Fragile habitats in chalk rivers under threat

Their water is incomparably pure; their wildlife incomparably rich. But now the rivers that flow from the great band of chalk that runs across southern England are in need of care and attention, a study has concluded.

Their water is incomparably pure; their wildlife incomparably rich. But now the rivers that flow from the great band of chalk that runs across southern England are in need of care and attention, a study has concluded.

The rivers - 161 in all - should be seen together as a unique and fragile habitat deserving special protection, says a report by the Environment Agency in co-operation with English Nature, the Government's wildlife watchdog body.

The report is the first full study of England's chalk rivers and sets out an agenda for conservation of the rivers. For although they include many of the loveliest watercourses in the country, including the Test, the Itchen, the Kennet and the Hampshire Avon, most of them face significant threats - from water over-abstraction and pollution to development and climate change.

The qualities of England's chalk rivers are well known to trout fishermen - who refer to them generically as the chalk streams - because it was on them, and on the Test and Itchen in particular, that flyfishing in its modern form was developed in the late 19th century. But they are much less well known to the general public, whose typical vision of a chalk landscape is the White Cliffs of Dover.

They emerge from the broad swath of chalk that runs in a geological crescent from Dorset in the south-west across Hampshire and the Berkshire Downs, through the Chilterns to Norfolk and on into Lincolnshire and Yorkshire.

The rivers range from the Piddle and Frome in Dorset to Driffield Beck in Yorkshire. Some, such as the Darenth and Wandle, flow through London; and in the cleaned-up waters of the latter - as reported in The Independent last week - brown trout are now flourishing.

The most remarkable feature of the chalk rivers is the quality of their water, often referred to as "gin clear".

As rainfall sinks through the porous chalk it is filtered; when it comes back up through springs, it is so pure that it is highly sought after by water companies, as it needs little if any treatment. But the rivers are also richer than any others in wildlife, above and below the surface. They support kingfishers, otters and water voles, and a profusion of aquatic wild flowers. Their waters are rich in shrimps and aquatic insects such as the mayfly, which is an important food source for trout and other fish.

"We want people to recognise chalk rivers as a key part of England's natural heritage, and as a fragile ecosystem under a tremendous amount of pressure," said Lawrence Talks, an Environment Agency fisheries officer who heads the group responsible for the report.

"The pressures on them now range from urban and infrastructure development, to pollution from intensive farming and sewage discharges."

Most chalk rivers are located in the densely populated south-east of England, where rainfall is relatively low, according to the report.

It says: "In some river catchments, there are no other sources of water for abstraction. Around 40 chalk river stretches are already under investigation for low flow problems, but climate change and increases in development and population are likely to intensify the pressure on chalk rivers and water supplies."

In a water quality survey in 2000, only 37 per cent of chalk rivers were very good quality in both biological and chemical terms, says the report.

It sets out an agenda for action with three main aims: to maintain and enhance the characteristic plants and animals of chalk rivers; to restore water quality, flows and habitat diversity; and to identify cost-effective means of restoring damaged river reaches.

The agenda calls for involvement from the Government, industry, local authorities, interest groups, landowners, and the public as a whole, as well as setting out a considerable role for the Environment Agency itself.

Water companies also had a large part to play in protecting our chalk rivers, said the agency's chairman, Sir John Harman. "They must make sure that their activities do not cause further damage to these important habitats."

ENDANGERED ECOSYSTEM

Mayfly, Ephemera danica

The largest of the upwinged flies and as big as a butterfly,fishermen copy it in flies tied with feathers, hair and silk. It usually appears for two weeks in mid-May and sends trout into a feeding frenzy.

Water crowfoot, Ranunculus fluitans

The plant that gives chalk rivers their pleasing appearance; it is brilliant emerald green with white star-like flowers, provides shelter for fish and insects and helps slow the river flow.

Freshwater shrimp, Gammarus pulex

This small crustacean swims on its side and in healthy rivers its populations can be enormous, enabling brown trout and other fish to grow to a considerable size.

Brown trout, Salmo trutta

The fish for which the classic English chalk rivers such as the Test are famous among anglers the world over: mottled brown camouflage above, and patterned below with a yellow belly and red spots.

Otter, Lutra lutra

After being wiped out by pollution in the 1950s and 1960s, otters are making a comeback across Britain and are now present in increasing numbers on some chalk rivers, such as the Itchen.

Grey wagtail, Motacilla cinerea

Strikingly coloured with a blue-grey upper-part and a yellow belly, grey wagtails are common on chalk rivers and live on abundant river flies, such as mayflies and olives flies.