Making water ecosystem services count: a purpose-driven systematic literature review of economic valuation

This systematic literature review examines the economic valuation of water ecosystem services (WES) through a purpose-driven perspective, relating valuation methods and value concepts to the stated purposes for which monetary evidence is produced. A total of 137 peer-reviewed studies were analyzed, categorized by valuation method, geographic distribution, ecosystem type, value concept, and policy purpose. The review reveals a strong concentration of research in North America and Asia, while freshwater ecosystems represent the main empirical focus of WES valuation. Recurring gaps include limited treatment of ecosystem service bundles, infrequent use of biophysical information within monetary estimation and causal policy-evaluation designs, underrepresentation of option and non-use values, and few studies directed toward ecosystem or natural capital accounting. The review further shows that valuation methods are not used uniformly across purposes: planning-oriented studies draw on a broad mix of approaches, ex-ante appraisal relies mainly on stated preference methods, and accounting-oriented applications primarily use cost- and market-based methods. By relating valuation choices to their intended use, the review provides a basis for interpreting WES monetary evidence according to whether the objective is strategic planning, policy appraisal, or ecosystem accounting.