Costs are high now, but rising oil prices will bring enormous problems for a world with appetites that it simply can't sustain

By Rosie Boycott: rosieboycott@hotmail.com

This time last year it cost me about £7.50 a month to feed a pig on my small farm in Somerset; today it's nearer £15. In a year, wheat prices have doubled, leading not only to increased bread prices, but also to demonstrations by pig farmers, who are going out of business as fast as you can fry bacon.

Almost all the food we eat - 95% - is oil-dependent, so as oil prices rise, the cost of food does too. Oil is central to fertilisers, mechanised production, transportation and packaging. However, between 1950 - when mechanisation and fertilisers transformed farming into agribusiness - and 1984, world grain production increased by 250%. The consequent cheapness of food kept inflation down and allowed for the postwar consumer boom.

For years experts have been asking what will we eat when the crises of climate change and oil depletion converge, with the possible end of our globalised food supply. Our tea and coffee and spices might still come from abroad, but what about salad vegetables, beef and fresh orange juice? Cheap oil has let the west regard the whole world as its farmyard, always seeking the cheapest place to produce and process. But last year's rate of factory-gate inflation was the highest for more than 16 years, with increases ranging from 7.5% for bread to 15% for milk, cheese and eggs and 60% for rice. Overall food inflation is 6.6%, in a year when oil prices have risen by 70%. No wonder those on the bottom of the ladder are starting to feel the strain.

Britain currently imports about £22bn worth of food and drink a year, 68% from the EU. Britain has not been self-sufficient in food since the late 18th century, but the situation is rapidly worsening. In 2006, 37% of the UK's food was imported, with London dependent on imports for 80% of its food. For the capital, a food shortage would clearly be disastrous.

We have become a meat-eating world, and in developing countries meat is seen as a sign of prosperity. However, while it takes 2kg of grain to produce 1kg of chicken, 7kg of grain is needed to make 1kg of beef. When I was a child, my family ate meat maybe once a week: now it is considered a daily prerequisite. The average Briton eats 80kg of meat a year, while the equivalent figure for Americans is 124kg - but the startling, and frightening, change is taking place in China. In 1962, there was just 4kg of meat in the average Chinese diet; by 2005 that figure was 60kg and rising.

It is not simply that we do not have enough land to grow the grain to feed the animals that in turn feed us. In the past two decades in the US, the use of hydrocarbon pesticides has increased 33 times, and yet, as soil structures weaken due to overuse and mono-crop cultivation, more crops are being lost to pests every year.

The water situation is also alarming. The world has a finite supply of fresh water yet we blithely continue to eat more meat, even though it takes between 100 and 1,000 times more water to produce 1kg of beef than it does to produce 1kg of wheat. Indeed, 70% of all fresh water is used for agriculture, so when you buy imported food, you are buying another country's water allocation. Each Kenyan green bean stem is equivalent to four litres of water from a certified "water-stressed" country. Moreover, the UN says that animal husbandry now accounts for a fifth of global greenhouse gas emissions, due to forest clearances and the methane emitted by cattle.

It's an explosive mix: rising oil prices; land shortages due to our gargantuan appetite for meat; the pressures imposed on arable land by biofuels; and the growing effect of climate change, which is rapidly reducing large areas of Africa to deserts that are no longer able to support agriculture. Put all these together, and you have a crisis that is both very real and very near.

The dominance of the supermarkets in food retailing contributes massively to our dependence and vulnerability. Rising energy prices have an immediate impact on many practices, including "just in time delivery", "warehousing on wheels" and plastic packaging - not to mention the transportation of processed foods and raw materials, which encourages the Scottish seafood outfit Young's, for example, to fly prawns to Thailand to be cleaned and de-shelled, before then flying them back home for packaging. The fuel protests of September 2000 gave us a glimpse of how even the supply of basic foodstuffs is dependent on oil: Justin King, the CEO of Sainsbury's, warned Tony Blair that we would be "out of food" within "days not weeks" if the protests continued.

In the words of Tim Lang, the professor of food policy at the University of Leeds: "We are sleepwalking into a crisis." At the very least he predicts the end of the era of cheap food, which will in itself amount to a big shift in our eating habits. But if the process of rising costs and diminishing grain supplies accelerates (as it may well do), we could be seeing actual shortages of basic foodstuffs. One report last month said that the world is only 10 weeks from running out of wheat supplies after stocks fell to their lowest level for 50 years.

It is worth noting that when we last had a food crisis, in 1939, we still had productive orchards and plenty of farmers. In recent decades our dependence on imported food has become phenomenal: half of all vegetables and 95% of all fruit consumed in the UK now come from overseas (even in September, the height of the domestic growing year, supermarkets stock predominantly South African and New Zealand apples). On average 37 farmers are leaving the land every day in Britain; there are now more people in jail than farmers. The decline in the rural labour force is a predictable consequence of the industrialisation of agriculture. Only 1% of the UK's workforce is now employed in land-related activities, compared with 35% a century ago.

It seems to me that our eating habits are unsustainable. The Stockholm Environment Institute at York University recently calculated that the UK's food and farming ecological footprint - its land, energy and sea-space use - is up to six times the UK's food-growing area.

Clearly, the government has not woken up to the looming crisis. Food and related issues straddle no less than 19 ministries. Professor Lang believes that nothing short of a radical change in our diets - away from meat and towards vegetables and grains - will solve the problem long term. Meanwhile, as he says, we are governed by the politics of Tesco - and that is truly scary.