Approaches for Aggregating Preferences in Participatory Forest Planning - An Experimental Study

Many forest planning situations are complex; multiple criteria of different natures have to be considered and several stakeholders or social groups may be involved. An approach that is increasingly used in these complex situations is the combination of multiple criteria decision analysis (MCDA) and participatory planning. A crucial part of MCDA processes involving more than one decision maker is the aggregation of individual stakeholder preferences into a collective preference; in a participatory context, the aggregation mechanism should be equitable and transparent so as to create trust in the process. This study evaluates three approaches for the aggregation of stakeholders’ preferences in a participatory MCDA process: extended goal programming (EGP), the weighted arithmetic mean method (WAMM), and the geometric mean method (GMM). The aggregation approaches were tested in a role playing exercise with students. The approaches have different properties and result in different rankings, thus the main conclusions are that the choice of aggregation approach should depend on the situation and the stakeholders. Moreover, if aggregation methods are used in participatory planning, they should be used as tools for exploring and increasing knowledge about the issue rather than as methods that produce “the optimal solution”.