In his thought-provoking commentary, Mark Sagoff documents various pitfalls of economic valuation of ecosystem services. Economic valuation was not central to our study, but we hope that our approach will, among other things, improve economists' ability to value ecosystem services accurately. Our article emphasized the urgent need for ecologists and environmental managers to identify the primarily biotic components of ecosystems that provide services and quantify the characteristics of individual organisms (e.g., population size), functional groups (e.g., trait values), or ecological communities (e.g., vegetation heterogeneity) required to provide the service at a level desired by service beneficiaries.
Despite complications, such knowledge is vital to our understanding of how nature contributes to human society irrespective of the need to place a dollar value on any service. Without this understanding, it is not possible to develop wise management plans or policies to sustain these natural resources. Sagoff argues that service providers may have economic value only if they are under threat and if humans are unable to replace the service readily. We agree that level of threat and availability of alternatives are important in any scheme designed to rank the relative value of services (along with measures of capacity to meet demand, costs of protection, etc.).
Sagoff also suggests that “no one need care about the total value of dung beetle services” because these services are currently not threatened. It is unwise, however, to believe that such services will be ubiquitous in the future (because, e.g., some chemical treatments of internal parasites of cattle have been shown to impact dung beetles negatively) or that it is not necessary to understand their ecological underpinnings. We would argue that it is vital to know how changes in dung beetle populations affect the beetles' capacity to handle cow manure generally, and what supporting systems (e.g., grassland vegetation) are required to ensure that these services continue at the desired level. Well-known examples of the extensive reduction (e.g., bison) or complete extinction (e.g., passenger pigeon) of once common service-providing organisms underscore the necessity of paying attention even to those that are not yet scarce.
It is more likely that many ecosystem services are already under severe threat (MEA 2005), and economic valuation (as well as other methods of quantifying value; e.g., contribution to human health) may be particularly pertinent in these circumstances. For example, almond growers in southern Australia truck in more than 50,000 hives of the European honeybee each year to pollinate their crop, at great financial cost. In the United States, more than a million hives are brought to California annually. In both cases, pollination services from native insects are likely to be limited since much of the native vegetation has been cleared for almond crops. Almond growers would be well advised to explore the cost-benefit trade-offs (at least in dollar terms, if not also including biodiversity benefits) of implementing land-management strategies to support native pollinators, particularly given massive and still poorly understood die-offs of honeybees on several continents.
Sagoff points out that environmental economists have traveled “a long and weary road” in their attempts to value nature. Too few ecologists have traveled this road with them. It's past time for ecologists and economists to travel a new valuation road together, and to pick up sociologists and psychologists along the way.
