This article reviews literature relating to the Great Barrier Reef (GBR) and aims to assess the current state of knowledge about (1) the “value” of ecosystem services (ES) provided by the GBR and (2) the way in which activities that are carried out in regions adjacent to the GBR affect those values. It finds that most GBR valuation studies have concentrated on a narrow range of ES (e.g., tourism and fishing) and that little is known about other ES or about the social, temporal, and spatial distribution of those services. Just as the reef provides ES to humans and to other ecosystems, so too does the reef receive a variety of ES from adjoining systems (e.g., mangroves). Yet, despite the evidence that the reef's ability to provide ES has been eroded because of recent changes to adjoining ecosystems, little is known about the value of the ES provided by adjoining systems or about the value of recent changes. These information gaps may lead to suboptimal allocations of resource use within multiple realms.