Phosphorus

Globally, phosphorus is available in extremely limited quantities. Next to clean water, writes Bill Mollison, phosphorus will be one of the inexorable limits to human occupancy on this planet. It exists in sedimentary rock.

I didn’t put rocks in the same category as animals: I didn’t mind using them. The problem was getting them. They had to be quarried—mined—then ground up, and transported. Without vast amounts of fossil fuels, would that even be possible? And what about when we’d used it all up? I was back to the same shelf at the feed store. I could buy rock phosphate, decide that because it was organic I was doing the good, green thing and simply not think about it anymore. But wasn’t there a sustainable source I could get on my own? I asked the question, but hated the answer.

Bone meal from land animals is a traditional source, and most farms (up to 1940) kept a flock of pigeons as their source. Or I could theoretically get it from seabirds and salmon [who] do try to recycle it back to us but we tend to reduce their numbers by denying them breeding grounds. I was ninety miles from the ocean. I was barely a mile from the Connecticut River, one of the southernmost habitats for Atlantic salmon, but there haven’t been anadramous fish in the Connecticut since the river was dammed almost two hundred years ago, to power the mills.

(From The Vegetarian Myth)