When and how we might slip over the brink into catastrophe is impossible to foresee. But as the events of this summer suggest, we are already all too close to the edge of the kind of systemic failure experienced so many centuries ago by the Mayans, the ancient Puebloans, and the Viking Greenlanders. The only difference is that we may have no place else to go. Call it, if you want, Collapse 2.0.