Ecosystem services are the full range of social, ecological, and economic benefits that people obtain from nature. Many US and international agencies have adopted policies that require ecosystem services analyses in planning and decision-making. This paper describes the two fundamental purposes of ecosystem services analyses: 1) describe and measure how humans benefit from ecosystem services (assessment) and 2) use service and benefit measures in tradeoff analyses (decision support). Ecosystem services assessments can be difficult to conduct because forest ecosystems provide many different types of services, service and benefit data are often scarce and incommensurable, and perceptions of many human benefits are normative and context dependent. Frameworks and lists of ecosystem services types are just a starting point for analysis. Measurement problems are being addressed through research, but practical applications of these techniques are difficult. And philosophical concerns, such as the validity of measuring intrinsic values of nature, will persist. A complete accounting of the human benefits of any ecosystem is impossible to attain; assessments can only provide rough estimates of human benefits of ecosystem services. And these measurement issues are compounded when using ecosystem services benefits to evaluate tradeoffs of alternative management scenarios in planning or decision-making.
Ecosystem services assessments are often conducted for a specific ecosystem or landscape (e.g., a wetland or watershed) or jurisdictional unit (e.g., a national park or forest). When using ecosystem services for decision support, managers must further specify the services and benefits to be included in tradeoff analysis. They must identify and prioritize the key services and benefits that are most important in addressing management and policy issues, based on the ecological, social, and economic context of the decision. A tradeoff analysis should be strategically focused on explicit management or policy problems or issues. Issue statements can be based on project purpose (e.g., wetland restoration), environmental or social problems (e.g., climate change), or stakeholder conflicts (e.g., wildlife viewing vs. hunting). Issues help make the analysis manageable by focusing service and benefit metrics and tradeoffs. Using ecosystem services for decision support is a judgement process, not a purely empirical process, and requires collaboration of scientists, managers, and stakeholders. A six step framework for conceptualizing ecosystem service assessments and trade off analyses is presented that includes an iterative set of steps to identify the key services and benefits, analytic tradeoffs, and the final benefit indicators and metrics.