Vendors unload crates of tomatoes from the back of a truck at a market in El Salvador

Domestic and international transport of food accounts for a large proportion of food-system emissions.Credit: Camilo Freedman/SOPA/LightRocket/Getty

Transporting ingredients and food products accounts for nearly one-fifth of all carbon emissions in the food system — a much bigger slice of the emissions pie than previously thought, according to the first comprehensive estimate of the industry’s global carbon footprint1.

Clearing land for farming, raising livestock and moving food to and from shops adds a large amount of greenhouse gas to the atmosphere. The United Nations estimates that growing, processing and packaging food accounts for one-third of all greenhouse-gas emissions. This has led to an explosion of studies looking into how food systems impact the climate, from causing damaging land-use changes to releasing greenhouse gases, says Jason Hill, an environmental scientist at the University of Minnesota in St Paul.

But the complexity of the food system has made it challenging to measure how much carbon dioxide in the atmosphere is a direct result of the system’s emissions, particularly those from transportation. Previously, most studies underestimated emissions because they focused on only those generated by moving a single product — such as a chocolate bar — to and from the shop. This method tends to miss the multitude of other trucks, ships and aeroplanes involved in gathering all the ingredients needed to make the bar in the first place, says Li.

Unequal emissions

Hoping to close this gap, Mengyu Li, a sustainability researcher at the University of Sydney in Australia, and her colleagues amassed data from 74 countries and regions, and looked at where the food came from, where it went and how it moved from one place to the next. They found that, in 2017, food transportation added emissions equivalent to 3.0 gigatonnes of CO2 to the atmosphere, up to 7.5 times what was previously estimated (see ‘Food transport and production emissions’). The research was published in Nature Food on 20 June.

Source: Ref. 1

Wealthy nations were responsible for generating nearly half of international food-transport emissions, despite accounting for only around 12% of the global population. Low-income countries — where around half of the global population lives — generated just 20% of international food-transport emissions.

This difference arises in part because wealthy nations are more likely to import food from around the world. They also use refrigeration when moving fresh fruit and vegetables, which is extremely carbon-intensive. Moving fruit and vegetables generated twice the amount of CO2 produced by growing them.

But the results don’t mean that people should try to limit the amount of plants in their diet, says Nina Domingo, a sustainability researcher at Yale University in New Haven, Connecticut. Many studies have shown that plant-based diets are better for the environment than consuming large amounts of red meat, because livestock need a lot of land and burp out greenhouse gases. Reducing the consumption of red meat and eating food produced locally could help wealthy countries to lower their climate impacts, researchers say.