Campaigners want to see chalk streams recognised "among the rarest and most important habitats on Earth".

Only around 200 are known to exist worldwide - 85pc of which are in England, and many are in Norfolk, including the Babingly, Glaven, Gadder, Ingol, Hun, Stiffkey, Tiffey, Wissey and Wensum.

They support more species of plants than any other English river type, and provide vital habitats for threatened wildlife including water vole, brown trout and white-clawed crayfish.

But, despite their global importance, most are in poor condition with over-abstraction, sewage discharges, agricultural pollution and climate change increasing the pressure on these fragile ecosystems.

The River Glaven is one of Norfolk's rare chalk streams (Image: Newsquest)

A bill was introduced to Parliament on February 25 asking the government to nominate the UK's chalk streams as a serial UNESCO Natural World Heritage Site, to highlight their importance, strengthen their protection and help unlock funding and research to support their recovery.

And a letter to environment secretary Emma Reynolds has been signed by 50 MPs and peers including South West Norfolk MP Terry Jermy, Waveney Valley MP Adrian Ramsay, and the Bishop of Norwich, the Rt Rev Graham Usher.

The letter says chalk streams are "among the most biodiverse and ecologically significant freshwater ecosystems in the world", which are "as precious to England as the Great Barrier Reef is to Australia or the Amazon Rainforest to South America".

"Yet despite this global significance, the majority of our chalk streams are in a perilous state," it adds.

"Only one in six currently meets 'good ecological status', and not a single English river is in good overall health. Over-abstraction is causing many chalk streams to run dry during summer months, while water quality continues to decline due to sewage discharges and agricultural pollution, with devastating consequences for wildlife.

"Restoring and protecting our chalk streams is a matter of global importance.

"We therefore urge you to begin the process of nominating the UK’s chalk streams as a serial UNESCO Natural World Heritage Site. Such designation would formally recognise their international significance, strengthen long-term protections, and help galvanise public engagement and investment in their recovery and restoration."

The Rt Rev Graham Usher, Bishop of Norwich (Image: Diocese of Norwich)

Bishop Graham said: “People are rightly horrified by the destruction of rainforests thousands of miles away – but sometimes seem less concerned about collapsing ecosystems almost literally on our doorstep.

“Christians are called to advocate for God’s creation. In our nature-impoverished land, this means protecting our heritage of natural wonders, including precious chalk streams.”

South West Norfolk MP Terry Jermy (right) has backed a campaign to nominate the UK’s chalk streams as a UNESCO Natural World Heritage Site (Image: Terry Jermy)

Mr Jermy added: “England’s chalk streams are among the rarest habitats in the world and a true natural treasure. 

“These rivers are as rare and important as the Great Barrier Reef, and are a large driver of tourism, which is fundamental to rural economies like ours, but instead of being protected, they are being polluted, dried-up and ignored.

“I’m calling on the government to recognise chalk streams as a jewel in the crown of our natural heritage by nominating them as a UNESCO Natural World Heritage Site, giving them the status and protection they deserve for future generations."

Campaigners are also urging the government to give chalk streams planning protection by listing them alongside ancient woodland as an irreplaceable habit in the National Planning Policy Framework, and to reinvest fines from polluting water companies into a fund for chalk stream restoration.

© Norwich Evening News