Article history: Received 10 May 2007 Received in revised form 20 September 2008 Accepted 23 September 2008 Available online 28 October 2008 The concept of ecosystems services has become an important model for linking the functioning of ecosystems to human welfare. Understanding this link is critical for a widerange of decision-making contexts.While there have been several attempts to come upwith a classification scheme for ecosystem services, there has not been an agreed upon, meaningful and consistent definition for ecosystem services. In this paper we offer a definition of ecosystem services that is likely to be operational for ecosystem service research and several classification schemes.We argue that any attempt at classifying ecosystem services should be basedonboth the characteristics of the ecosystemsof interest andadecision context forwhich the concept of ecosystem services is being mobilized. Because of this there is not one classification scheme that will be adequate for themany contexts in which ecosystem service researchmay be utilized.We discuss several examples of how classification schemeswill be a function of both ecosystem and ecosystem service characteristics and the decision-making context. © 2008 Elsevier B.V. All rights reserved.