To answer this question Emily Cassidy and colleagues from the University of Minnesota re-examined agricultural productivity, calculating the number of people fed per hectare of land, rather than the conventional measure of tonnes of food produced per hectare. “We wanted to investigate how crop allocation impacts our ability to feed people on the cropland currently under cultivation,” said Cassidy.

Using previously gathered satellite images and global census data, the researchers were able to map the global extent and productivity of 41 major agricultural crops. They used trade statistics to calculate how much food was exported or imported by each country, and employed crop statistics to determine what percentage of crops were used as animal feed, and for non-food uses (biofuels and industrial).

Immediately Cassidy and her colleagues found that one quarter of the crops we harvest are fed to animals. And since these crops, for example, maize, soybeans and oil seed, happen to be some of the most calorie-rich, they represent over half of the protein produced and more than a third of the calories. Meanwhile, biofuels and industrial crops gobble up almost 10% of the calories that we currently grow. “More crops than we originally thought are going into animal feed, which has a huge impact on global calorie availability,” said Cassidy.

But this calorie distribution is not evenly spread. The top meat-producing countries are China, the US and Brazil. And when you look at individual consumption, the biggest meat- and dairy-eaters are people in the US, the UK, France and Germany. “In these countries, the per capita consumption of animal products is over 1000 calories per day, almost one third of their dietary intake,” explained Cassidy, whose findings are published in Environmental Research Letters (ERL).

So what would happen if we only grew crops for human consumption? Cassidy and her colleagues calculate that we could, in principle, increase the available food calories by 70% – enough to feed an additional 4 billion people. As a result, many of us would have to change our diet and start eating more grains, legumes and vegetables. Animal products would diminish significantly, and only come from grass-fed or wild-caught animals.

If that sounds too drastic then the team also shows that simply cutting out beef and relying only on chickens and pigs for animal products would free up enough calories to feed an additional 357 million people – more than the population of the US.

So are these findings enough to change the way we eat? “I’m an omnivore,” said Cassidy, “but since starting this research I have been cutting animal products out of my diet, and experimenting more with vegetables and legumes. But I do confess I have a hard time cutting out cheese.”

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