Is the focus on “ecosystems” a liability in the research on nature’s services?

For the last 20 years, the concept of ecosystem has constituted one of the key pillars on which the study of “ecosystem services,” i.e., the benefits that human populations derive from nature, has been based. Yet, at this stage, one could argue that, in general and especially in fields related to agriculture, the ecosystem framework tends to limit unnecessarily the range of benefits to humans that are considered in practice, to hinder the necessary measurement of services, and to make it challenging to convince individuals to take nature's services into account in their decision making. In the present Perspective piece, we analyze these 3 arguments in detail, conclude that the current focus on ecosystems is more a liability than an asset in the field, and suggest a return to the less constraining notions of “nature's functions and services,” without a necessary tie to ecosystems.The services provided by nature to human populations have been the object of extensive research since WWII (e.g., Baveye et al., 2013). In the hundreds of articles, books, and reports published on the topic in the 1960s and 70s, terms like “environmental services,” “environmental amenities,” or “nature's services” (Westman, 1977; Baveye et al., 2013) were generally used to refer to benefits derived from nature. Westman (1977), an ecologist by training, perceived nature through the lens of a broadly-defined concept of “ecosystem,” but did not see the need to invoke this concept when referring to the benefits humans derive from nature. The alternative expression of “ecosystem services,” apparently coined by Ehrllich and Ehrlich (1981), gained little traction until 1997, but was then given significant prominence by Costanza et al. (1997), Daily (1997), and especially the publication of the Millenium Ecosystem Assessment (2005). This terminology became the norm in the field, at least until recently. In the last couple of years, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) proposed what they viewed as a paradigm shift away from the concept of “ecosystem services” toward that of “nature's contributions to people” (NCP), perceived as significantly better in a number of respects (Díaz et al., 2015; Pascual et al., 2017). Nature's contributions to people are defined as “all the contributions, both positive and negative, of living nature (diversity of organisms, ecosystems, and their associated ecological and evolutionary processes) to people's quality of life” (Díaz et al., 2018). This proposal has rapidly stimulated an occasionally heated debate in which various protagonists (e.g., Braat, 2018; Faith, 2018; Peterson et al., 2018; see also the many e-letters posted at http://science.sciencemag.org/content/359/6373/270/tab-e-letters) have tried to demonstrate the respective merits of the “ecosystem services” and NCP perspectives. One could argue at this stage that these relative merits, let alone the fundamental differences among the two terminologies, remain very fuzzy. At first glance, one would be tempted to say that a major difference is that the NCP terminology has eliminated any reliance on the notion of ecosystem, which would constitute a clear paradigm shift, but closer scrutiny shows that this is not the case; ecosystems still constitute implicitly the framework in which NCP are envisaged.Yet, as we advocate in this short article, dropping the concept of ecosystem when assessing the functions or services of nature, at least in certain circumstances, might be a step in the right direction. Especially in an agricultural context, a number of obstacles are associated with the concept, and constitute as many compelling arguments, if not necessarily to adopt the controversial notion of Nature's Contributions to People, at least to move away from that of “ecosystem” services.Criticisms of the concept of ecosystem among ecologists are not new. They have surfaced periodically over the last 30 years (e.g., Golley, 1991; Blew, 1996; Gignoux et al., 2012; Tassin, 2012; Silvertown, 2015). Several authors have criticized in particular the dichotomy between humans and nature that the notion of ecosystem implies (e.g., Berkes and Folke, 1998), and the hierarchical, scale-dependent structure of many ecosystems, which raises tricky methodological issues (Miller, 2008; Scholes, 2017). Various researchers have argued that, in its classical acception, the concept of ecosystem cannot be reconciled with the common observation of ecological systems as metastable adaptive systems that usually operate far from equilibrium (e.g., Blandin and Bergandi, 2000; O' Neill, 2001), and new conceptualizations of ecosystems have emerged (e.g., Jørgensen et al., 2007).Yet, the reasons for moving away from the classical concept of ecosystem when dealing with nature's services are different than those traditionally advocated by ecologists. There are basically three key reasons, namely that the ecosystem framework tends to limit unnecessarily the range of benefits to humans that are considered in practice, that it causes as yet unresolved difficulties for the measurement of ecosystem services, and that it makes it challenging to convince stakeholders to take nature's services into account in their decision making.