This article demonstrates an approach to Multi-Criteria Decision Analysis that compares non-monetary ecosystem service (ES) outcomes for environmental decision making. ES outcomes are often inadequately defined and characterized by imprecision and uncertainty. Outranking methods enrich our understanding of the imperfect knowledge of ES outcomes by allowing decision makers to closely examine and apply preference measures to relationships among the outcomes. We explain the methodological assumptions related to the Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE) method, and apply it to a wetland restoration planning study in Rhode Island, USA. In the study, we partnered with a watershed management organization to evaluate four wetland restoration alternatives for their abilities to supply five ES: flood water regulation, scenic landscapes, learning opportunities, recreation, and birds. Twenty-two benefit indicators were identified for the ES as well as one indicator for social equity and one indicator for reliability of ES provision. We developed preference functions to characterize the strength of evidence across estimated indicator values between pairs of alternatives. We ranked the alternatives based on these preferences and weights on ES relevant to different planning contexts. We discuss successes and challenges of implementing PROMETHEE, including feedback from our partners who utilized the methods.
Keywords: MCDA; PROMETHEE; ecological restoration; ecosystem services; preferences.