If you've ever played around with one of those carbon or water footprint calculators, you probably know that meat production demands a lot from the environment — a lot of oil, water and land. (Check out the infographic we did on what goes into a hamburger last year for Meat Week.)
But have you thought about your meat's phosphorus footprint? Probably not.
That's why Geneviève Metson, a doctoral student in natural resource science at McGill University in Canada, did the math for you. She wanted to find out how much of the phosphorus that's mined and turned into supplements for animal feed or fertilizer to grow feed crops goes to the meat industry.
Pretty unsurprisingly, she found that meat consumption is driving much of the phosphorus use in the food sector. And, she argues in a paper published in the journal Environmental Research Letters, the heavy phosphorus footprint of meat is good reason to eat less of it, given that phosphorous is a finite resource that might become scarce one day.
"Changes we can make in our diet to decrease the demand for mined phosphorus can also decrease the use of other resources," Metson tells The Salt. "We need to manage our food system in an equitable and sustainable way, and we need to look at many resources and priorities simultaneously."
But not everyone agrees phosphorus needs to be a top concern for food security.
"Phosphorus is pretty far down the list of things we're going to suddenly run out of," Steven Van Kauwenbergh, principal scientist and leader of the Phosphate Research and Resources Initiative at IFDC, an international food security and agriculture organization, tells The Salt.
So what is this phosphorus stuff, you say? It's an element that's mostly locked up in rocks in the ground – in this inorganic form, it's called phosphate.
It's an essential nutrient for humans and plants, and much of the world's phosphate gets processed into phosphoric acid to make fertilizer that helps plants grow quickly. Mining more of it from deposits around the world has helped fuel the huge increase in global food production. Phosphate production in 2012 was 220 million tons, up from 165 million tons in 1994.
In the last decade or so, inspired by the conversation about peak oil, a few environmental researchers began talking about the possibility of peak phosphorus and the dangers that a decline in such a critical resource would pose to food production. But even those researchers acknowledged that the estimates of global phosphate reserves — and how long they'll last — were fuzzy.
So the IRDC, which helps farmers in developing countries improve their harvests with fertilizer and other technologies, asked Van Kauwenbergh to do a thorough assessment of world reserves. His report, released in 2010, offered radically higher estimates of how much phosphate was available, and estimated that with current rates of production, phosphate rock reserves will be available for 300 to 400 years.
Other industry analysts agree that there's plenty of phosphate to go around for a long while.
"Peak phosphorus is a total myth, and I don't think it's anything to worry about in our lifetime," says Juan von Gernet, a senior consultant on fertilizers for CRU, a commodities research and consulting firm in London. "There is a huge amount of phosphate in the land, and if we run out of that, there are a lot of unexplored areas on the seabed which can be extracted if required."
Van Kauwenbergh also takes issue with Metson's suggestion that using lots of phosphorus to feed people is a bad thing.
"The people in countries with high [phosphorous] footprints have the opportunity to choose lifestyles and healthy diets," he says, and those diets mean more meat. "Now it seems these scholars would have us believe this approach is wrong."
Still, environmental researchers say that any resource we're entirely dependent on will eventually run out.
"We should definitely start to approach questions about decreasing our global demand for phosphorus," says Tina Neset, an environmental researcher who studies phosphorus at Linköping University in Sweden.
Another reason to do so, she says, is that phosphorus and nitrogen from fertilizer runoff are responsible for a very current environmental problem: polluting waterways with too many plant nutrients. That can cause algae to bloom too much and deplete oxygen levels underwater — a state that can suffocate aquatic life.