Conceptual innovations are a central feature of global environmental governance. Confronting degradation and unsustainability, scholars and practitioners turn to new concepts to identify, make sense of, and chart new directions towards meaningful governance solutions. But why do some concepts create lasting changes to governance institutions and governance practices, while others do not? Ideational theories of international relations highlight the importance of normative fit. In this paper we analysis the concept of ecosystem services to show that normative fit is just one dimension of governance fitness, which also includes practical fitness. Ecologists and economists coined the concept of ecosystem services to make biodiversity conservation intelligible to decision-makers versed in economic thinking. It has gained rhetorical traction, but ultimately failed to change how we treat nature because it lacks practical fitness. We interviewed fifty-six individuals working in twelve international organizations that have sought to translate the concept of ecosystem services into practice. Our analysis reveals forces limiting practical fit and constraining institutional uptake at three levels of analysis: structural, organizational, and agent. We present a cautionary tale that pushes scholars to carefully consider practical fit alongside normative fit when suggesting new concepts as organizing frames for how we govern global environmental challenges.