to make decisions about the disposition or conservation of an asset (Forsyth, 2000; Bulte et al., 2002; Bosetti et al., 2004; Buttle and Rondleau, 2004). Existence value refers to the non-use value derived by people from the knowledge that something exists, irrespective of whether they (or anyone else) ever make use of it or



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