afrol News, 19 October - A poorly understood wave of extinction has hit the world's less than 6000 remaining amphibian species for years. The rapid reduction of frogs, toads and salamanders earlier was mainly confined to the Americas and Australia. A new scientific global survey however found that the frog death has now spread to Africa, in to particular Madagascar, Cameroon and Tanzania.

Over the past three years, scientists analysed the distribution and conservation status of all 5,743 known amphibian species - which include frogs and toads, salamanders, and caecilians. Of these, 1,856 - or 32 percent - are now considered threatened with extinction, according to the report. The study included 500 scientists from over 60 nations.

A reduction of the number of amphibian species has been observed by scientist for decades. This reduction was first noted in South and Central America and Australia, which is home to 207 out of the 435 most threatened species. Scientists mostly quote widespread habitation loss as the principal reason for the extinction wave, but the mostly mysterious phenomenon could also be caused by global warming, some scientists hold.

The global study provides much new knowledge regarding the size and speed of the current extinction wave of amphibians. It also concludes that the phenomenon is not defined to the Americas and Australia, but actually occurs on a global scale. Africa is turning into one of the most affected continents.

The island and eco-region of Madagascar is of special concern to the scientists. A total of 222 amphibian species are known in Madagascar, out of which 221 are endemic to the Great Island. More than a quarter of these, 55 species, are considered to be threatened, according to the study.

The extinction rate is particularly great in Madagascar's forested eastern and northern regions, where deforestation has been a grave problem. In neighbouring Seychelles, even 55 percent of all amphibian species are considered threatened. On this Indian Ocean archipelago, all species found are endemic.

A second region of concern, according to the report, is found in East Africa. In central Tanzania and in the border region between Rwanda, Burundi and Congo Kinshasa, tens of amphibian species are about to be lost. In this region, scientists are additionally confronted with poor knowledge of how many species actually exist.

In Tanzania, 157 species are known, but scientists expect that at least 50 other types of amphibians are yet to be scientifically registered in the country. In Congo Kinshasa, which holds one the most favourable climates for amphibians world-wide, hundreds of species could head into extinction while still undiscovered. No amphibian survey work has been done in Congo in the last 40 years.

The region with the highest density of known amphibian in Africa is in southern Cameroon, Equatorial Guinea and northern Gabon. This moist region is however also the area with the highest extinction rate of amphibian species in Africa. Only in Cameroon, some 50 out of the 189 known amphibian species are said to be threatened. The study further suggests that tens of species still are undiscovered in Cameroon.

The forth and last region of concern in Africa is the Upper Guinea Forest eco-region, a forest region extending from Sierra Leone and Guinea in the west to Ghana in the east. High extinction rates of amphibians had been registered in Liberia, Côte d'Ivoire and Ghana, according to the survey. Rapid habitat loss in the deforested region is believed to explain the high extinction rates here.

After birds and mammals, amphibians are the third group of species to be completely evaluated on a global scale. Environmentalists were shocked by the findings. "The fact that one third of amphibians are in a precipitous decline tells us that we are rapidly moving towards a potentially epidemic number of extinctions," commented Achim Steiner of IUCN.

The highly permeable skin of amphibians is more immediately sensitive to changes in the environment, including changes to freshwater and air quality. "Amphibians are one of nature's best indicators of overall environmental health," Russell Mittermeier of Conservation International commented on the survey. "Their catastrophic decline serves as a warning that we are in a period of significant environmental degradation," he added.

By staff writer

© afrol News

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