The Millennium Ecosystem Assessment (MA) has had a considerable influence on the work under multilateral environmental agreements dealing with biological diversity, including the Ramsar Convention on Wetlands. The MA developed a strong conceptual framework which brought together the natural and social sciences, and through that synergy promoted what it means to be sustainable. The MA provided a means to redefine the Ramsar Convention's wise use concept in terms of sustainability, especially the capacity of the ecosystem to continue to deliver the services on which other ecosystems and people depend. The messages from the MA impact also on the Ramsar Convention's concept of maintenance of ecological character; and thus the list of Wetlands of International Importance (Ramsar sites). ‘Change in ecological character’, which is a concept that is important in measuring Ramsar site effectiveness, can also be resolved in terms of ecosystem services – and thus the criterion for being and continuing to be a Wetland of International Importance essentially becomes an issue of capacity to deliver ecosystem services.