We should worry about peak phosphorus, yes. It is going to become a major issue with very dire consequences. Yet it's all a bit ridiculous because before the Green Revolution--before the advent of industrial agriculture--we got along just fine without rock phosphate (the form of phosphorus experts are referring to when they talk about "peak phosphorus").
We're not about to run out of phosphorus. We're about to run out of the form of phosphorus that allows industrial agriculture and monocropping to exist. Ultimately, this is a great thing. Industrial agriculture is unsustainable and this one hard limit will certainly be its downfall if nothing else is able to bring it down. Unfortunately, billions of bellies around the globe depend on this unsustainable system of agriculture, and hunger and starvation are all but inevitable as phosphate reserves are depleted. And long before reserves are depleted, the price of rock phosphate will skyrocket, and along with it the price of food. The crisis is coming soon. World production is expected to peak around 2034, and while that might make it seem like we have plenty of time, we don't. There are a number of issues, the main one being the fact that 90% of remaining reserves are located in only five countries, and the bulk of that 90% resides in just two of those countries (China and Morocco). The US is one of the top five producers, but we have already passed our peak and we are now consuming more than we produce and must import some of our rock phosphate each year. As reserves decline, those countries with large reserves will begin to limit exports, creating global shortages. An additional issue, already at play, is that the best phosphate has already been mined. What's left is more expensive to extract and contaminated with heavy metals and other toxins.
The answer to peak phosphorus is to go back to the old ways, the sustainable ways. Phosphorus is abundant in nature and can be recycled many times before it ultimately gets washed out to sea. Animal manure, urine, humanure, bones, bodies, leaves, food waste--all of these things are rich in phosphorus. One Swedish study found that the urine output of one person is rich enough in nutrients to produce 50-100% of a person's food supply--just one person's urine! Phosphorus depletion should be a non-issue. It's so easily remedied. But at this point, how do we transition back to sustainable agriculture, so that billions of bellies don't go hungry? That's the challenge.
We can all do what we can locally--in our backyards and by supporting farms that cycle their own nutrients instead of importing them. But we also need to support global efforts aimed at sustainable agriculture. Although all of us will be hit by high prices, those of us in the western world who aren't so dependent on the products of industrial agriculture will probably weather the transition just fine. It's everyone else we need to worry about, especially the world's urban poor.