Breton coast invaded by stinking weed

The signs point, cheerfully, to the plage (beach) but what you see at the end of the lane resembles a monstrous, waterlogged lawn or an evil-smelling paddy-field.

At low tide, the Bay of Saint Brieuc, fringed with trees and fields and dark red cliffs, used to offer mile upon mile of golden sand. It is now mile upon mile of slimy, bright-green seaweed, which stinks like a combination of dead rats and overboiled cabbage.

Over the last three decades, parts of the north Breton coast have been steadily invaded by a marée verte, or "green tide", of rapacious seaweed, stimulated by the slurry and chemical fertilisers running off the intensive pig and cereals farms of central and northern Brittany.

Everyone knows the cause; some control measures have been taken; but the monster seaweed threatens to be more monstrous than ever this year, conquering new bays and coves and even reaching the western coast of Normandy.

André Ollivro, who has a summer house on the low cliffs overlooking one of the worst-afflicted beaches, said: "This used to be one of the most beautiful stretches of sand in Brittany. After the war, people who had been deported to Germany were brought here to recover their health because the air was so pure. Look at it now. Smell it now."

Mr Ollivro plunged his leg up to the calf into a great bank of old, white, dried-out seaweed, which looked like a heap of rotten mattresses or telephone directories. Underneath the weed was still blackish-green and emitted a sickening stench. In theory, the weed is no danger to human health but two 10-year-old boys had to be taken to hospital from this beach last summer after being overcome by the smell of the rotting weed on a hot day.

"People talk of the marée noire (black tide or oil slick) which damaged the south Breton coast last year, and rightly so, but oil at least can be cleaned up," Mr Ollivro said. "The marée verte here comes back year after year, and tide after tide. By the end of August, it piles up so high in places that you can sink up to your waist."

The weed – Ulva Armoricana, one of the ulva family of seaweeds, sometimes called "sea lettuce" or "sea salad" – occurs naturally in modest, floating strands on the north Breton coast. It has been turned into a kind of sea triffid – dividing and growing by up to 20 per cent a day – by the nitrates pouring into streams and rivers.

Jean-Yves Piriou, a scientist at the French sea research institute, the Institut Français de Recherche pour l'Exploitation de la Mer, said the weed needed a combination of favourable conditions to spread out of control: a sheltered bay, warm weather, a sandy bottom and above all, an artificial supply of nitrogen.

In the winter, the weed usually disappeared, or shrank back to its normal size. In the summer, when nitrates were being poured into cereals fields and battery pig farms were in peak production – of pork, and pig-shit – the weed exploded into abnormal growth once again.

"In bays like Saint Brieuc, the weed has reached the peak of its growing potential," he said. "It is now advancing into new areas, in northern and western Brittany."

The green tide – and the failure of the French authorities to deal with it – points to a sometimes obscured fact about French agriculture. France likes to present itself as a nation of small, traditional farmers (compared to allegedly disease-generating Britain, for instance) France is, however, the second greatest agricultural, trading power in the world, after the United States.

There are small, traditional farmers in France. But the real, productive power of French farming – protected by stubborn lobbies – is in the intensive and chemical-led agriculture of Brittany, northern France and the great, cereal-growing plains around Paris. An attempt by the French government to make farmers pay more of the cost of cleaning up rivers and streams polluted by fertilisers and slurry was weakened to the point of being useless last month.

Mr Ollivro says that he has faced the same problem locally. The villages along the Saint Brieuc Bay have lost most of their tourists and property prices have collapsed by 30 per cent since the green tides ruined the beaches. But many local people, and local politicians, have been reluctant to complain because agriculture is still the dominant economic and social power in the region.

There are some signs of change, however. After the two local boys were overcome by weed fumes last summer, Mr Ollivro and a few other people launched a pressure group called Halte Aux Marées Vertes (stop the green tides). Only 300 people attended the first beach rally last September. Mr Ollivro expects 3,000 to come this year. The group has started three legal actions against "X" or persons unknown for "poisoning public beaches".

"Some local people still don't want to complain because their brothers or uncles are farmers but most people, especially the younger people, have had enough," he said. "We want our beaches back, the way they were when we remember them from our childhood."