"If you wanted to really mess with the world’s food production, a good place to start would be Bou Craa, located in the desert miles from anywhere in the Western Sahara. They don’t grow much here, but Bou Craa is a mine containing one of the world’s largest reserves of phosphate rock. Most of us, most days, will eat some food grown on fields fertilized by phosphate rock from this mine. And there is no substitute.
The Western Sahara is an occupied territory. In 1976, when Spanish colonialists left, its neighbor Morocco invaded, and has held it ever since. Most observers believe the vast phosphate deposits were the major reason that Morocco took an interest. Whatever the truth, the Polisario Front, a rebel movement the UN recognizes as the rightful representatives of the territory, would like it back.
Not many people would call phosphate a critical issue or one with serious environmental consequences. But even leaving aside the resource politics of the Sahara, it is an absolutely vital resource for feeding the world. It is also a resource that could start running low within a couple of decades — and one we grossly misuse, pouring it across the planet and recycling virtually none of it."