Florida’s Love-Hate Relationship With Phosphorus

The state has mined and abused the Devil’s Element for decades, and now it is increasingly fouling precious coastal waters

Blue-Green Algae
A father shows his son the awful-smelling algae hugging the shoreline of the St. Lucie River during a summer bloom in Stuart, Florida, in 2016. The algae fouled coastal waterways, created angry communities, closed beaches and had an economic impact as tourists and others were driven away by the smell and inability to enjoy the waterways. Joe Raedle / Getty Images

In the summer of 2018, in Stuart, a small beach community on the Atlantic Coast of Florida, some hundred panicked homeowners showed up at City Hall in the middle of the business day to demand something be done about the green goo plaguing their coastal waters. It was a sweltering July day, the kind towns like Stuart are built for, but signs on the boardwalk outside City Hall warned visitors:

Blue-​green algae—​Avoid contact with the water

As people at the meeting introduced themselves and stated their affiliations, it became clear this was not a typical gathering of environmentalists. They weren’t strategizing about how to protect some beleaguered species and the far​away lands or waters upon which it depends. These people, who represented businesses as well as homeowners’ associations and fishing and yachting clubs, spoke as though they were the threatened species.

“I need help,” said Will Embrey, a scraggly commercial fisherman whose business had collapsed right along with the region’s schools of mackerel not long after the green slime arrived. “There are a lot of people like me that need help.” The 45-​year-​old was suffering chronic stomach pain that was initially diagnosed as diverticulitis, and then ulcerative colitis, and then Crohn’s disease. Eventually doctors had given up trying to figure out what made Embrey so sick.

Embrey didn’t need to spend tens of thousands more dollars on more specialists, CT scans and lab tests to figure out the source of his illness. He knew it was the poisoned water, and he wasn’t alone.

So many patients had been showing up in local clinics and emergency rooms reporting mysterious respiratory issues and gastrointestinal illnesses that in the days before the City Hall meeting the head of the local health network had declared a public health “crisis.” To gauge the scope of the algae scourge that had become a summer fixture in Stuart over the previous few years, he instructed clinics to begin asking these patients whether they had been swimming or had other contact with open waters—​not good news for a place billed as one of Florida’s top ten beach towns.

“Un-​be-​lievable, ladies and gentlemen,” said the host of the meeting, a local Republican politician. “For anybody out there listening:​ This is real! This is happening!”

Stuart is not alone, and the problem is getting worse. In 2021, media outlets across the country reported some 400 U.S. bodies of water were infested with the green slime, a 25 percent jump over the previous year. Outbreaks plague beaches from Biloxi, Mississippi, to Lewiston, Maine, to Madison, Wisconsin, to Spokane, Washington. Between 2017 and 2019, more than 300 people across the United States ended up in emergency rooms after being exposed to toxic algae-​contaminated waters. One bloom on Lake Erie in 2014 contaminated the water supply for some 500,000 people in the Toledo, Ohio, area.

Blue-Green Algae Lake Erie
A boat kicks up a wake full of green algae a few hundred feet from Toledo’s water intake on Lake Erie in 2014. In August of that year, residents of the city were told not to drink or use their tap water due to the bloom. Ty Wright / For the Washington Post via Getty Images

Arguably the most important driver in the surging blue-​green algae blooms is one many people never think about. To begin to understand how this element in the toxic algae equation threatens waters worldwide, you need only to travel a little more than a hundred miles northwest of Stuart, Florida. There lies the essential root of Florida’s blue-​green algae problems, as well as similar water troubles across the continent—​even though nobody at the Stuart City Hall meeting back in 2018 seemed to have the slightest notion of how a relatively desolate sweep of central Florida, just a couple of hours’ drive to their northwest, could have anything to do with their public health crisis. The place is called Bone Valley.

About 35 miles east of Tampa is a quirky tourist attraction whose signature feature is a crane shovel big enough to scoop up several dump trucks’ worth of rocks and stones. Little kids play, sandbox-​style, in the tongue of pebbles spilling from its mouth. Bigger kids (and their parents) sift the pile for traces of long-​gone beasts.

Because the sandy finger of land that is present-​day Florida has for millions of years bobbed above and below the waterline as ocean levels have surged and shrunk, the center of the peninsula today is rich in fossilized remains from both land and sea. So rich that in the 1980s the little city of Mulberry converted a couple of old railroad cars into something of a fossil museum.

The museum is in the heart of Florida’s Bone Valley region that sprawls across more than a million acres in the west-​central part of the state. Here the fossilized remains of gargantuan armadillos lie buried among claws of extinct ground sloths that stood more than 12 feet tall. Remnants of elephant-​sized mastodons are in the mix, as are whales, sea turtles and megalodons—​a long-​gone species of jumbo shark with a mouth big enough to swallow a car.

The late 1800s discovery of this oddly matched cast of prehistoric characters frozen in time gripped the imagination of a public still coming to terms with the implications of Darwin’s theory of evolution.

“In this vast antediluvian sepulcher one may give free rein to the imagination, and in weird fancy resurrect the strange forms of animal life that walked the earth when this beautiful peninsula was but a straggling line of sand dunes and coral reefs,” reported one newspaper in 1890.

But central Florida’s troves of prehistoric remains, the author noted, weren’t just valuable as museum pieces. “To the practical man, the man with a purpose, the wealth seeker and the capitalist, these prodigious accumulations of [fossils] are Fortune’s offerings—​the opportunity of a lifetime.”

