Mediterranean Temporary Ponds in Sardinia

Jeremy Biggs, FHT Director, reports back on the recent Mediterranean temporary ponds conference in Sardinia.

Freshwater Habitats Trust has close ties with freshwater biologists interested in ponds, small lakes and streams throughout Europe. As an organisation we’ve been instrumental in helping to increase understanding of the critical importance of small waters to freshwater life, particularly by working with partners to establish the European Pond Conservation Network (EPCN). This network allows specialists across Europe working in nature conservation and freshwater research to get together to pass on knowledge, ideas and experience to help protect ponds and their wildlife. Traditionally it’s been assumed by freshwater biologists that little things like ponds can’t be all that important compared to big lakes and mighty rivers, like the Rhine or Danube – so there’s been a big awareness raising job to do amongst technical specialists, governments and official bodies.

One of the most important types of ponds in Europe are what specialists have named Mediterranean temporary ponds. Biologists interested in these habitats recently met in Sardinia to exchange ideas and see Sardinian conservation work that’s protecting these delicate and beautiful habitats. I was able to get along to this meeting as part of my Easter holiday to experience for real these very special habitats.

The main site visit for the meeting was a place in central Sardinia called Giarra di Gesturi where the temporary ponds are locally called ‘pauli’. These ponds, which are no more than 30-40 cm deep – you can walk right the way across them in welly boots (though barefoot is nicer!) – are shallow and warm and rich in both plants and animals. At this time of the year they are covered in carpets of white flowered water-buttercups.

They have a remarkable variety of special plants and animals but you need to know your stuff to realise this: a lot of the special plants ae very tiny – just a centimetre or two high – like the tiny water fern Delicate Pillwort (Pilularia minuta). This is a plant found in only in the Mediterranean and then only in place like these small and vulnerable pools. The plant is a miniature version of species which is also threated in Britain – ours is known just as plain Pillwort. There is also an endemic tree frog, and Tadpole and Fairy Shrimps, the spectacular and special temporary pond invertebrates which cannot survive where fish occur. Both are very rare in Britain.

The Tadpole Shrimp Lepidurus apus (this one is about half grown) is a spectacular and exciting creature to find in the wild which depends entirely on ponds which dry out. Tadpole Shrimps need high quality ponds – free from pollution – and are have declined throughout western Europe as a result of land drainage and pollution. In Britain the related Triops cancriformis is one of our most endangered animals found in just two places in the country – and in only a handful of ponds – in the New Forest and on the Solway Firth.

Mediterranean temporary ponds really only survive in protected areas. They can be destroyed by a drainage ditch just a foot or two deep. With their small volumes they’re also easily damaged by pollution and the delicate balance between the wet and dry phases are vulnerable to the changing climate – at the moment no one really knows quite how changes to the weather will affect them. The better news is that in Sardinia the Giarra di Gesturi is a valued local tourist attraction, promoted by the town. This bodes well for the future of the site and the ponds, provided it is not overwhelmed by global changes. It’ll be a place that Sardinian biologists and conservationists, with help from other colleagues in the European network, will need to keep a close eye on.