The notion of ecosystem services cuts across ecology and economy and calls for overcoming science’s fragmented and disciplinary nature (Norgaard, 2008). At the same time, clear and comprehensive definitions are required to avoid misunderstandings of the approach as a whole (Ghazoul, 2007a; 2007b; 2008a; 2008b; Allsopp et al. 2008; Klein et al. 2008; Kremen et al. 2008). The Millennium Ecosystem Assessment (MA) defines different kinds of ecosystem services and distinguishes among providing, regulating, supporting, and cultural servicing (MA, 2005). Although a valuable concept, it has been criticized for mixing processes (“means”) for achieving services with services themselves (“ends”) (Wallace, 2007; compare also Fisher & Turner, 2008).

In this essay we focus on another drawback, namely the challenge of adequately taking “sustainability” into account. As Norgaard (2008) remarks, neither the MA’s conceptual framework nor the empirical literature reviewed distinguishes ecological services provided by sustainable ecosystem flows from those generated through ecosystems slowly degrading over time, such as overused forests. We discuss here the ecosystem-service approach using pollination services as an example. We first distinguish between weak and strong sustainability, then consider efficiency requirements and their relationship to sustainability, and finally show the implications for policy recommendations as well as for the overall concept of ecosystem services.