He even predicted the fossils would become more precious to Florida than gold was to California in the 1850s. The stony remains of so many long-​gone creatures (and, more importantly, so much of the sedimentary slabs of rock and pebbles entombing them) would actually prove to be far more valuable—​because you can’t sprinkle gold on a crop to grow food.

Florida’s fossil beds and their surrounding sedimentary rock could, it turned out, be pulverized and soaked in acid to create a staggeringly potent fertilizer that spurs agricultural crops to grow at incredible rates. Twenty-​seven of these fertilizer mines sprawl across nearly a half-​million acres of central Florida. Nine of the mines remain active today, and for every ton of crucial nutrients miners pull from the ground, another five tons of a mildly radioactive waste material is produced—​waste that is piled into mini mountains in Florida’s interior. These mounds of pollution are out of sight and mind for most Floridians—​except when their waste periodically seeps off site and threatens the state’s groundwater supplies as well as its coastal waters.

Waste Pile in Florida From Phosphorus Mining
A pile of the waste produced by the phosphate fertilizer industry. Waste from such sites can seep off site and threaten groundwater and coastal waters. Photographer via Wikimedia Commons

Yet the toxic piles of mine waste are allowed to keep growing because the fertilizer rock deposits at Bone Valley, along with a relatively small number of similar deposits scattered around the globe, are a big reason Earth’s food production has been able to double in the last half-century—​right along with its population.

These rocks are why today’s corn stalks, descendants of a wispy, grain-​rich type of grass that Native Americans first cultivated nearly 10,000 years ago, grow to apple-​tree heights and why bushel-​per-​acre yields have exploded almost fivefold since agriculture pioneers unleashed the powers of rock fertilizer on corn and other crops.

The Devil’s Element

Pulitzer Prize finalist Dan Egan investigates the past, present and future of phosphorus.

But there is a dark side to this chemical fertilizer’s miraculous ability to make things grow—​its potency doesn’t fade when it hits water. And much of today’s rock-​based fertilizer spread by farmers gets washed off croplands before it can be taken up by plant roots. So instead of making bumper crops of food, it tumbles into our streams, rivers and lakes, where it then fertilizes bumper crops of blue-​green algae.

Nobody pondered the downside of tinkering with nature in this fashion at the time the Bone Valley rock fertilizer deposits were discovered in the late 19th century.

Floridians were so dazzled by the jackpot under their boots—​about 75 percent of the rock fertilizer consumed in the United States today still comes from Florida—​that newspapers of the time wrote stories of men willing to shoot each other over roadbed pebbles that had been laid down before they were recognized as nutritional gold.

But what, precisely, makes these rocks so precious?


The element is precious and finite in the same way fossil fuels are. Yet we are blowing through Earth’s accessible deposits at such a pace that, just like oil production, some scientists now fear we could hit “peak phosphorus” in just a matter of decades, at which point we risk declining mining yields—​and chronic food scarcity.

“This is the gravest natural resource shortage you’ve never heard of,” an essay in Foreign Policy magazine proclaimed more than a decade ago.

The prospect of phosphorus shortages has only grown since, exacerbated by the wasteful way we are managing the dwindling reserves of a substance that is both a precious resource and a nasty pollutant. Globally, annual phosphorus rock harvests have roughly quadrupled since a half-century ago. Yet so much of the phosphorus we mine today and spread as fertilizer gets flushed off farm fields before it ever gets picked up by crops, let alone livestock, not to mention us. And much of that phosphorus that does make its way to the food on our dinner tables then makes its way, via sewer lines, into our waters instead of back onto croplands. Call it the phosphorus paradox—​at the same time as we are drawing down our increasingly precious caches of mineable phosphorus rock, we are overdosing our waters with it.

Some have predicted existing phosphorus reserves will play out by the end of the century, a time frame scoffed at by many who are knowledgeable about the issue, including those in the fertilizer business. But whatever the number of years, it is undeniable that we have cracked the circle of life and turned it into a straight line, and that line has an end, whether it’s in 100 years or 400 years. The trouble won’t come when the last of Earth’s phosphorus-​rich rock reserves have been mined, milled and spilled into our waters. It will come instead when phosphorus deposits play out in certain regions of the world, leaving relatively few countries—​even a few people—​largely in control of the fertilizer gusher that sustains 8 billion souls, and that day could be coming faster than you think.

Florida miners are on pace to run out of available rock in as little as 30 years, at which point the United States is at risk of becoming dependent on other countries to sustain its agriculture system.

For the last century, we’ve awakened to the power of mined phosphorus fertilizer and all the fruits it bears. But hitching our existence to mined phosphorus in this fashion carries its own Faustian burden. In exchange for breaking the natural throttle that limited how many humans Earth could sustain, we are polluting freshwaters with phosphorus fertilizer to the point those waters are increasingly prone to be too fouled to swim in, to fish upon and to drink from. We are soiling our own garden.

The only thing we can do now to protect and restore those waters, and at the same time ensure there is enough phosphorus—​enough food—​available for all the people yet to be born, is to train this latter-​day devil to chase its own tail, to restore the virtuous phosphorus circle of life that we’ve broken.

This will require a dramatic change in how much chemical fertilizer we use and how we use it. It’s also going to take a revolution in the way we manage civilization’s waste streams, human waste included.

The costs for not taming the Devil’s Element in this manner are already starting to mount.

Excerpted from The Devil’s Element: Phosphorus and a World Out of Balance by Dan Egan. Copyright (c) 2023 by Dan Egan. Used with permission of the publisher, W.W. Norton & Company, Inc. All rights reserved.

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