Broads are home to rare plants and animals
A quarter of the UK's rarest plants and animals are found in the Norfolk and Suffolk Broads, according to a survey.
The University of East Anglia (UEA) researchers believe it is the highest concentration of such species found in one area, including some that do not appear anywhere else in Britain.
But they also identified more than 60 species now considered extinct.
The findings will be used to help protect wetland habitats that could be vulnerable to future climate changes.
Andrea Kelly, an ecologist with the Broads Authority which manages the wetlands and commissioned the study, said even the experts were surprised at the diversity they found.
"We've always known that the Broads is an absolute wildlife hotspot but we were blown away by the amount of species.
"We've got over 11,000 species in the Broads and so many of those, over 1,500, are rare - and many of those, if the Broads didn't exist, wouldn't be here.
"So the Broads is a very special place and has so many rare species," she said.'Vulnerable'
The research carried out by UEA is believed to be the first complete audit of exactly what lives in the Broads. It combined the most recent data with other uncollated records dating back to the 17th Century.
Some of the rare species found in the area, such as the swallowtail butterfly, are well documented.
But hundreds more species thought to be there haven't been recorded in over two decades - a sign they could have disappeared.
One of the researchers, Dr Hannah Mossman, said many of the animals living in the Broads were at risk and could be particularly affected by any future changes in sea levels.
"Very few of them are able to tolerate changes in salinity. They ... nearly all require fresh water conditions so they're very vulnerable to changes in sea level which might cause increases in the salt in the water, " she said.
"They're also vulnerable to, potentially, to drying out if we have dry autumns and dry winters, and they're vulnerable to higher temperatures in the summer potentially as well."
The study also found some species had recovered in number in recent years including the crane, otter, bittern and marsh harrier.
The fen raft spider has recently been reintroduced to the Suffolk Broads and the fen mason wasp, which was formerly regarded as extinct in Britain, was rediscovered in the Norfolk Broads in 1986.
Although the Norfolk and Suffolk Broads make up only 0.4% of the UK, Ms Kelly said there were a number of reasons why it was home to so much wildlife.
"Factors include the presence of water, with large rivers flowing to the sea, and the wet peat soils. Water is a provider of life, the ditches, pools, lakes and fens are the places that wildlife seeks out," she said.
"The important thing, though, is people. People have been managing the Broads for centuries, digging peat, cutting reed beds, digging drains, managing water levels and creating places for wildlife."