Frog species and other amphibians are in massive decline throughout the world. Scientists have been trying to figure out why, writes Anthony King.
'It's not easy being green," sang Kermit the frog, and a new survey shows why. The frogs and toads of the world are dying in vast numbers. Their catastrophic decline is revealed in a global survey that found one-third of all amphibian species threatened with extinction. Scientists say the decline in amphibians is flashing warnings for the health of our environment.
The Global Amphibian Assessment found that 43 per cent of all amphibian species are in decline, with the status of 30 per cent unknown. Another 113 species have gone missing - they have not been found in the wild in recent years and are possibly extinct.
Prof Tim Halliday, who advised on the study published last Friday in Science, says "There is no single cause, as such, but the declines are due to human activities. Amphibians need clean air and water and both these things are becoming increasingly scarce."
Dr Ferdia Marnell of the Irish National Parks and Wildlife Service, an expert on Irish amphibians, says these creatures provide a useful indication of the health of both terrestrial and aquatic habitats.
Amphibians - toad, frogs, and salamanders - are the modern canaries in the coalmine. Like the collapse of the canary in the mine if toxic gas levels rose, the decline of frog populations could signal severe problems in our environment. This is because the highly permeable skin of frogs and toads is especially vulnerable to toxic chemicals and to changes in air and water quality.
Ireland has just three species of amphibians - the common frog, smooth newt, and natterjack toad. The recent "Hop to It" Frog Survey organised by the Irish Peatland Conservation Council (IPCC) recorded frogs in every county in Ireland. The most important breeding habitats were ponds, bog pools, ditches and drains.
The rarer natterjack toad is confined to a few coastal locations on the Dingle and Waterville Peninsulas of Co Kerry and one Nature Reserve in Wexford. The National Parks and Wildlife Service is currently implementing a conservation strategy for natterjacks and their numbers are being monitored by a team from University College Cork. All three species are protected under the Wildlife Act.
The question about why amphibians are in decline remains however. "The threats are complex and it's difficult to pinpoint any one cause," according to Dr Richard Griffiths of the Durrell Institute for Conservation and Ecology in Kent.
Climate change, UV radiation, widespread pollution, and disease all contribute to the amphibians' problems. The greatest threat is habitat loss, but there are other, more mysterious, causes, he says.
In the Americas, the Caribbean, and Australia, a highly infectious fungus is killing many. "Scientists don't understand why the disease has become a problem now, but chemicals and UV radiation may be making amphibians vulnerable," Professor Halliday says. The fungal skin infection was only discovered in the 1980s and Halliday says: "The exact nature of the infection is not yet known." There have been occasional outbreaks in Europe.
Halliday warns that amphibian populations come under pressure due to the destruction of hedgerows, filling of ponds, and modernisation of agriculture. "The easiest thing people in Britain and Ireland can do for amphibians is to create new ponds," he says. Griffith agrees: "The common frog and smooth newt will colonise ponds in urban and suburban areas, so long as they are in the area."
Marnell says that rural landowners should avoid the temptation to fill in ponds on their land and that suburban pond creation in Ireland can do much to provide new habitats for newts and frogs. He recommends that people allow their ponds be colonised naturally.
The Global Amphibian Assessment is hailed as the first global survey of all 5,743 known amphibians. The survey involved 500 scientists working over a period of three years. Scientists hope to use the survey results to monitor the health of species in future years.