The Alaskan wilderness may be worth funding for people who consider wild open spaces, polar bears and migrating herds of caribou important, but will never travel to Alaska. Survey approaches are often the only way to ascertain non-use values, although many experts note that surveys can provide questionable results. Still, researchers and managers view the results as at least a gauge for valuing a natural resource.
Replacement costs, like calculating the cost of preserving land in the New York City watershed versus building a filtration plant, make easy comparisons, but only tell part of the story. Avoided costs are estimates of how much money would be spent if services had to be purchased. The value of natural pest control, pollination, flood control, soil fertilization, and water filtration are hard to calculate, because actual expenditures are avoided if the natural ecological services are intact and functioning properly. As a result, the risk and degree of a malfunctioning natural service and the projected cost of a technological fix must be estimated. The Hedonic property value method uses the prices of residential property to reveal the value of local environmental attributes. This method is limited to environmental services that are located near residential areas. Property values tend to increase if they're located near a lake or urban water amenity, or if the water quality of streams and lakes improves locally. Homeowners appear to place a value on at least the aesthetics of a wetland, although some homeowners also probably appreciate the flood control and water quality benefits of wetlands.
The traditional valuation techniques described above attempt to assign value to nature and its services. Jim Salzman, a professor at Washington College of Law, American University, notes that although these methods provide a common currency to measure nature's worth, they fail to capture the true value of ecosystems services. In addition, many of these valuation techniques also are expensive to calculate. They may require extensive survey development, questionnaire distribution, and follow-up.