What's the story with food miles?

How far will your dinner have travelled before it finds its way on to your plate this evening? And does it really make any difference if it has come from the other side of the world or the other side of the garden? More and more people are becoming convinced that the miles your food puts in are of singular importance and, in an unlikely alliance, environmentalists and some of the biggest retailers in the world have started working together to bring production closer to home.

The retailers have started investing heavily in lessening their carbon footprint, and with such enthusiasm that it is clear they now recognise that not only does an eco-friendly approach make sense, it makes money.

Much attention is being focused on food miles - the measure of the distance food travels from field to plate. According to the British department for the environment, food and rural affairs (Defra), food miles have been steadily increasing over the last three decades as our demand for strawberries in November, new potatoes in January and organic blueberries any time grows increasingly insatiable.

This year-round demand for out-of-season produce has led to food transport accounting for half the carbon-dioxide emissions of the food sector with processing, packaging and farming sharing the rest.

While there are critics of the food miles concept as a measure of the environmental impact of a food, it is self-evident that an awareness of how far the food you eat travels makes sense. Food eaten immediately after harvesting tastes better than food shipped halfway around the world, while some of the journeys our food is sent on in order to save producers money are, frankly, ridiculous.

One Scottish manufacturer ships prawns caught in the North Atlantic 8,000km to China to be hand-shelled by low-cost labour before bringing them back to Scotland to be breaded and sold as fresh local produce.

Fish caught off the Irish coast is often transported to Poland for processing, while potatoes, onions, carrots, tomatoes, courgettes, cauliflower and pretty much every other vegetable that can be grown here is both imported and exported in growing numbers.

Concerns over food's carbon footprint have seen Marks & Spencer and Tesco in particular falling over themselves to promote their environmental responsibility in recent weeks.

Earlier this year, Marks & Spencer unveiled a €300 million "eco-plan", which is admirably ambitious. Dubbed Plan A ("because there is no plan B"), it aims to make the company's operations in the UK and Ireland completely carbon neutral within five years.

The company also aims to minimise energy use, maximise the use of renewables and is mobilising its suppliers to reduce their own carbon footprint. It has committed itself to buying as much food from the UK and Ireland as possible and will double its regional food sourcing within 12 months.

It also says it will minimise the amount of food it transports by air freight - by far the most environmentally destructive mode of transport - and will label the food imported by air as "flown".

Not wanting to be left behind, Tesco Ireland, the biggest supermarket group in the country, plans to spend €30 million over the next five years in reducing its energy consumption by half - this is just a fraction of the total spend of its parent in the UK.

By 2010 there will be 100 per cent recycling of Tesco Ireland's store waste and packaging, a move which will see more than 24,000 tonnes of waste recycled each year - equivalent to the waste generated by a town of 20,000 people. It also plans to build what it describes as the most environmentally friendly store in Ireland by 2009.

The chain also plans to trial composting in all of its stores and aims to reduce packaging on its own-label products by 25 per cent by 2010. It is also developing plans to publish details of the carbon footprint on the packaging of products it sells.

Despite this flurry of activity, environmental issues remain of peripheral concern to Irish consumers, according to research carried out by Glanbia Consumer Foods. A recent study found that Irish shoppers displayed a very low awareness of environmental issues, with only 24 per cent knowing what "food miles" meant. A slightly higher 30 per cent of people surveyed were aware of "carbon footprints".

The move towards buying local produce and focusing on food miles is not entirely without negative consequences. Buying homegrown tomatoes that are grown under artificial light may actually be more damaging to the environment then buying tomatoes grown under sunlight in the south of Spain.

In New Zealand in particular, food producers are growing increasingly worried about the food miles concept: unsurprisingly, as it has the potential to destroy - or at least severely weaken - the country's export business. Around a third of New Zealand's food and drink exports are destined for EU markets 19,000km away.

"The concept of food miles is both flawed and too often promoted by those motivated by self-serving objectives rather than genuine environmental concerns," New Zealand's agriculture minister Jim Anderton said recently. "It is being used in Europe by self-interested parties trying to justify protectionism in another guise." But then he would say that, wouldn't he?