Questions remaining in the quest to quantify ecosystem services
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Ecosystem services provide metrics for quantifying the benefits of nature to humans as well as for measuring the consequences of human actions. For example, how much carbon is sequestered from a wetland mitigation project? How much carbon is released from a wildfire? Communicating the value of ecosystem components and functions in terms of services allows stakeholders to directly understand the intrinsic value of a natural system or compare the benefits and consequences of human activity. A major challenge in operationalizing this philosophy is developing methods of translating variable measures of environmental properties (data) into consistent quantitative estimates of the services they deliver. Ecosystem service estimates incorporate scientific uncertainty, such as sampling uncertainty, modeling uncertainty, and uncertainty associated with knowledge gaps, but also uncertainty in linking a measurable ecosystem property or function to the service it provides. Individual ecological production functions (EPFs) have been developed to answer specific questions in specific contexts, but ecosystem service metrics have not been defined consistently across EPFs in terms of space and time scales, model assumptions, and the portion of an ecosystem service addressed. For example, potential metrics in models quantifying inland wetland ecosystem services include properties like stream nitrogen load, denitrification rate, phosphorus retention, flood mitigation, and a variety of biological metrics (biodiversity, ecological functions supported, population sizes), as well as metrics of recreational benefits (birdwatching, hunting, and wetland aesthetics). Comparing available EPFs is a step towards harmonizing ecosystem service calculation and one difficultly is the different ways to scope and classify environmental properties, not only in terms of using different mathematical functions, inputs, and assumptions, but also in terms of what kind of ecosystem services it estimates. As the global economic community is looking to ecosystem services as a possible mechanism for accounting for the value of nature in business and social decisions, there is a need to understand the precision of ecosystem services estimates. Would two EPFs estimating flood mitigation services for the same area produce comparable estimates, even if they use different input data? This presentation will discuss the challenges we have identified regarding assessing such precision and open discussion for future research priorities.