When it comes to the links between our diets, our health and the environment, the research picture is wide-ranging and complex. It encompasses not just agriculture, climate science and nutrition but also questions around food choices, societal norms, aspirations and identities.
How we transport our food, store it, cook it, and how much is lost or wasted (an estimated 30% worldwide) are also key considerations in the sustainability of our food system as a whole. And widely varying scenarios across the globe mean there can be no one-size-fits-all solution – while in affluent societies excessive calorie intake has contributed to a rapid rise in rates of obesity, in the developing world more than three billion people are classed as malnourished.
The work of the Oxford Martin School’s research community seeks to inform multiple facets of this issue, contributing to both the scientific evidence base and the public discourse around healthy, sustainable diets. From fundamental changes to farming methods to the potential of alternative protein sources, our work in this area is focused on identifying solutions that will benefit both people and planet.
Meat: a key contributor to global warming
The world’s total global meat consumption currently stands at more than 300 million metric tonnes per year, having risen from seven million in 1960, and could rise by as much as 76% by the middle of this century (including a doubling in the consumption of poultry, a 69% increase in beef, and a 42% increase in pork). The rearing of livestock for meat, eggs and dairy products generates some 15% of total global greenhouse gas emissions and uses 70% of agricultural land.
A 2014 paper published in Climatic Change was the first to provide quantitative evidence that going meat-free can dramatically reduce the impact of our diets on the environment. The researchers analysed data from the diets of 65,000 meat eaters, fish eaters, vegetarians and vegans who had taken part in an Oxford-based cancer epidemiology study, and found the greenhouse gas emissions associated with a meat-based diet were approximately twice as high as those for vegans, and about 50 per cent higher than for vegetarians. As an example, if someone eating more than 100 grams of meat a day simply cut down to less than 50 grams a day, their food-related emissions would fall by a third.
On the thorny question of whether we need to stop eating meat to save the planet, study co-author Dr Peter Scarborough said people did not necessarily need to give up meat completely: just cutting down makes a big difference.
The environmental cost of 'business as usual’
Without concerted action, the environmental impacts of the food system could increase by 50-90% by 2050 as a result of population growth and the rise of diets high in fats, sugars and meat, according to an October 2018 study published in Nature.
Those impacts could lead to proposed ‘planetary boundaries’, relating to changes in land use (e.g. from forest to grazing land), freshwater use and over-application of fertilisers, among others, being surpassed, leading to instability in the natural systems upon which life depends.
Adopting more plant-based, ‘flexitarian’ diets globally could reduce the greenhouse gas emissions of the food system by more than half, the authors found. Indeed, they argued that we will fail to sufficiently mitigate climate change if we don’t change the way we eat. But the study made clear that no single solution will be enough to solve the problem: we must also improve management practices and technologies in agriculture, and halve the amount of food we waste or which is spoiled before it reaches consumers.