Sixty years ago, the great popular naturalist Sir Peter Scott, the David Attenborough of his day, founded a wildlife refuge that was to become one of the world's most celebrated nature reserves. He chose a site that, every winter, attracted a spectacular congregation of waterfowl, including thousands of white-fronted geese and Bewick's swans migrating from arctic Russia to escape the northern freeze. The location was Slimbridge in Gloucestershire – on the banks of the Severn estuary.

Slimbridge shows instantly why the gaping mouth of the Severn is special in wildlife terms. On the warm western edge of Europe, the estuary is a winter haven not only for wild swans and geese but for many thousands of wading birds from all over the continent, such as dunlin and turnstone, oystercatcher and ringed plover.

The ecological importance of this amazing, 86,000-acre bird table has long been recognised by the British Government. The estuary is protected several times over: it is dotted with individual sites of special scientific interest, and the area as a whole is protected by the international Ramsar convention on wetlands, and the European Union's Birds Directive. Only two weeks ago, the Department for Environment, Food and Rural Affairs applied for the estuary to be listed as a Special Area of Conservation under the EU's Habitats Directive – this time for its fish.

Now a minister from another government department puts a sudden question mark over the whole thing. John Hutton's announcement of a feasibility study into a Severn barrage poses a cruel dilemma for environmentalists. For the estuary potentially holds riches other than wildlife: the tidal power produced by turbines in a barrage might provide a quite staggering amount of renewable electricity to help Britain's fight against climate change.

Yet the change in the tidal regime may well have a drastic effect on the ecology on which the estuary's remarkable bird life depends. As the imperative of combating global warming becomes ever clearer, the case for the proposed barrage will get stronger. This is an issue where inventive compromise is called for, so that in trying to save the planet we do not destroy our environmental treasures.

(By Michael McCarthy, The Independent, 26/09/2007)