The intimate interdependence of human health and the ecosystems in which we are embedded is now a commonplace observation. For much of the history of public health, this was not so obvious. After over a century of focus on diseases, their biologic causes and the correction of exposures (clean water and air) and facilitation of responses (immunizations and nutrition), public health discourse shifted to embrace the concept of determinants of health as extending to social, economic and environmental realms. This moved the discourse and science of public health into an unprecedented level of complexity just as public concern about the environment heightened. To address multifactorial, dynamic impacts on health, a new paradigm was needed which would overcome the separation of humans and ecosystems. Ecosystem approaches to health arose in the 1990s from a rich background of intellectual ferment as Canada wrestled with diverse problems ranging from Great Lakes contamination to zoonotic diseases. Canada's International Development Research Centre (IDRC) played a lead role in supporting an international community of scientists and scholars who advanced ecosystem approaches to health. These collective efforts have enabled a shift to a research paradigm that embraces transdisciplinarity, social justice, gender equity, multi-stakeholder participation and sustainability.