The concept of cumulative effect assessment (CEA) as a theory and tool for the quantitative assessment of cumulative effects (impacts) on multifunctional wetlands was furthered in view of a an inherent and chronic lack of environmental data sets in the vast majority of ecosystems in the developing Asia that is a major stumbling block on the way of CEA. Whereas expert opinion as a CEA method has been long recognized, a participatory rural appraisal (PRA) as another important method was largely overlooked despite its strong validity under the circumstances when the required environmental data...