Forty years ago, The Limits to Growth study addressed the grand question of how humans would adapt to the physical limitations of planet Earth. It predicted that during the first half of the 21st century the ongoing growth in the human ecological footprint would stop-either through catastrophic "overshoot and collapse"-or through well-managed "peak and decline." So, where are we now? And what does our future look like?  In the book 2052, Jorgen Randers, one of the coauthors