Sitting in a Panera in Boston's financial district in early July with Jeremy Grantham, I suddenly found myself considering how I might safeguard my children's and notional grandchildren's future by somehow engineering the U.S. annexation of Morocco. Grantham, the founder and chief strategist of the asset-management firm GMO, was reading aloud from a rough draft of his next quarterly letter to investors, in which he ranks some long-term crises of resource limitation along a scale from "merely serious" to "dangerous."