All life needs phosphorus and agricultural yields are improved when phosphorus is added to growing plants and the diet of livestock. Consequently, it is used globally as a fertilizer – and plays an important role in meeting the world’s food requirements.
In order for us to add it, however, we first need to extract it from a concentrated form – and the supply comes almost exclusively from phosphate mines in Morocco (with far smaller quantities coming from China, the US, Jordan and South Africa). Within Morocco, most of the mines are in Western Sahara, a former Spanish colony which was annexed by Morocco in 1975.
The fact that more than 70 percent of the global supply comes from this single location is problematic, especially as scientists are warning that we are approaching “peak phosphorus”, the point at which demand begins to outstrip supply and intensive agriculture cannot continue to provide current yields. In the worst case scenario, mineable reserves could be exhausted within as little as 35 years.
So what is going on – and how worried should be?
In nature, phosphorus only exists bound to oxygen, which is called phosphate. It is in this form that it is mined. Chemists can remove the oxygens bound to it to get elemental white phosphorus, which glows in the dark, but it is so unstable that it spontaneously ignites on exposure to air.
Phosphate easily diffuses through soil or water and can be taken up by cells. When phosphate meets free calcium or iron, they combine to give highly insoluble salts.
In the first half of the 19th century, Justus von Liebig popularized the law of the minimum for agriculture, which states that growth is limited by the least available resource. It was soon discovered that this was often some form of phosphorus.
As a consequence, bones – comprised mostly of calcium and phosphate – from old battlefields were dug up to use in farming. Guano, large accumulations of bird droppings, also contains high concentrations of phosphorus and was used to fertilize crops. But supplies of this were soon depleted. As demand increased, supplies had to be mined instead.
But this applied inorganic phosphate fertilizer is highly mobile and leaches into watercourses. In addition, phosphate rock weathers and is also ultimately washed into the ocean where it either deposits as calcium phosphate or is taken up by marine organisms who also eventually deposit on the ocean floor when they die. Consequently, terrestrial phosphorus doesn’t really disappear, but it can move beyond our reach.
To complicate matters further, even the phosphorus we can use is largely wasted. Of the phosphorus mined as fertilizer, only a fifth reaches the food we eat. Some leaches away and some is bound to calcium and iron in the soil. Some plant roots have the ability to extract the latter, but not in large enough quantities to retrieve all of it.
In addition to these inorganic forms, phosphate is also converted into cellular compounds, creating organically-bound phosphorus, such as phospholipids or phytate. After the death of an organism, these organic phosphorus compounds need to be returned into the useable phosphate form. How much organically-bound phosphorus is present in soils depends on the number and activity of the organisms that can do this.
Agricultural soils are usually rich in inorganic phosphorus while in undisturbed ecosystems, such as forests and long-term pastures, organically-bound phosphorus dominates. But agricultural land is often depleted of phosphorus during harvest and land management practices such as ploughing, hence the addition of phosphate-containing fertilizers.
Spreading manure and avoiding tillage are ways of increasing microbial abundance in the soil – and so keeping more phosphorus in an organically-bound form.
The risks of peak phosphorus can be countered with some simple solutions. Eating less meat is a start as huge amounts are used to rear livestock for meat. The chances are that agricultural yields are limited by phosphorus availability and will be further stretched as the global population grows.
Humans are themselves wasteful of phosphorus, as most of what we take in goes straight out again. Fortunately, technologies have been developed to mine phosphorus from sewage, but at present are too expensive to be practical.
Peak phosphorus does not mean that phosphorus will disappear, rather that the reserves with mineable high concentrations are depleting. Instead, we are increasing the background concentrations of phosphorus and adding it to the ocean floor. More sustainable phosphorus use requires a greater appreciation and understanding of the many organisms that make up soils – and the part they play in phosphorus distribution – or we may no longer be able to feed the world at an affordable price.
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Popularly known as “cavemen,” Neanderthals were ancestral humans who lived in Western Europe, on the eastern shores of the Mediterranean, and in southwestern and central Asia from about 400,000 to 40,000 years ago. They lived in glacial environments during the Ice Age as well as in warmer time periods. Their foreheads were low and receding in contrast to the high, almost vertical foreheads of modern humans. They also had protruding faces and heavy brow ridges above their eyes. While it’s an open question whether you’d recognize a Neanderthal if you saw one on the street, groomed and dressed in modern clothes, I like to think they’d blend in at my museum’s holiday party. Read More
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Throughout the Vietnam War, they flew 2,602 missions, releasing silver iodide, a compound that seeded clouds and exacerbated monsoons—or so the thinking went. Dubbed “Operation Popeye”, this rainy warfare would last from 1966-72, until banned under the 1977 Enmod Treaty on weather warfare. Popeye wasn’t the only attempt to weaponize seasonal events, but it was the most infamous. There was also, for example, an “exercise” aiming to make the Hồ Chí Minh trail muddier, named “Commando Lava”. The problem with infamy, however, is that the subjects of it rarely live up to the legend. Read More
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That’s Thomas G. Kaye’s philosophy: if you can fossilize it, you can fire a laser at it. Kaye, of the Foundation of Scientific Advancement, Sierra Vista, developed a laser-scanning technique that reveals stunning new details buried within dinosaur fossils — so meta. Now he’s traveling the world placing new specimens in his crosshairs.
Kaye is joined by Mike Pittman, who’s already infamous at Discover for spotting fossils while taking a whiz in the Gobi Desert. Together, they’re trekking around the world armed with nothing more than their portable laser and an inquisitive eye. Read More
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The study by researchers at the University of Edinburgh and EPFL in Switzerland found red squirrels from England, Scotland and Ireland were infected with leprosy. In particular, a group from Brownsea Island on the south coast of England had a strain of the disease virtually identical to one that infected humans in the middle ages. Read More
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His proclamation comes with a significant caveat that will pop the bubbles in your champagne. Austin is so interested in these studies because they all happened in mice, in a lab. When the hundreds of different drugs that made mouse tumors disappear were carried forward to human trials, they went in and came out without doing what they promised. Or worse, they turned out to be toxic. Read More
Back in August, it seemed that Sir Arthur Conan Doyle, the creator of Sherlock Holmes, was cleared of playing any role in one of the greatest hoaxes in scientific history. But in true Sherlockian form, there may still be a twist in this case that appears to be closed. And it’s a fitting discussion on Halloween.
The infamous ‘Piltdown Man’ hoax culminated in 1912 after esteemed geologist Sir Arthur Smith Woodward and amateur archaeologist Charles Dawson announced they had discovered the ‘missing link’ between ape and man. It featured a human-sized skull with an ape-like jaw, and it fooled scientists for 40 years before it was debunked.
So how did Conan Doyle get involved in this, and why should he still remain on the suspect list, despite the latest evidence? Stay with me as I dig deeper into this longstanding controversy. Read More
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The familiar bright yellow Cavendish banana is ubiquitous in supermarkets and fruit bowls, but it is in imminent danger. The vast worldwide monoculture of genetically identical plants leaves the Cavendish intensely vulnerable to disease outbreaks. Fungal diseases severely devastated the banana industry once in history and it could soon happen again if we do not resolve the cause of these problems. Plant scientists, including us, are working out the genetics of wild banana varieties and banana pathogens as we try to prevent a Cavendish crash. Read More