One little-noted thread running through many current issues – from the slaughters in the Middle East to the ethnic wars in Africa and Asia to the drought in the American west – is the growing irrelevance of national and state borders for either understanding modern problems or providing a framework for their solution. When European powers began conquering and settling the rest of the world, they divided it up according to their needs and rivalries, ignoring the realities they encountered. One of the most striking examples occurred in the states west of the Mississippi, where the national government imposed a two-dimensional grid on a three-dimensional landscape, without regard for the land’s physical features or native inhabitants.

Over 100 years ago, John Wesley Powell, who made the first recorded passage through the Grand Canyon despite having lost his arm at the Battle of Shiloh, argued that the only effective planning unit for western settlement was the watershed: "that area of land . . . within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community."

Two months ago, Thomas Friedman wrote of environmentalists’ vision for the eastern Mediterranean as a “region without borders because only by managing it as an integrated river system and water basin . . . can you sustainably manage its resources for the good of all. “

We can no longer afford to carve up the only world we have. We must learn now to share it.