A tiered assessment framework for interregional flows of ecosystem services from migratory species.

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services has called for assessments explicitly accounting for interregional flows of ecosystem services (ESs) across geographic scales. An important type of interregional ES flow is generated by the long-distance movements of migratory species. Many migratory species provide important benefits to people, and due to migration dynamics, ESs provided in one location may be affected by habitat conservation, or lack thereof, in other locations. The state of the science on interregional flows of ESs from migratory species, however, is nascent and lacks structure needed to consistently characterize flows. We developed a 4-tiered system for categorizing assessments and the conclusions they can support based on 4 levels of ecological and socioeconomic information, ranging from incomplete to high, and how they are combined. The 4 tiers of assessment are based on differing levels of detail in the estimation of system-level ecological and socioeconomic information on a species and the services it provides: telecoupled ESs, qualitative flows, quantitative static flows, and quantitative dynamic flows. Recent assessment studies largely fall within the first tier, which does not quantify flows. Socioeconomic and ecological information are needed to achieve each tier. Our framework can be used to identify and classify a range of methods, with varying time and data requirements, that can be used to maximize the information content and relevance of ES assessments for migratory species based on available resources.