KEY POINTS:
Take a look in the average supermarket trolley and the food there will probably have travelled farther than most people clock up in a decade.
A selection of just 26 items can have covered a total of 150,000 miles before reaching the British kitchen. With beef from Brazil, beans from Kenya, apples from New Zealand, chicken from Thailand and strawberries from Spain, shoppers can enjoy year-round produce.
But with such astonishing "food miles" being accumulated, it is little surprise that their environmental impact is coming under scrutiny and sparking a backlash. Already, the major supermarkets are crawling over each other to highlight their "locally sourced" produce, while Marks and Spencer has begun labelling air-freighted products with logos of aircraft.
Yet, some startling new research is emerging that shows food miles might not be as bad as consumers have been led to believe. Analysis of the industry reveals that for many foods, imported products are responsible for fewer carbon dioxide emissions than the same foodstuffs produced in Britain.
Even products shipped from the other side of the world emit fewer greenhouse gases than British equivalents. The reasons are manifold. Sometimes it is because they require less fertiliser; sometimes, as with greenhouse crops, less energy; sometimes, as with much African produce, the farmers use little mechanised equipment.
The findings are surprising environmental campaigners, who have, until now, used the distance travelled by food as the measure of how polluting it is. One study by Lincoln University, in New Zealand, found that 2849kg of carbon dioxide is produced for every tonne of lamb raised in Britain, while just 688kg of the gas is released with imported New Zealand lamb, even after it has travelled the 11,000 miles to Britain.
Researchers and farmers in Britain have raised doubts over the accuracy of the New Zealand figures, but they concede that sheep farming in New Zealand is more efficient. "They have slightly better weather," said Professor Gareth Edwards-Jones, from the department of agriculture at Bangor University, in Wales. "This means their grass can grow for longer and they don't have to give their sheep as much feed as they do in the UK." With meat in the UK, there is also a supermarket issue. Each of the supermarkets runs its own abattoir, so if you sell your lamb to Tesco, you have to send your lamb to Tesco's abattoir, even if you pass several local abattoirs on the way.
As a result, the meat picks up a huge amount of 'in-Britain' food miles from farm to abattoir then to packaging before it gets to its final destination. In New Zealand, where land is more plentiful and the climate is milder than Britain, farming is less intensive. On the extensive rolling fields of Pigeon Hills sheep farm, 40 miles from Nelson, the lush grassland needs little fertiliser to provide food for the livestock.
Farmer David McGaveston, 55, rears more than 10,000 sheep and 500 beef cattle for export to the UK. Mr McGaveston uses small amounts of hay to help supplement his sheep through the cold winter months and sends his lambs to be slaughtered and packaged at a plant just 40 miles away. Most of the electricity used is also supplied from a hydroelectric plant, which has minimal carbon dioxide emissions. He said: "I understand the debate that is going on over food miles in the UK at the moment, but if we really are producing meat with less carbon dioxide then that is surely a good thing."
Figures from the Lincoln University study also revealed that both dairy products and apples imported from New Zealand had less of an impact on the environment than those produced in Britain. Professor Caroline Saunders, who led the research, said: "Food miles are a very simplistic concept, but it is misleading as it does not consider the total energy use, especially in the production of the product."
But other studies of fruit and vegetable production have revealed a more complex picture. New research by the centre for environmental strategy at Surrey University has shown that British apples are better for the environment during autumn and winter, but in spring and summer it is "greener" to import them. Dr Llorenc Mila i Canals, of Surrey University, said: "By May, apples harvested in Britain have been kept in refrigerated storage for more than six months, which uses a lot of energy. At that point, it becomes better to import from New Zealand."
He has also found similar results for the production of lettuces, which showed that the energy used to produce out-of-season lettuces in winter in Britain was greater than importing lettuces from Spain. He added: "If you are producing lettuce in a heated glasshouse in the UK, the amount of energy you are using is huge, so in that case buying British produce over winter is a bad idea."
Similarly, British farmers who grow tomatoes and strawberries often rely on heated greenhouses to produce crops outside the short fruit season in Britain. Dr Adrian Williams, an agriculture expert from Cranfield University, in Bedfordshire, said: "If you produce something in an unheated greenhouse abroad or in a field, you make a considerable saving, as you are not having to use large amounts of energy heating a greenhouse. You could expect there to be a difference even if you allow for the transport from Spain."
Earlier this year, Mr Williams revealed that roses grown in Kenya produce just 17 per cent of the carbon dioxide released by flower-growers in Amsterdam, Holland. Importing beans by air from Uganda or Kenya is also more efficient. Professor Edwards-Jones explained why: "In Uganda, they tend to have small farms that export beans. They don't use tractors, as it is all done by hand, they use cow muck instead of fertiliser and don't use high-tech irrigation systems." For some products, however, it is better to buy British.
Onions, for example, produce 14kg per tonne less carbon dioxide than those imported from New Zealand. What is clear, is that the so-called "carbon footprint" left by a product is more complicated than simply looking at the distance it has travelled. Food miles have become the villain in the environmental debate over the global food market, with campaigners counting every mile their organic blueberries and sugarsnap peas have travelled.
But even the method of transport is generating controversy. Some researchers claim shipping is better than air freight, but others insist that for perishable goods, packing them into a plane for a quick journey is better than refrigerating them on a cargo ship. Air freight contributes just 0.1 per cent to Britain's carbon dioxide emissions.
The disagreement has led to the Government stepping in. Last week, the Department for Environment, Food and Rural Affairs announced it was developing a standard carbon calculator that all manufacturers and retailers could use to label their products.
But a study by Bangor University is set to complicate matters further. Researchers have found that the number of times a patch of soil is ploughed, and even the type of soil a vegetable is grown in, radically alters the amount of greenhouse gases released into the atmosphere. Indeed, calculations of carbon dioxide emissions could also include the footprint left by employees involved in the production of food. Per capita carbon dioxide emissions in Britain are 9.2 tonnes, while for Kenya the figure is 0.2 tonnes and for Uganda it is 0.1 tonnes. By this method, importing from Africa would be far less environmentally damaging.
