"World food production depends on phosphorus. Are we about to run out?"

No.
We've been down this road a half dozen times, most notably when Vaclav Smil took on Jeremy Grantham. See after the jump.

From ScienceNorway, June 30:
For the past decade, scientists have warned that phosphorus reserves are running low. Are we heading towards a crisis?

The plants and cultivation methods used by modern agriculture are entirely dependent on fertilizers, where two of the most important components are nitrogen and phosphorus. Nitrogen fertilizers can be produced in factories and are in practice a renewable resource.

But the same is not true of the phosphorus in fertilizers.

Currently, phosphorus is mined from rocks that contain the substance — called rock phosphate — that are mined in a few places around the world, especially in China and the Moroccan-occupied territory of Western Sahara.

And these resources cannot last forever.

Some predict just decades left

In 2008, some calculations predicted that the world would begin to experience scarcities of rock phosphorus as early as 2030. The consequence would first be dramatically increased fertilizer prices, and gradually declining crops.

In recent years, scientists have regularly sounded warnings of a looming crisis. In 2019, for example, the British newspaper The Guardian wrote that we only have a few decades of consumption left.

But the information on the topic can be confusing.

Others say 2000 years

Representatives from fertilizer producers themselves do not foresee any crisis.

“We have enough phosphorus for at least 2000 years at today's levels of consumption,” wrote Anders Rognlien from Yara, a fertilizer manufacturer, in an opinion piece in the Norwegian national newspaper Aftenposten in 2010.

Some researchers agree.

For example Pedro Sanchez, a researcher at Columbia University in New York, was quoted in a 2013 blog post as saying, “In my long 50-year career, once every decade, people say we are going to run out of phosphorus. Each time this is disproven. All the most reliable estimates show that we have enough phosphate rock resources to last between 300 and 400 more years.”

So is there a crisis or not?

Eva Brod, a researcher at the Norwegian Institute of Bioeconomy Research (NIBIO) studies phosphorus in agriculture. So does Professor Petter Jenssen at the Norwegian University of Life Sciences (NMBU).

They both conclude that we’re not about to immediately run out of phosphorus.

Nevertheless, they agree we need to do something about it.

More than 250 years

“The latest overview of the world’s phosphate reserves was conducted by Håkan Jönsson at the Swedish University of Agricultural Sciences", says NMBU’s Jenssen.

“His assessment shows that we have more than 250 years at current levels of consumption.”

But these kinds of estimates are often uncertain. They give an indication of the size of the deposits where rock phosphate is currently being mined, and the projections are based on how much phosphorus can be extracted using current technology and at a reasonable cost.

However, that doesn’t mean these are the only sources of rock phosphate. There may be many reserves elsewhere on the globe that are not being mined because they are more inaccessible, are less concentrated or are of lower quality.

Toxic and radioactive

“For example, a lot of rock phosphate is contaminated with cadmium or uranium,” says Brod from NIBIO.

If phosphorus from these kinds of sources is to be used in fertilizers, it must first be treated so that the soil is not contaminated with heavy metals or radioactive substances. It’s too costly right now for this kind of decontamination to be worthwhile.

But if the best rock phosphate begins to run out — and technology evolves — lower quality sources may suddenly become of interest nonetheless....

....MUCH MORE

And December 10, 2012:
Vaclav Smil Takes on Jeremy Grantham Over Peak Fertilizer
We posted the whole of Mr. Grantham's Nov. 15 Nature piece for fear it would go behind Nature's paywall.
To date it hasn't. Also to date I haven't come through on my assurance in Nov. 24ths "Jeremy Grantham "On the Road to Zero Growth" as His Co-head of Asset Allocation Does the Full Monty". I promise I'll get to it.

We have almost as many posts on Professor Smil as we do on Mr. Grantham. This is the first time they've been together. I feel very uncomfortable being on the opposite side of Mr. G on just about anything but in this case Smil is right.

From The American:
Jeremy Grantham, Starving for Facts

 A column by legendary asset manager Jeremy Grantham is more suitable for the tabloids than for one of the world’s oldest and most prestigious scientific weekly magazines.

Jeremy Grantham, a well-known presence in the financial world, recently published a World View column in the journal Nature in which he concludes that, “simply, we are running out’’ of almost all commodities whose consumption sustains modern civilization. There is nothing new about such claims, and since the emergence of a vocal global peak oil movement during the late 1990s, many other minerals have been added to the endangered list. Indeed, there is now a book called Peak Everything. What makes Grantham’s column – published under the alarmist headline “Be Persuasive. Be Brave. Be Arrested (If Necessary)” – worth noticing, and deconstructing, is that he puts his claims in terms more suitable for tabloids than for one of the world’s oldest and most prestigious scientific weekly magazines.

His direst example is “the impending shortage of two fertilizers: phosphorus (phosphate) and potassium (potash). These two elements cannot be made, cannot be substituted, are necessary to grow all life forms, and are mined and depleted. It’s a scary set of statements…. What happens when these fertilizers run out is a question I can’t get satisfactorily answered and, believe me, I have tried.’’ Well, he could have tried just a bit harder: an Internet search would have led him, in mere seconds, to “World Phosphate Rock Reserves and Resources,” a study published in 2010 by the International Fertilizer Development Center (IFDC) and funded by the U.S. Agency for International Development.

This detailed assessment of the world’s phosphate reserves (that are the part of a wider category of resources that is recoverable with existing techniques and at acceptable cost) concluded that they are adequate to produce fertilizer for the next 300 to 400 years. As with all mineral resource appraisals (be they of crude oil or rare earths), the study’s conclusions can be criticized and questioned, and the statement by the Global Phosphorus Research Initiative is perhaps the best document of that kind. But even the most conservative interpretation of IFDC’s assessment shows that phosphates have a reserve/production ratio well in excess of 100 years, higher than that of many other critical mineral resources.

Grantham could have also checked the standard, and the most often quoted, sourcebooks on the world’s mineral resources, Mineral Commodity Summaries, published annually by the U.S. Geological Survey (USGS). In the latest edition, he would have found that the USGS made significant revisions to its phosphate rock reserves data for Morocco, Russia, Algeria, Senegal, and Syria, and that it now puts the global reserve/production ratio at about 370 years....MORE

If interested see also:
"Jeremy Grantham on Tesla, Fertilizer Wars" (and lessons learned from 47 years at the market)
The Allure of Guano
Questions America Is Asking: "Are We Entering a New Golden Age of Guano?"
New York Guano

 More than you ever wanted to know. First a partial re-post:
Equity Valuation and Forecasting Future Returns and a Gift for our Readers
A subject near and dear to my heart. I may be the only person I've ever met who read every page of The Cowles Commission's Common Stock Indexes 1871-1937.
[you must be a blast at parties -ed]
(links below)...

And many more.