Moral values that people attach to species are quite high. Responses to questionnaires have indicated that people place a surprisingly high value on just the knowledge that a thing exists independent of any use (Randall, 1986, and Chapter 25 of this book). Economists, using a method called contingent valuation, create shadow markets in which they can ask people how much they would be willing to pay to protect a species, quite independent of any use of the species (see Chapter 25). If existence values can be thought of as a rough indicator of moral values for present purposes, we can say that species also have considerable moral value, measurable in dollars.

So, we can say with some confidence that some species have considerable commodity, amenity, and moral value. The problem that economists have encountered is that these values are distributed very unevenly among species, at least given our current knowledge. For example, Hanemann and Fisher (1985) have surmised that under certain assumptions, a wild grass recently discovered in Mexico, a perennial related to corn, may prove to have a value of $6.82 billion annually, and they calculated its value for only one possible use—the creation of a perennial hybrid of corn (Fisher and Hanemann, 1985; see also Chapters 10 and 11 of this volume).

At present, however, we do not have sufficient knowledge to calculate the value of most species. Consequently, in addition to the known values that economists note with respect to some small number of species, they also calculate an option value for species of unknown worth, i.e., the value we should place on the possibility that a future discovery will make useful a species that we currently think useless (Fisher and Hanemann, 1985; see also Chapter 25 of this book). If we extinguish a species now, such discoveries are precluded. Fisher and Hanemann therefore define option value as the present benefit of holding open the possibility that some species we might eradicate today may prove valuable in the future. They would ask people how much they are willing to pay to retain the option of saving the species, given the possibility that new knowledge indicating its value may be discovered in the future.

One important aspect of option value is that it applies equally to commodity, amenity, and morality. As time passes, we gain knowledge in all of these areas, and new knowledge may lead to new commodity uses for a species or to a new level of aesthetic appreciation, or our moral values may change and some species will, in the future, prove to have moral value that we cannot now recognize.

If placing a dollar figure on these option values seems a daunting task, the situation is actually far worse than it first seems. Calculations of option value can only be begun after we identify a species, guess what uses that species might have, place some dollar value on those uses, and estimate the likelihood of such discoveries occurring at any future date (so that we can discount the values across time). Once we’ve done all that, we can try to figure out how to translate those future, possible values into present dollars. I think it is safe to say that despite the great theoretical interest in assigning use and option values to species, and some impressive strides in modeling these formally, it may be a long time before the total value of even one species can be stated in terms of present dollars (Norton, in press).

It is worth stepping back to look at the most difficult problems faced by the divide-and-conquer method. First, there is the problem of irreversibility. In general,

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