They say the list will help them to provide proper protection for fungi, which are often missed by wildlife surveys.

Experts say even the precise number of fungi species remains uncertain.

The list contains details of more than 500 Ifas in England, Scotland, Wales and Northern Ireland.

Constant finds

It has been compiled by three groups - Plantlife, the Association of British Fungus Groups, and the British Mycological Society.

They say no-one has known till now where the UK's best fungus sites are, apart from some well-known ones like Epping Forest on London's eastern outskirts.

Plantlife says a conservative estimate of the number of fungi species is about 12,000, with from 20 to 30 new species being discovered every year. But it believes the real number could be closer to 20,000.

Martin Harper of Plantlife said: "Fungi are of tremendous environmental importance, yet until now we have been unable to care for them properly because we simply have not had the relevant information.

"This interim list of Ifas will help target conservation efforts to ensure that key sites get proper protection.

"We also hope it will encourage further recording to improve our knowledge of this extraordinary group of organisms."

Dependent plants

Dr Harper told BBC News Online: "We've been without this information till now because fungi are an amazingly under-recorded group.

"They're pretty much missed out in traditional nature conservation, as they're hard to spot.

"Normally all you see is the fruiting bodies. A lot of the time the fungus is lying dormant with nothing to see.

"They're of fundamental ecological importance both because they recycle nutrients, and because they have close associations with plants, enabling them to fix the nutrients they need for growth.

"For example, bluebells need 40 mycorrhizal associates in order to grow.

Encouraging growth

"Only a handful of sites of special scientific interest have been listed for their fungi.

"What we need to do is to help landowners and farmers to manage their land sympathetically - leaving dead wood in place, and not using herbicides."

The compilers of the list received funding from English Nature, the Countryside Council for Wales, and northern Ireland's Environment Heritage Services.

Images copyright and courtesy of Bob Gibbons/Natural Image