Innis Lecture: Environmental crises: past, present, and future

Environmental crises are distinguished by rapid and largely unexpected changes in environmental quality that are difficult if not impossible to reverse. Examples would be major extinctions and significant degradations of an ecosystem. I argue there are three preconditions for crisis: failures in governance, an ecological system exhibiting a tipping point, and an economy/environment interaction with positive feedbacks. I develop a simple model to illustrate how a crisis may arise, and draw on our knowledge of past and present crises to highlight the mechanisms involved. I then speculate as to whether climate change is indeed a crisis in the making.