Environmental progress doesn’t just happen. It’s been propelled by successive waves of innovation, each unleashing powerful new tools: Land conservation; Force of Law; Power of Market-Based Solutions. Today we are seeing the emergence of a Fourth Wave of environmental innovation. Some have used the phrase to call for a more actively engaged business sector that internalizes and assumes responsibility for environmental progress. Others have used it to describe the emergence of the environmental justice movement and an increasingly diverse and local activism powered by the grassroots. These are crucially important elements of the Fourth Wave, but in our view they do not tell the whole story, because they overlook dramatic changes in context — particularly the disruptive and accelerating changes triggered by the digital revolution. Regardless of one’s interpretation, the Fourth Wave is ultimately about innovation that gives people the power to take action.