Addressing complex transnational problems requires coordination from different professionals. The emergence of new actors and issues has been addressed by those interested in studies of organizations through concepts and methods that highlight the importance of communities, fields, and networks. These approaches are important in identifying the sources of what becomes established, but less geared to identifying interactions that are emergent. This article extends a linked ecologies approach to emergence, arguing that interaction on transnational issues should first be understood by how they are conceptually linked by actors and organizations. A linked ecologies approach asks us to displace locating known actors within structures and instead pays attention to professional interactions on how ‘issue distinctions’ are made, the relationship between issue distinctions and professional tasks, and who and what are included and excluded. A linked ecologies approach provides a fruitful way of identifying actors and distinctions on issues that are emergent. These conceptual and methodological points are demonstrated through a study of how medical experts, demographers, and economists forge issue distinctions in relation to low fertility in advanced industrialized countries.