Letter to the editor: Using classification systems to integrate ecosystem services with decision making tools

Mustajoki et al. https://doi.org/10.1016/j.ecoser.2019.101049 provided a valuable application of ecosystem services (ES) classification approaches to inform multi-criteria decision making analysis (MCDA) value trees. The exercise identified potential pitfalls of applying ES classification systems to MCDA and offered solutions by making adjustments to the value tree. The potential pitfalls included difficulty in narrowing down important ES, the lack of accounting for indirect benefits, and double counting. These pitfalls could also have been addressed, perhaps more efficiently, within the identification of ES before being placed into value trees. Broad use of this careful ES identification would improve their use in many decision making tools and applications.

ES classification approaches have developed from simple ES categories presented by the Millennium Ecosystem Assessment (MA) and The Economics of Ecosystems & Biodiversity (TEEB) to the present-day hierarchical classification systems of Common International Classification of Ecosystem Services (CICES) and the National Ecosystem Services Classification System Plus (NESCS). The MA brought classification science to the ES field by defining the supporting, regulating, provisioning, and cultural ES categories. The MA also warned that “These categories overlap extensively, and the purpose is not to establish a taxonomy but rather to ensure that the analysis addresses the entire range of services” (MA 2003, p. 38 in Finisdore et al. 2020). The MA authors were aware that classification systems must be complete, mutually exclusive, consistent, relevant to users’ needs, stable through time, comparable to other classification systems, flexible, and include a vocabulary and thesaurus (Finisdore et al., 2020).

TEEB recognized some of the overlap among the MA categories and the risks of double counting it engenders, noting that ES differ from economic benefits. CICES built on this observation by seeking to eliminate ecological processes as ES, while developing the first hierarchy of ES. The hierarchy was enabled by the final ecosystem services (FES) concept.

FES are the point where a product transitions from being predominately ecological to being predominately economic, and directly used or appreciated by humans (Boyd and Banzhaf, 2007). For example, consider that for fish to make it to market, a boat, fishing supplies, fuel, and labor are typically needed. The transition occurs with the application of manmade capital that allows the fish to be caught. The transition point is ultimately determined by who is using the product. To the fisher, fish available for harvest is the FES, whereas to a SCUBA diver, it is fish available for recreational viewing (Finisdore et al. 2020). FES allow CICES and NESCS to differentiate between ecological processes and economic benefits, and therefore reduce the chance of double counting.

Using CICES or NESCS Plus to identify FES includes the identification of users or user groups of the ecological end product provided by the ecosystem (e.g., fish for fishers). The process of identifying the user group and the ecological end product simultaneously helps narrow the list of important FES for an analysis. For example, only in a follow-up exercise to the one described in Mustajoki et al. were the lack of berry pickers (user group) in the target peatlands identified (Saarikoski et al., 2019). Moreover, there are benefits to identifying less important FES to any one study, as it can inform future studies.

Another advantage of careful ES identification is knowing which items are not FES. Peat extraction, for example, is not considered by most to be an ES because the regeneration time required to restore its ability to be used for recreation or berry picking is multigenerational. Mustajoki et al. recognizes this, but still identified peat extraction as an ES because of its importance to the study. Mustajoki et al. would likely have placed it into a separate branch of the MCDA value tree early on if peat extraction was identified consistently with the ES classification system. Similarly, CICES and NESCS Plus do not include indirect benefits in order to reduce double counting. A value tree, like the one described in Mustajoki et al., could have placed these indirect benefits in a separate branch from the start.

The ubiquitous use of the terms ‘provisioning,’ ‘regulating,’ ‘cultural’, and ‘supporting’ in the ES literature over the last two decades demonstrates how the MA categories unified thinking and language. As the field has developed, the flexibility and iterations of classification systems have been identified as ideal means for not only codifying existing ES knowledge, but also for incorporating new learning and spreading it across the ES field. Furthering the application of ES requires careful use of the term ‘ES classification systems’ and better engagement with their custodians to keep them updated and to address novel applications.