The discipline of geography encompasses both natural and social sciences and has the natural advantage of enabling the study of sustainability from a transdisciplinary perspective. There are great opportunities for geographers to participate in sustainability research. However, while geographers have set sustainability goals, they have rarely clarified the details for reaching those goals. Current knowledge on the relationship between humans and the environment and the methodologies for studying this relationship are inadequate to solve the transdisciplinary questions in sustainability science. Five research areas: geographical processes; ecosystem services and human wellbeing; human-environmental systems; sustainable development; and geo-data and modelling for sustainability are proposed as those needed to help geography achieve sustainability. The key objective of promoting geography for sustainability is to reveal the mechanisms of human-environmental system dynamics. This depends on understanding the processes in the natural and social systems and their mutual feedback as well as clarifying the relationships between the structures, functional characteristics and interactions in the human-environmental systems at multiple scales. The advancement of geography and its methodologies and technologies will provide a more profound understanding of the future. Geographers have the responsibility of promoting the discipline as the key pathway for carrying natural and social sciences towards sustainability.