Work in environmental ethics, and on environmental values more generally, is rife with references to the concept of ecosystem function. In much of this work, the concept of ecosystem function is being asked to shoulder a heavy normative burden. Ecosystem holists of various stripes, from Aldo Leopold to Holmes Rolston, use ecosystem function support the moral standing of ecosystems. Here functional integrity plays the role that interests play in a more individualistic ethics – it allows us to determine the specific nature of our duties to ecosystems. Less radically, conservation biologists seek to underwrite the value of biodiversity by tying it to ecosystem function, thereby capturing, at last, ecology's Holy Grail of connecting diversity and stability. Ecological economists see ecosystem function as key to maintaining the sustainable delivery of valued ecosystem goods and services. The centrality of ecosystem function to ecological inquiry generally already points up the need for an explication of the concept; these normative demands render that need even more urgent. Yet problems with the individuation of ecosystems and the absence of ecosystem-level selection raise questions about whether a successful explication will be forthcoming. The goals of this paper are twofold: first, to clarify the various ways in which the concept of ecosystem function is being asked to do this normative heavy lifting and, second, to raise questions about the extent to which the conceptual foundations of the notion are secure enough to justify confidence that it will be up to the task.