Events & Media

October 14, 2016

It's a Sure Thing: Incorporating Uncertainty into Tradeoff Analysis Can Lead to Better Resource-Management Decisions

In a new study, a team of Bren School researchers demonstrate that accounting for uncertainty about environmental systems and human actions can lead to better management decisions.

Reniel Cabral

The paper, titled “Unexpected Management Choices When Accounting for Uncertainty in Ecosystem Service Trade-off Analyses,” appeared in the Sept. 28 issue of the journal Conservation Letters. Written by lead author and Bren School‒based postdoctoral researcher, Reniel Cabral, and Bren School professors Christopher Costello, Steve Gaines, and Benjamin Halpern, the article describes a study that incorporates uncertainty in an analytical framework used to identify trade-offs in the amount and value of ecosystem services provided under various management scenarios. Read the paper.

Every environmental-management decision involves trade-offs among various uses of resources and the value placed on them by diverse users. To identify optimal solutions, decision-makers increasingly employ an “ecosystem services (ES) decision framework,” an approach that combines natural science and economics to identify the value of services provided by ecosystems under a range of management schemes.

Reniel Cabral: E-mail

A forest may have one value to people who hunt in it or gather food from it, another value to scientists who conduct research in it, and a different value to the owner of a timber company. Coastal residents place a high value on coral reefs, both as important sources of food and as natural sea walls protecting them from storm surges. That same reef may be have a different value to groups seeking tourism dollars, and little or no value to an inland community that does not directly benefit from the services it provides.

The ES decision-framework approach can support managers and policy-makers in identifying optimal outcomes — those providing the greatest amount of ecosystem services while avoiding conflict among diverse stakeholders who value the same resource differently.

The approach is particularly effective at sorting out trade-offs and avoiding conflicts among the increasing number and diversity of stakeholders resulting as new uses are introduced in areas already allocated for other purposes. That can be the case when, to extend the previous examples, a timber company cuts down trees or a traditional fishing ground is closed because it has been newly designated as a scuba-diving area for tourists.

While ES decision framework models are useful in assessing trade-offs resulting from various management strategies, to date, they have largely ignored the inherent uncertainty of natural and human systems. In this paper, the authors show that failing to account for uncertainty can lead to less-than-optimal management decisions, while accounting for uncertainty can improve decision-making.

The authors describe several sources of uncertainty, including the inevitable limits to scientific knowledge about the natural world and a lack of high-quality data sets needed to build accurate predictive models. Human actions and human reactions to information about changes to the resource are another source of uncertainty. For instance, if a fishery were to experience a sudden drop in fish stock, would fishers reduce their fishing effort, fish somewhere else, fish their stocks to depletion, or come up with another approach?

Currently, it is rare for ES trade-off analyses to incorporate uncertainties, either in natural systems (i.e. the unpredictable variability of fish stocks) or human systems (such as the differing values people place on conservation).

The authors show three key findings:

  1. Ignoring uncertainty can lead to substantial losses or missed gains in the provision of ecosystem services.

  2. In a paradox, uncertainty can make stakeholders value conservation despite not preferring it. In the fishery example above, a model that did not account for uncertainty might suggest that to ensure maximum sustainable catch, fishing effort should be pursued at “x” level constantly over time. If conservation were not a priority, that “x” level of fishing would continue even after stocks had decreased, leading to possible collapse of the fishery. But if the model accounts for the uncertainty of stock variability, it would suggest a different, lower, level of fishing in response to the variable stock.

  3. When uncertainties are accounted for, solutions that are less than optimal when not accounting for uncertainty become optimal when accounting for it. As an example, suppose there were two fisheries, one that would provide a constant catch of 90 kilograms a day and another that would have an equal chance every day of providing either 0 or 200 kilograms. Without accounting for uncertainty (embodied in the fluctuating daily yield of the second fishery) and based solely on average yield, a fisher would choose the second option because its average daily yield would be 100 kilograms versus a 90-kilogram daily average for the first fishery. But accounting for uncertainty, a risk-averse fisher might choose the first fishery. Accounting for uncertainty, people could choose different solutions.

“Accounting for uncertainty when analyzing the trade-offs in ecosystem services resulting from various management decisions should expose the risks of those decisions and allow decision-makers to avoid unwanted surprises,” says Cabral.