The element phosphorus is absolutely essential to life. As David A. Vaccari notes, “it forms the backbone of DNA and of cellular membranes, and it is the crucial component in the molecule adenosine triphosphate, or ATP—the cell’s main form of energy storage.” Vaccari notes that the average human contains almost one and a half pounds, or about 650 grams, of the stuff. It’s mostly in our bones, as it is in every other vertebrate, in case you’ve ever wondered why bonemeal is both a fertilizer and a dietary supplement for livestock (yes, we’ve made them cannibals).
Phosphorus is also essential input for high-yield agriculture. Along with nitrogen and potassium, it’s one of the trinity of life-enriching elements that allow the world’s farmers to produce the food that feeds more than 8 billion of us—and that feeds something like 26 billion chickens, 1.5 billion head of cattle, and three-quarters of a billion pigs. Oh, and don’t forget all the corn grown for ethanol.
Agriculture literally mines nutrients from the soil, meaning that over time even the richest soils become depleted. So the human quest for fertilizer—substances to make the soil fertile—followed fast on the heels of agriculture itself. Humans have put wood ashes, manures, gypsum, fish, bloodmeal, horseshoe crabs, night soil—an evocative euphemism for human-produced manure—into the crop fields. We’ve mined islands of bird excrement to keep those crops coming. And we’ve even evidently mined battlefields for the bones of dead soldiers.
Today, nitrogen can be synthesized from the air, so it’s essentially limitless. Potassium, in the form of salts from dried-up sea beds, is quite abundant and expected to last for centuries. Phosphorus, however, is rather more limited. Nothing can substitute for it, and we’re using it much faster than it’s naturally produced—a process that takes many millions of years. With the number of people following meat- and dairy-based diets—which consume more phosphorus than plant-based diets—expected to double by 2050, there are ever-dire predictions of phosphorus becoming a lot more expensive or even running out.
Some have argued that we’re approaching peak phosphorus, like peak oil but perhaps even more vital to humanity.
Phosphorus comes from mined rock. Four countries—Morocco, China, the US, and South Africa—control 83 percent of the world’s reserves and two-thirds of current production. Morocco tops the list for reserves, because its share includes the resources of Western Sahara, a former Spanish colony that’s now what the UN terms a “non-self-governing territory.” This status is contested between the Moroccans and the indigenous Sahrawi. The US’s major source, in Florida, is expected to run out in a few decades.
But there’s another problem with phosphorus besides the fact that we’re using it at a much higher rate than it can be replenished and its unequal distribution around the world. The stuff makes everything grow. So when it enters the water through runoff from farm fields or overflow from the oceans of animal waste created by factory meat production, it supercharges algal blooms. In dying, these algae suck so much oxygen out of the water nothing else can live in that water, resulting in the hypoxic “dead zones” now found in the world’s fresh and salt waters. Shrimpers in the Gulf of Mexico, for instance, are thus direly connected to farmers in the Midwest.
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And when it comes to cyanobacteria, also known as blue-green algae, the end result of one of these blooms can be deadly masses of cytotoxins. In recent years, these have been threatening drinking water supplies and closing beaches and fishing industries from the Finger Lakes to the Great Lakes to Florida. Even breathing the toxic air these blooms produce can be harmful.
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Christopher J. Rhodes argues that greater efficiencies in phosphorus usage are vital, especially considering that a lot of what’s currently applied to farms is simply washed or leached off in the rain. Recycling comes into play as well: there’s plenty of phosphorus in animal excretion, which is why manure have been a go-to fertilizer for at least eight thousand years.
Twenty-first-century Americans may prefer not to think about the history of using human excrement and urine as manures. But such practices were once as common here as they still are in other parts of the world today. Take Brooklyn and Queens, home to some of the most productive farmland counties in the US in the second half of the nineteenth century. They worked on a simple formula: farmers sent their produce to Manhattan, and Manhattanites, in turn, sent their faeces to the farms.
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