It's a thin line between priceless and worthless (original article was a .pdf, which I hate, so here's a Google-cached html).

Ecosystems services to humans can somtimes be simply assessed, as in the case of fish harvested from the sea, but in other instances may be indirectly enjoyed in ways that can be complex and difficult to determine. Management based on ecosystem services requires a full understanding of the complex ways in which these services benefit humans. The valuation of ecosystem services is also necessary for the accurate assessment of the trade-offs involved in different management options. Valuation can be expressed in economic terms in many instances, using an expanding set of practical valuation techniques. These valuations should reflect the significance or importance of the ecological service categories, and ideally the valuations of unit changes in the levels of those services across management options. When unit valuations based on ratio or interval scales are not feasible, practical methods of scoring, ranking, or rating can be used in combination with assessments of the changes in service flows.

By refusing to apply standards of economic value to the services nature provides, we end up not avoiding all comparisons based on economic considerations, but rather assuming that the natural system has value only as raw resources. Making explicit those values helps us make rational decisions.

"The situation in New Orleans is classic," said Farber, who was on the National Academy of Sciences panel that reviewed Louisiana's coastal restoration plan, both before and after the disaster. "Before Katrina, everyone was saying that there were not enough wetlands to protect the city. A crude 'rule of thumb' is that three miles of wetlands will reduce storm surges by one foot, and that an acre of wetlands provides roughly $20,000 worth of services. But that same acre would sell for only $500. The gap between market value and social value is huge…if everything in the grocery store was free, we'd walk out with it all. Markets, then, cannot be relied upon to preserve resources of great social value, such as wetlands."

I'm not entirely sure that Farber's conclusion that "markets...cannot be relied upon to preserve resources of great social value" is complete. It is true, I think, but it is also true that government projects can destroy the very areas they were created to protect. It's an issue where neither the privitisation nor the centralized control of an asset is always correct, but rather one in which the only right action is the action that is right for this particular instance. No general rules, no easy answers.

Via Eurekalert.