Methods for mapping ecosystem service supply: a review

Mapping key areas for ecosystem service (ES) supply is essential for the development of strategies that will ensure their future supply. Given the rapid development in this area of research, we performed a review of different approaches used to map ES, with a special focus on those that use social–ecological data. We used an analytical framework based on five criteria for analyzing and comparing the methodological approaches: the types of ES, availability of data sources, types of data sources, spatial scale, and methods used to model ES. We found that regulating services were the most commonly mapped, followed by provisioning, cultural, and supporting services. Secondary (readily available) data were used more frequently than primary data to map ES. Biophysical data (land-cover variables) and mixed sources (databases like global statistics) were the most commonly employed ones. Most studies were performed at the regional or at the national scale. The most commonly used method to model services was the development of models based on the well-known causal relationships between environmental variables, followed by the extrapolation of ES values from primary data to the total analyzed area frequently using land-cover maps. Our synthesis reveals that the majority of studies are based on secondary data, applied at broad scales, without validation techniques. There is an urgent need to develop methods for deepening our understanding of the social–ecological processes behind the supply of ES in order to improve our ability to map ES for decision making.