What’s happening? Emissions from global “food miles” are higher than previously believed, comprising almost 20% of total food system emissions, according to a study led by Australian researchers. The analysis estimated the carbon footprint of the global food transport system, including the transport of fertilisers, machinery and animal feed. The researchers found that, in a year, global food miles accounted for three billion tonnes of CO2 equivalent emissions – 3.5 to 7.5 times greater than previous estimates. The study also found that wealthy nations represent 12.5% of the world’s population, but generate 52% of international food miles and 46% of associated emissions. Food systems have been calculated to be responsible for a third of all global emissions. (Carbon Brief, Nature Food)

Why does this matter? In their research, the authors have renewed debate over the parameters of “food miles”.

What are “food miles”? Typically, the term has been used to measure the distance – and consequent carbon footprint – between where food is produced and where it is consumed. This study has taken a different approach to map 74 regions, 37 economic sectors and four transportation modes in order to model transport, along with the inputs needed to produce food to determine the carbon footprint of the entire food production and delivery system. In their methodology, the authors outline models of over 30 million direct trade connections, both international and national.

For example, to track the food miles involved in producing red meat for consumption in China, a traditional methodology would have noted that livestock is farmed in China and then meat is transported domestically to be consumed.

However, the new research acknowledges that while the livestock is farmed in China, the soybeans, fruits and vegetables used to feed it are grown in Brazil and the US, respectively, which in turn rely on fertiliser that is sourced from Canada. The farming machinery is imported from Germany, and its manufacturing is powered by coal from Australia and Indonesia. This method of tracking turns what was previously seen as a domestic process into one that requires an entire global system.

What can be done? In terms of its recommendations for addressing the carbon footprint of food systems, the study acknowledges that meat farming is a particularly carbon intensive form of food production responsible for nearly 40% of food system emissions.

It highlights, however, that when it comes to food miles, meat only accounts for 4% of food transport emissions. In comparison, fruit and vegetables are responsible for 20% of total food emissions, but are linked to roughly 35% of food transport emissions, due to the need for energy-intensive refrigeration through transport and their heavy weight. Refrigeration accounts for 5% of emissions across food systems.

A main focus to address emissions within food systems, therefore, must be cutting carbon-intensive products and reducing the use of carbon-emitting transport. There has been growing support in recent years for diets that reduce or eliminate the consumption of animal products. Alongside this, to reduce transport emissions a number of environmentalists have voiced support for eating locally-grown and sourced products to eliminate emissions from international food transport.

Seasonal eating – Results from the study show that sourcing food locally is a positive step, but that eliminating all international food transport would only cut food-mile emissions by 9%. For such action to be more broadly effective, it should be paired with other dietary choices, such as reducing meat consumption, and ensuring that locally sourced produce is also seasonal.

Buying local produce may reduce transport emissions, but if it’s being farmed out-of-season, it is likely to require more intensive farming inputs, such as fertiliser, water, and heating.

Overestimation? While the study has been acknowledged as a significant challenge to historical food miles classification, other academics have suggested caution in interpreting its results. Dr Ulrich Kreidenweis, a researcher at the Leibniz Institute of Agricultural Engineering and Bio-economy, stated that the study’s authors made assumptions in their models that may lead to “a strong overestimation” of food-miles emissions. For example, the study assumes that 99.4% of US domestic coal transport happens by road where, in reality, 70% of coal transport – at least part of the way from mines to consumer – happens by train.

The current situation in Ukraine and disruption to food transport is likely to increase food emissions due to waste and alternative supply measures – while having significant impacts on food security and poverty.