Jen Christiansen

Key Concepts

• Mining phosphorus for fertilizer is consuming the mineral faster than geologic cycles can replenish it. The U.S. may runout of its accessible domestic sources in a few decades, and few other countries have substantial reserves, which could also be depleted in about a century.
• Excess phosphorus in waterways helps to feed algal blooms, which starve fish of oxygen, creating “dead zones.”
• Reducing soil erosion and recycling phosphorus from farm and human waste could help make food production sustainable and prevent algal blooms.

As complex as the chemistry of life may be, the conditions for the vigorous growth of plants often boil down to three numbers, say, 19-12-5. Those are the percentages of nitrogen, phosphorus and potassium, prominently displayed on every package of fertilizer. In the 20th century the three nutrients enabled agriculture to increase its productivity and the world’s population to grow more than sixfold. But what is their source? We obtain nitrogen from the air, but we must mine phosphorus and potassium. The world has enough potassium to last several centuries. But phosphorus is a different story. Readily available global supplies may start running out by the end of this century. By then our population may have reached a peak that some say is beyond what the planet can sustainably feed.

Moreover, trouble may surface much sooner. As last year’s oil price swings have shown, markets can tighten long before a given resource is anywhere near its end. And reserves of phosphorus are even less evenly distributed than oil’s, raising additional supply concerns. The U.S. is the world’s second-largest producer of phosphorus (after China), at 19 percent of the total, but 65 percent of that amount comes from a single source: pit mines near Tampa, Fla., which may not last more than a few decades. Meanwhile nearly 40 percent of global reserves are controlled by a single country, Morocco, sometimes referred to as the “Saudi Arabia of phosphorus.” Although Morocco is a stable, friendly nation, the imbalance makes phosphorus a geostrategic ticking time bomb.

   
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