We all know by now that eating less meat is good for the planet - the production of meat products for human consumption leaves behind a hefty carbon footprint.
Now scientists have worked out a very simple way that canteens in schools and colleges could greatly reduce the amount of meat eaten - without actually having to cut out meat products.
Researchers conducted a study covering more than 94,000 cafeteria meal choices, and found that when the number of vegetarian options were increased – from one in four to two in four – the proportion of plant-based food purchases went up by 40-80 percent.
It may seem a little obvious that having a greater percentage of vegetarian meals in the dining selection results in more of those meals getting picked, but it's an excellent example of how simple changes can nudge us towards better habits.
In other words, cutting down our meat consumption may not necessarily mean a serious effort of willpower or a significant amount of pre-planning – just a tweak to the menus in our schools, colleges - and maybe even offices and restaurants.
"Shifting to a more plant-based diet is one of the most effective ways of reducing the environmental footprint of food," says conservationist Emma Garnett, from the University of Cambridge in the UK.
"Replacing some meat or fish with more vegetarian options might seem obvious, but as far as we know no one had tested it before. Solutions that seem obvious don't always work, but it would appear that this one does."
Overall meal sales were unaffected by the changes, the researchers report, and the biggest increase in people picking veggie options was observed in the people who had previously eaten the most meat.
The data was gathered across a series of experiments in three Cambridge colleges, carried out over the course of a year.
Besides the increase in the proportion of meat-free meals being sold, there was no evidence of any rebound effect – where diners would compensate for a vegetarian lunch with a meat-heavy dinner, for example.
While the researchers are keen to stress that they're not calling for meat to be sidelined from canteens completely, they do think "more starring roles" should be given to vegetarian options.
And the beauty of this approach is in its simplicity – consumers don't really have to think about their choices, and meat is still an option. Other possibilities under investigation from the same team include changing the pricing of meat vs vegetarian meals, and altering the order in which they appear on the menu.
Since 2016, a Sustainable Food Policy put into place at the University of Cambridge has resulted in a 33 percent reduction in carbon emissions per kilogram of food purchased, and a 28 percent reduction in land use per kilogram of food purchased. These small changes can make big differences.
"Education is important but generally ineffective at changing diets," says psychologist Theresa Marteau from the University of Cambridge. "Meat taxes are unpopular. Altering the range of available options is more acceptable, and offers a powerful way to influence the health and sustainability of our diets."
The research has been published in PNAS.