Societal adaptation to climate change requires measures that simultaneously reduce poverty, protect or restore biodiversity and ecosystem services, and remove atmospheric greenhouse gases. Ecosystem-based adaptation to climate change is the type of adaptation that aims to combine these outcomes and is particularly relevant to developing nations that safeguard most of the planetary biodiversity and healthy ecosystems. Although conceptually new, ecosystem-based adaptation is fastly gaining traction both as a research arena and as an integrated policy instrument. This paper aims to revisit this concept and to discuss the science and policy challenges faced by it. It argues that ecosystem-based adaptation is a policy mix that promotes adaptive transition, which is a step towards sustainability transitions. It faces two major challenges in promoting transitions towards adaptation and sustainability. First, research on ecosystem-based adaptation mostly takes place within the socio-ecological systems framework, which is often carried out in isolation from socio-technical systems research. It is widely recognized that both types of research should be integrated, for the benefit of science and policy-making, and the paper discusses the potential of ecosystem-based adaptation in providing such bridge. Second, there is a divide between global and local research and policy, while at local level this divide is related to the setting (e.g., coastal, urban, rural). The resulting mosaic of information lacks integration, which hinders scalability of actions and policies. Finally, I examine the opportunity for ecological and conservation scientists to interact with social, economic and political scientists on ecosystem-based adaptation research, and discuss how timely this opportunity is for Brazil.