SHEEP graze among the heather of the northern uplands, while in the distance, down in the dales, herds of cows mooch around fields in search of the juiciest grass.

Without warning, a grouse takes to the air, emerging from cover briefly, only to disappear again among the newest heather shoots.

Dry stone walls, hedge-lined fields, the stench of manure, intrinsic features of the British countryside, built up over generations of livestock farming. But that could all change.

The issue of whether the human being, a true omnivore, should eat animals or plants, has never been more debated than now.

BSE, scrapie and swine fever, more than anything else, have focused public attention on the way animals are kept and slaughtered, swelling the ranks of vegetarians, or at least those who now only eat poultry and fish.

Vegetarianism has doubled in the past ten years. In 1984, just two per cent of the population shunned meat. The 1997 BSE crisis saw the figure soar, particularly among men. Two years later, the figure fell away as the perceived threat of contracting CJD receded. But, according to the Vegetarian Society, there continues to be steady growth with the figure approaching five per cent.

Spokesman Samantha Calvert says there are three main reasons for people becoming vegetarian. Firstly, the old guard tends to avoid meat on moral grounds. It opposes the farming methods, the way animals are kept and slaughtered and is against them being killed at all.

Secondly, a lot of new vegetarians are against eating meat on health grounds, because it can contribute to heart disease and because of the danger of CJD. "Sometimes it is self-interest. A lot of our members simply believe it is healthier not to eat meat," she says.

The final group is concerned about the environment, the way huge amounts of land is taken up for grazing, the fact that cows give off vast clouds of methane gas which damage the atmosphere, that the beasts only produce one tenth of the food they eat, when the grain would be better used feeding the world's starving.

With the young becoming increasingly animal welfare conscious, there is a view that in 30 years' time, society will have turned completely vegetarian, with far-reaching repercussions, not only for the farming industry, but also for the environment it helps shape.

"I'm not sure we would get the countryside we necessarily would want," says environmental expert and lecturer at Durham University, Dr Phil Gates, who writes The Northern Echo's Country Diary.

Take away the farm animals and the countryside would soon look very different indeed.

Without cows there would be no need for pasture, nor the hedges which contain stock in their fields. Remove the hedgerows and you take away nature's highways, natural corridors for the myriad life-forms which need cover to get around in safety. Without hedges all manner of small mammals, such as mice and voles, and birds, would fall prey too quickly to the creatures which rely on them further up the food chain.

Hawks and owls would soon dwindle in number as their main forms of sustenance become scarce.

"Hedges run all over the countryside and support all manner of wildlife," says Dr Gates. "The countryside is a rich mosaic of habitats for a wide range of species."

Farmers would be forced to consider arable crops, huge swathes of corn, wheat and barley, or field after field of peas and beans, vast prairies of featureless monotone, devoid of walls, fences, shape and colour.

"If you take animals out of the eco system there will be no animal dung," says Dr Gates. Without the animals to produce this natural fertiliser for the land, farmers would have to use nitrogen-based products which would end up polluting ponds, streams and rivers, encouraging algal blooms which can kill fish and other water creatures.

Take the sheep off the moors and the grass would become course and unkempt, scrubland rather than pasture. "At Durham's Botanic Gardens we use sheep to graze rather than cut the grass. It maximises wildlife diversity and doesn't damage the trees accidentally. They are like living lawnmowers," Dr Gates says.

Global warming would allow invasive species of tree, such as birch and sycamore, to take over the moors. It would also allow arable crops on the tops, replacing the heather which currently flourishes there. Take the grouse out of the heather and without the constant grazing they do, the plant would become woody, devoid of flowers.

"It's a fine art maintaining the moorland," says Dr Gates. "It's something people don't think about. They think about it in terms of human nutrition and animal welfare, but not impact on the environment."

Gone forever would be the tapestry effect of the fields, the hallmark of British agriculture, particularly in North Yorkshire, County Durham and Northumberland.

"It would look like a wilderness and I don't think people would want that," adds National Farmers Union spokesman Rob Simpson. "People like how we farm the uplands and, if there were no farmers to look after them, it would alter the landscape of the hills utterly. You would not have any grass, it would revert to scrub. There would be no need for the hedges or the walls because there would be no livestock to keep in."

Hundreds of rural communities rely on hill farmers for their survival. "Our villages would be decimated and the market towns, which feed off the rural communities, would go," Mr Simpson claims.

This would be followed by a decline in the allied industries; seed and feed merchants, agricultural machine businesses. The rot would then hit rural post offices, shops and pubs. Tourism would dwindle because there would be no reason to visit the countryside. Visitors would not want to stay in a wilderness.

"It just goes on and on," he says. "Take away the livestock and you would totally change the make up of our rural communities."

The countryside exists as it does because of a delicate symbiotic relationship between man, beast and nature, built up over centuries, which could be lost in a single generation. Its future rests in human hands.