Crop fields in southern Russia Leonid Eremeychuk/500px/Getty Images

Our current food system can feed only 3.4 billion people without transgressing key planetary limits, according to an analysis of the global farming system. However, reorganising what is farmed where – along with some changes in diets – would enable us to feed 10 billion people on a sustainable basis, suggests the analysis.

“We should not go any further in the direction of producing food at the cost of the environment,” says Dieter Gerten at the Potsdam Institute for Climate Impact Research in Germany, an author of the study.

In 2009, researchers identified nine so-called planetary boundaries: limits that we shouldn’t exceed if we want to maintain Earth’s life-support systems. Gerten’s team looked at the four boundaries that are relevant to farming: not using too much nitrogen, which causes dead zones in lakes and oceans; not taking too much fresh water from rivers; not cutting down too much forest; and maintaining biodiversity.

The team’s conclusion is that half of food production today violates these limits. However, this analysis is also the first to provide insights into where, geographically, these limits are being transgressed. By changing what is farmed where, the team says it would be possible to feed 10 billion people within the four limits.

This would involve rewilding farms in areas where more than 5 per cent of species are threatened; reforesting farmland where more than 85 per cent of tropical forest has been cut down; reducing water withdrawal for irrigation and other purposes where too much is taken; and decreasing nitrogen fertilisation where levels in surface water are too high. Farms could be expanded in areas where these limits are not being exceeded.

It could, for example, mean restricting fertiliser use in parts of eastern China and central Europe, and expanding it in parts of sub-Saharan Africa and the western US.

Such changes would allow the sustainable production of enough food for 7.8 billion people, roughly the current world population. Reductions in food waste and a shift away from eating meat could increase this to 10.2 billion – slightly more than the projected 2050 world population.

One big caveat is that the team assumes that the planet won’t warm by more than 1.5°C. Future studies will look at the effects of warming beyond this, says Gerten. On the flip side, the team assumes that the world relies only on existing technologies, and not on new approaches such as genome editing and using electricity from solar panels to grow food.

Journal reference: Nature Sustainability, DOI: 10.1038/s41893-019-0465-1