Wetlands are special places, and they have long been under threat. Estuaries, coastal marshes, inland lakes, floodplains along river valleys: these watery expanses were once abundant, covering much of the landscape, in Britain and elsewhere. Steadily, through history, their area has shrunk, as one after another wetland has been drained.

The pace of that unwelcome change has accelerated in modern times, with wetlands drying up or being drained by man as agriculture, industrialisation, urban settlements and environmental pollution have taken their relentless toll.

The loss is immeasurable. Wetlands come in many forms, but all can boast a rich and balanced ecosystem not found on dry land. All are home to myriad species of precious flora and fauna. Wildfowl and rare migratory birds may be glimpsed among the reedbeds; fish drift through the shallow waters, insects and amphibians abound. Many of the species are already endangered, and they will not thrive anywhere else.

But the benefits go beyond beauty. Wetlands do practical good. They absorb excess rainwater and - as we are belatedly discovering, now that so many have been lost - they greatly reduce the risk of flood.

As we report today (page 13), a new map shows how much further the wetlands extended in prehistoric times. It serves as a focus for a new campaign, by a partnership of conservation groups under the name Wetland Vision, to restore some of the ecological balance that has since been lost.

There are places, even in Britain today, where new wetlands could be created. And there are ways, even in our modern, industrialised world, of preserving those wetlands that remain.