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Ecosystem valuation is a widely used tool in determining the impact of human activities on an environmental system, by assigning an economic value to an ecosystem or its ecosystem services. ==Value of ecosystem services== The simplest form of ecosystem valuation for orthodox environmental economists is to hold that an ecosystem has a value equivalent to its ecological yield valued as it would be on commodity markets: for the value of water, wood, fish or game, that is purified or nurseried or generated or harboured in that ecosystem. Thus, an exchange value or 'price' is associated with the objects of value, regarded as natural capital, associated with ecosystems and this may be based on the ability of a system to produce yields each year that are exchangeable in operating markets and have existing exchange prices. Economists and some ecologists concentrate on ecosystem services and the assignment of values in a service economy to all that Nature does "for humans" (a basic form of instrumentalism). Work based upon benefit transfer, compiled by ecologist/planner Robert Costanza in the 1990s, has claimed that even just considering the most basic seventeen of these services, the combined value of the ecosystems of the Earth was worth more (US$33T) each year; more than the whole human exchange economy (US$25T) at that time (1995). Other studies have focused on the marginal value of ecosystem changes, as advocated in orthodox economic cost-benefit analysis. In Natural Capitalism, 1999, Paul Hawken, Amory Lovins and Hunter Lovins also advanced an argument to assign a value to the planet Earth in current currency. Ecosystem valuation is far from uncontroversial. Arguments about the non-market valuation of ecosystem can be found by referring to environmental ethics and deep ecology. Mainstream environmental economists have categorized the values that should be assigned to any environmental change for which individuals are willing to pay as follows: * direct use value attributed to direct utilisation of ecosystem services; * indirect use value attributed to indirect utilisation of ecosystem services, through the positive externalities that ecosystems provide; * option value attributed to preserving the option to utilise ecosystem services in the future; * existence value attributed to the pure existence of an ecosystem * altruistic value based on the welfare the ecosystem may give other people * bequest value based on the welfare the ecosystem may give future generations Standard environmental economic methods are used to place a monetary value on ecosystem services where there are no market prices. These include "stated preference" methods and "revealed preference" methods. Stated preference methods, such as the contingent valuation method ask people for their willingness to pay for a certain ecosystem (service). Revealed preference methods, such as hedonic pricing and the travel cost method, use a relation with a market good or service to estimate the willingness-to-pay for the service. Applying such preference based approaches has been criticised as a means of deriving the value of ecosystems and biodiversity and for avoiding deliberation, justification and judgment in making choices.〔(Spash, C.L. 2008. How much is that ecosystem in the window? The one with the bio-diverse trail. Environmental Values, vol. 17, no. 2, 259-284 )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ecosystem valuation」の詳細全文を読む スポンサード リンク
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