As the world's population rises, the impact of food on the climate is going up. Fuelled by resource-draining practices and our increasing demand for environmentally-damaging meat, what we eat has never mattered more to the planet's health. Food production currently contributes more than one-quarter of all climate change-causing emissions, when you take into account all the steps it takes to get food from field to plate. This includes clearing land to make space for agriculture, making and applying fertilisers, rearing animals and processing, packing and transporting the end result to reach us, the consumers.
Even if you are not currently thinking about changing what you put on your plate, in a few years we might not have much choice. As climate change continues, the amount of food we can produce from each patch of land is forecast to change – in some cooler places it will go up – but on average, globally, it is expected to go down. That means less food for a rising population. At the same time we expect an increasing number of extreme weather events due to climate change, from droughts to flooding and storms, which can devastate or reduce the size of a crop. Most worrying is that these extreme weather events are becoming increasingly connected across large areas, for example the Northern Hemisphere, potentially causing major food shortages. "The main way that most people will experience climate change is through the impact on food: the food they eat, the price they pay for it, and the availability and choice that they have," says Tim Gore, from Oxfam's Grow campaign.
But it is possible to slow these changes through the food we choose to eat. Not all foods are equal when it comes to causing climate change. Research shows that people are generally not aware of how big the differences are, and will underestimate their food's emissions. Consider two different dinner options: an 8oz steak with fries and a microwaved potato with beans. The steak dinner is over 20 times worse for the climate than the beans dinner, even after taking into account cooking.
Explaining this discrepancy between people's estimates of emissions and the true figure is something that I have first-hand experience in. While most of my career has been spent as a physicist at the University of Manchester, more recently I have applied my expertise in data science to our food chains, writing a book on the subject, and speaking to members of the public at science exhibitions.
I find people are usually surprised by the size of the difference between steak and beans, until I explain that about 5% of the calories eaten by a cow are burped out again as methane, which is a powerful greenhouse gas. The bravest then ask about the effect of the beans on our own digestive systems – might these contribute to climate change too? But it turns out that even braver researchers have studied human farts and found that eating beans does not increase the amount of methane they contain – that's one less thing to worry about at least.