Science Inventory

Existence Value: Metrics


Ringold, P., D. Peck, T. Angradi, M. Papenfus, Steve Paulsen, Tom Kincaid, AND D. Guignet. Existence Value: Metrics. ACES, Washiington, DC, December 03 - 07, 2018.


Non-use values are the value people place on the existence of an ecosystem. These values describe the ecosystem they don’t expect to directly use or enjoy such as mining or bird watching. Non-use values are much discussed in economic literature and have been shown, in many instances, to be large enough to change the outcome of benefit cost analyses. Despite their importance and an extensive literature on how to assign weights to these values, the literature on the biophysical metrics underpinning these values is not well developed. Biophysical metrics are features that describe the status of an ecosystem. Examples could be the presence of invasive fish, the index of biotic integrity, or the total suspended solids concentration. Uncertainty about these metrics weakens the foundations of benefits analyses as there is doubt over the “good” that people actually value. This research aids EPA in beginning to provide more certainty to the specification of those metrics leading to more certain analysis of the benefits of proposed policy options. This work is part of an ongoing collaboration between natural and social scientists to delineate those biophysical metrics.


While there is a substantial literature on the importance of non-use values, the specification of ecosystem metrics best associated with those values is not well developed. Specification of such metrics is important for communicating the quality of a resource, and in evaluating how a resource change impacts human welfare. Such linked analyses are the foundations for benefit-cost analysis and thus a key element in the formulation of policy. Two opposing constraints make it difficult to comprehensively represent ecosystem quality for non-use values. First, aquatic ecosystems are heterogeneous, making it difficult to fully quantify ecosystem quality with a single or limited set of metrics. Second, respondents to stated preference surveys designed to elicit nonuse values have a cognititive limit to the complexity and number of metrics they can comprehend. Ongoing collaborations between natural and social scientists suggest that metrics of biotic integrity (i. e. metrics representing the degree of departure from conditions expected in the absence of human activity) are appropriate representation of aquatic ecosystems for non-use values. Over the last several decades, aquatic ecosystem ecologists have developed metrics of biotic integrity for differing assemblages and ecosystems consistent with the goals of the Clean Water Act. For example, in surveys that represent large regions of the United States metrics of biotic integrity have been developed for vertebrates and macroinvertebrates for streams and for macroinvertebrates, phyto and zooplankton for lakes. Methods used to develop these metrics include both multimetric indices and metrics estimating the loss of taxa. In quantifying these metrics, biophysical scientists make choices about the spatial units of the representations. Should the data be represented in terms of numbers of lakes or stream length or in terms of stream and lake area? For purposes of economic valuation, this question must focus on how people perceive the resource. Finally, there are also questions about whether the metrics for aquatic resources within a region should be pooled or addressed separately, e.g. one representation for lakes and another for streams. If the status of the ecosystems or their projected responses to changes in stressors is not equivalent among these choices then the choice of metric and its spatial dimension could well make a difference in the formulation of policies. To examine these questions about the appropriate metric and spatial units we calculate aquatic ecosystem status using different methods for a dozen regions in the United States. We evaluate whether the ranks of the regions change with the differing assumptions. We also identify the the magnitude of aquatic ecosystems responses to changes in selected stressors also as a function of varying assumptions. Our analysis is based on data from EPA’s National Aquatic Resources Surveys. Our conclusion is that the differences among assumptions are not equivalent. As a result, we recommend that biophysical and social scientists continue to collaborate and ensure a system of metrics feasible from a biophysical perspective and sensible from the perspective of communicating and estimating non-use values.

Record Details:

Product Published Date: 12/07/2018
Record Last Revised: 12/26/2018
OMB Category: Other
Record ID: 343713