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Policy instruments to ensure the provision of ecosystem services are often categories according to a trilogy that includes “sticks” (i.e. top-down policies, such as laws, regulations, restrictions, etc.), “carrots” (i.e. incentives) and “sermons” (i.e. best practices and guidance). Carrots, and in particular market-based instruments (MBIs) for the promotion and enhancement of ecosystem services have gained momentum in recent times. Among them, Payments for Ecosystem Services (PES) play a central role.

Different PES definitions have been proposed in the last ten to twelve years: an overview of these definitions is available (among others) in Derissen and Latacz-Lohmann (2013) and in Wunder (2015). A largely adopted definition is the one developed by Wunder (2005), according to which a PES is: