Kiwi study finds food-production-related emissions rise when people walk to work

Walking offers many benefits, by may come at a cost to the evironment. Photo / 123RF

Kiwi scientists have released a study which shows that walking to work can deliver a larger carbon footprint than taking the car - because of the increased food intake it requires.

The paper from the University of Otago, published in the international journal Scientific Reports, looked at a shift from passive modes of transport, such as driving, to active modes, such as walking, which could lead to an increase in food-production related emissions.

The study shows that in countries with high-calorie diets, walking for one kilometre would require additional food that would generate around 0.26kg of carbon dioxide compared with 0.21kg of CO2 for the petrol used by a car for the same journey.

The research estimates that the additional energy expenditure required to travel one kilometre ranged from 48 to 76 kilocalories for walking and 25 to 40 kilocalories for cycling.

Lead researcher Dr Anja Mizdrak said that the findings pose an important problem.

"We have a conundrum – but a solvable one. To maximise the benefit on greenhouse gas emissions achieved by increasing active transport, we need to also address dietary patterns.

"Emissions associated with active transport will be lower if walking and cycling are powered by low-carbon dietary options."

Dr Mizdrak says active transport has many advantages including more pleasant urban living, reduced air pollution, and a reduction in chronic diseases like cancer and heart disease.

"But to maximise the effect on greenhouse gas emissions achieved by increasing active transport, we need to address dietary patterns too. Emissions associated with active transport will be lower if walking and cycling are powered by low-carbon dietary options."

Co-author Dr Cristina Cleghorn says reducing our consumption of meat and shifting diets towards more vegetables, legumes, whole grains and fruits is likely to have health and environmental co-benefits.

"Given emissions associated with different food groups range widely – from 0.02 for legumes to 5.6 grams CO2-equivalents per kilocalorie for beef and lamb in one global study, consumers switching to foods with lower emissions could reduce overall dietary emissions by up to 80 per cent."

Dr Cleghorn says in high-income countries, reductions in greenhouse gas emissions are largely proportional to the magnitude of meat and dairy reduction.

"In order to reduce greenhouse gas emissions we need to encourage changes in what we eat, as well as how we travel."