For years now, the medical community, including the U.S. Centers For Disease Control and Prevention (CDC), have been warning that antibiotic-resistant bacteria are on the rise. The problem is becoming serious as antibiotic use has become widespread and commonplace, with bacteria evolving resistances at an ever-greater rate.

A new study recently published in the New England Journal of Medicine has now shown that while human overuse of antibiotics is a large contributor to the problem, the use of antibiotics for livestock and agriculture is overwhelmingly the cause of antibiotic-resistant bacteria.

The study found that 80% of the antibiotics used in the U.S. are for agricultural and aquacultural uses. The drugs are commonly fed or injected into livestock in order to increase food production.

“It’s about increasing the efficiency of food so you can reduce the amount of grain you feed the cattle,” said Aidan Hollis, co-author of the study and an economica professor at the University of Calgary. “It’s about giving antibiotics to baby chicks because it reduces the likelihood that they’re going to get sick when you cram them together in unsanitary conditions.”

The study’s authors warn, however, that a continued, unchecked increase in the number of antibiotic immune bacteria could lead to a global health crisis. Hollis suggests in the paper that a tax on antibiotic use for non-human purposes could help curb the problem, believing that a ban on agricultural use of antibiotics may be hard to implement.

The U.S. Food and Drug Administration (FDA) took up the issue earlier this month, announcing its plan to phase out the use of some antibiotics (the ones most important for humans) in food animals. The FDA’s plan calls for pharmaceutical companies to voluntarily re-label their antibiotics to prevent unnecessary use on farms.

“These methods are obviously profitable to the farmers, but that doesn’t mean it’s generating a huge benefit,” said Hollis. “In fact, the profitability is usually quite marginal.

“The real value of antibiotics is saving people from dying. Everything else is trivial.”