Ecosystem services and environmental decision making: seeking order in complexity.

The Ecosystem Service Paradigm (EsSP) is increasingly a component or even an underlying principle of environmental policy, legislation and management internationally. The EsSP can be used to define links between human activities and ecosystems, and ecosystems and the services that in turn support and sustain those and other activities; this information can then be used to evaluate, justify or optimize decisions. However, how EsS within various practical applications and frameworks are applied, defined, quantified, modelled, valued and communicated ranges widely, potentially hindering their roles as cross-sectoral tools. For this paradigm to be useful for cross-disciplinary integration, it is important that practitioners in different fields are clear about what is meant and assumed when terms are used, and within what context assessments are being carried out. The logic behind practical applications of the EsSP can be explained by the EsS Decision Cascade, a three-part, iterative conceptual framework. Within the decision cascade, Ecosystem Service Decision Analysis (EsSD) defines the proposed policies or actions (scenarios), and the changes/pressures under consideration in different scenarios. Within the context laid out by EsSD, Ecosystem Service Assessment (EsSA) will then evaluate how such changes affect biophysical structure, and thus ecosystem function and services; Ecosystem Service Valuation (EsSV) then takes the results from these analyses and generates valuations to inform decisions; linking back to EsSD. EsS-based evaluations can expand the current risk-focused thinking behind ecological risk assessment (ERA) to consider trade-offs between a range of desirable and undesirable responses of a variety of ecosystem endpoints; such an assessment can be termed an Ecosystem Response Assessment (EcoResA), or if applied in a spatially explicit manner, an Ecosystem Regional Assessment (EcoRegA); understanding of such trade-offs is essential to inform decisions about more sustainable remediation, regulation and management of landscapes and resources. This paper describes "taxonomies" of various aspects of EsSP applications, based upon their decision context, perspective and assessment approach. It then examines, with a focus on European issues, a range of current and emerging regulatory and management applications to which the EsSP can be applied in light of this taxonomy.