The scientists were pointing to “disturbed” phosphorus cycle for more than a decade: humanity has discovered a huge amount of this element that ends up in waterways, and does not return to arable land.
The problem comes down to crap. Humans and livestock eat the crops and release phosphorus as a result. (A University of Iowa researcher has calculated that livestock in the state produces as much feces as the nation 168 million people.) But most of it won’t feed the plants again. Recycling can turn sludge or manure into fertilizer, but transportation and recycling is often impractical, so it can end up in the trash. warehouses and “dry stacks” no chance to boost another crop.
Or the system may be leaking: sewage, septic tanks, warehouses and eroded soil dump phosphorus into the oceans and rivers, where it dissolves to oblivion, destroying these ecosystems. For example, phosphorus runoff causes harmful algal blooms that have killed algae in Florida and starved thousands of manatees.
The Demey model determined that in 67 years, people pumped almost billion tons non-renewable phosphorus into food systems. Her team numbers are derived from statistical data from the Food and Agriculture Organization of the United Nations. Global country-by-country data reports crop yields, such as the number of wheat grown or the number of pigs and cows from 1961 to 2017. (Data for 1950–1961 are taken from Another datasets.)
Her team also took a look at usage trends. In 2017, the share of Western Europe, North America and Asia increased to nearly 60 percent of the total plant-useable phosphorus available in the soil of each region. Brazil, China and India are rapidly increasing their use to 61, 74 and 67 percent respectively. The numbers for France and the Netherlands are no longer rising because they replaced some use phosphate rock with manure; now they are about 70 and 50 percent. However, in African countries such as Zimbabwe, lack of phosphorus in the soil limits yield. Demay estimates that Zimbabwe’s mineral fertilizer use is between 20 and 30 percent, even lower than the 32 percent average for all of Africa.
For Elzer, this sheds light on global inequalities: Poorer countries have access to much less fertilizer despite needing more. And rich countries have been able to accumulate rock stocks for decades, while countries that struggle with food security cannot afford it.
This raises concerns about who will control the future of fertilizer. Nearly 75 percent of the world’s reserves come from the mines of Morocco and Western Sahara. Economists are alarmed when a commodity ends up in the hands of a few powerful people. (OPEC controls about the same share of world oil, but with 13 member states.)
And it’s not entirely clear how long the stock will last. In 2009, Cordell calculated that a global “phosphorus peak” could occur. as soon as 2030, which would leave 50 to 100 years of dwindling reserves. Today, she and Elser agree that the peak is likely to come later, though it’s hard to predict when exactly because demand could skyrocket for other uses, such as lithium iron phosphate batteries. Elzer notes that new analyzes now show a maximum supply of 300 to 400 years.