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Food miles, climate change and consumer choice

December 2009

The UK imports 40% of its food. Part of this is due to the demand for out of season fruit and vegetables, to which we have become accustomed as consumers.

Modern shopping is complicated. Image: iStock

This can be good for our health – a more varied diet available more of the time. But it can be bad for climate change – food flown or driven to the UK contributes towards greenhouse-gas (GHG) emissions.

But what are the long-term impacts on our health and the environment? Moreover, do consumers really care? Isn’t it all about price on the supermarket shelf?

These matters have a significant bearing on our personal relationship with food, and on a nation’s ability to meet the food security agenda. If habits have to change, then we’d better know what is and isn’t good for us, the environment, and how much (small) change consumers can bear.

A project funded as part of the Research Councils' Rural Economy and Land Use (RELU) Programme, which investigates the challenges behind sustainable rural development, sought answers to these questions, and provided interesting answers.

The work focused on three vegetable groups – cabbage and broccoli, peas and beans, and lettuce and leafy salad – undertaken in three regions in the UK (Lincolnshire, Hereford & Worcester and Anglesey) and in three overseas countries: Spain, Kenya and Uganda.

The scientists developed a Life Cycle Assessment (LCA) to measure the environmental impacts and GHG emissions of the entire production chain of the vegetables, including growing, processing, retail and consumption.

Vegetables such as lettuce emitted more GHGs than did other types of crops such as wheat in each study region.

For crops such as beans, more GHGs are emitted from African crops than UK-grown crops because of transport aircraft release a large amount of GHGs (or ‘food miles’).

Obvious perhaps, but the research revealed some counter-intuitive findings.

During our winter, lettuce in Spain are grown outside. In the UK, lettuce are grown in the field in summer and in greenhouses in winter. Greenhouses use a lot of energy for heating and lighting – more GHG emissions than driving the lettuce by truck from Spain to the UK.

Lighting and heating glasshouses requires a lot of energy. Image: iStock

The situation for broccoli – grown outside in both Spain and the UK – is different again. Fresh UK broccoli released fewer GHGs than fresh Spanish broccoli, but freezing the UK broccoli increased the GHGs to the same level as Spanish produce. The LCA also showed that a large proportion of the GHGs emitted were from its storage, use and disposal in the home.

Professor Gareth Edwards-Jones from the University of Bangor, Wales, says he was very surprised by some of the results of the LCA, particularly that cooking was responsible for such a large part of the GHG emission of the vegetable life cycle.  “Several other studies have now come to the same conclusion,” he says “But when we first uncovered this aspect of the LCA it was very surprising.”

So far, so interesting. But what do such metrics mean to the consumer (or rather, what would they mean if they were available?)

A series of surveys quizzed UK consumers on factors they considered when purchasing food.

People defined local food in different ways, according to the distance it had travelled, the area where it was grown, and by food qualities as well as the way it was produced. People also recognized that buying local was not entirely free of ethical concern.

Food miles: not always bad. Image: iStock

Perhaps unsurprisingly, some consumers felt bewildered by the scientific and expert advice about health, nutrition and the environment that was available, but generally sought to engage with these issues and work out a rationale for their own decisions.

Behaviour was often determined by routine habits learned at an early age, but the majority of interviewees expressed considerable interest and support for ‘local’ food concepts but were compelled to balance this against the practicalities of convenient access to local food, at reasonable cost, and with an acceptable range of choice and variety.

These insights were reinforced by the results of a formal survey of over 1000 women with children in three UK cities (Bristol, Cardiff and Liverpool). The results highlighted three main factors: freshness, quality and price.

Price was the most important factor. When people buy vegetables, they first decide what they can afford, and then pick the best quality. Country of origin is not an overriding factor, but freshness is important.

Test for differences in the nutritional quality of lettuce grown in Spain and the UK showed that there were inconsistent differences in the chemical composition of lettuce from the two countries, but it was not possible to say
that UK lettuce are better or worse than Spanish lettuce.

Edwards-Jones thinks the project provided some real insights. “LCA analysis clearly shows that we can bring about major reductions in GHG emissions from the food system by replacing current electricity with renewable energy.”

He also doesn’t blame consumers for being confused about their buying options. “We clearly show that food miles are not a good indicator of environmental impact, and that local food is not always best.”

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