Pollution damages rare UK plants

By Alex Kirby
BBC News Online environment correspondent

Stoneworts tell us something about how plants first inhabited the land

An ancient UK plant that lives underwater is suffering "a catastrophic decline", conservationists say.

Plantlife International says stoneworts are struggling to survive a tide of pollution caused by nutrients spreading through the areas they inhabit.

It says 17 of the 30 stonewort species found in the UK are now regarded as nationally rare or even extinct.

Even plants in protected areas are not immune to the damage from pollutants, such as nitrates and phosphates.

Competing species

Stoneworts are so called from the lime that encrusts them: most, instead of using cellulose for structural support, build an external skeleton made of calcium carbonate.

On the basis of fossil records, they have been thought for a long time likely candidates to be the evolutionary origin of land plants.

They grow entirely under water, and when conditions are favourable can form dense "meadows".

Very sensitive to pollution, stoneworts are highly accurate indicators of water quality.

Now, 76% of their important UK sites are affected by pollution. They are being assailed by a combination of phosphates, from washing powder, and nitrogen, from fertilisers, which are flooding into water habitats.

The chemicals lead to eutrophication, a process that involves the unnaturally vigorous growth of other, competing species that flourish to the disadvantage of the stoneworts.

'Great risk'

Plantlife says even key sites which enjoy formal protection as parts of nature reserves or sites of special scientific interest, the most important conservation areas, are being damaged by the pollutants.

A Plantlife report, Important Stonewort Areas, lists 118 nationally and internationally important wetland and aquatic sites in the UK, most of them protected as SSSIs.

Despite this, Plantlife says, more than 75% of the sites remain at great risk from nutrient pollution, which it calls the single most important threat to wetland areas in the UK.

Nutrient pollution was implicated in a recent report by the United Nations Environment Programme as the reason for the emergence of marine "dead zones", sea areas starved of oxygen and bereft of life.

The report said these zones would be a greater threat than overfishing in the course of this century.