Expertise in research integration and implementation is an essential but often overlooked component of tackling complex societal and environmental problems. We focus on expertise relevant to any complex problem, especially contributory expertise, divided into ‘knowing-that’ and ‘knowing-how.’ We also deal with interactional expertise and the fact that much expertise is tacit. We explore three questions. First, in examining ‘when is expertise in research integration and implementation required?,’ we review tasks essential (a) to developing more comprehensive understandings of complex problems, plus possible ways to address them, and (b) for supporting implementation of those understandings into government policy, community practice, business and social innovation, or other initiatives. Second, in considering ‘where can expertise in research integration and implementation currently be found?,’ we describe three realms: (a) specific approaches, including interdisciplinarity, transdisciplinarity, systems thinking and sustainability science; (b) case-based experience that is independent of these specific approaches; and (c) research examining elements of integration and implementation, specifically considering unknowns and fostering innovation. We highlight examples of expertise in each realm and demonstrate how fragmentation currently precludes clear identification of research integration and implementation expertise. Third, in exploring ‘what is required to strengthen expertise in research integration and implementation?,’ we propose building a knowledge bank. We delve into three key challenges: compiling existing expertise, indexing and organising the expertise to make it widely accessible, and understanding and overcoming the core reasons for the existing fragmentation. A growing knowledge bank of expertise in research integration and implementation on the one hand, and accumulating success in addressing complex societal and environmental problems on the other, will form a virtuous cycle so that each strengthens the other. Building a coalition of researchers and institutions will ensure this expertise and its application are valued and sustained.

Developing a new specialization - Integration and Implementation Sciences - may be an effective way to draw together and significantly strengthen the theory and methods necessary to tackle complex societal issues and problems. This paper presents an argument for such a specialization, beginning with a brief review of calls for new research approaches that combine disciplines and interact more closely with policy and practice. It posits that the core elements of Integration and Implementation Sciences already exist, but that the field is currently characterized by fragmentation and marginalization. The paper then outlines three sets of characteristics that will delineate Integration and Implementation Sciences. First is that the specialization will aim to find better ways to deal with the defining elements of many current societal issues and problems: namely complexity, uncertainty, change, and imperfection. Second is that there will be three theoretical and methodological pillars for doing this: 1) systems thinking and complexity science, 2) participatory methods, and 3) knowledge management, exchange, and implementation. Third, operationally, Integration and Implementation Sciences will be grounded in practical application, and generally involve large-scale collaboration. The paper concludes by examining where Integration and Implementation Sciences would sit in universities, and outlines a program for further development of the field. An appendix provides examples of Integration and Implementation Sciences in action