Let's hear it from the frogs!



Posted on 21 February 2002  | 
Worldwide, disturbing reports of population declines, mass mortalities and species extinctions of amphibians have been accumulating for the last two decades, so much so that the World Conservation Union (IUCN) has established a Declining Amphibian Populations Task Force.

On a global scale, South Africa has high amphibian diversity, but 23 of the nation�s frog species (or 21 per cent) are Red Data listed or, in other words, are either threatened with extinction or are likely to become threatened in the near future.

Under pressure
Although the amphibian declines are not fully understood, and several factors are implicated, there is no doubt that many populations and species are experiencing extraordinary environmental pressures. At present in southern Africa, the most important factor impacting on frog populations is almost certainly habitat destruction, brought about by urban and agricultural sprawl, wetland drainage and infilling, and pollution. Loss of frog populations is likely to have negative effects on the functioning of ecosystems because adult frogs are predators on invertebrates, and both adult frogs and tadpoles are important prey for a variety of predators.

If ever reliable baseline distribution information were necessary for a group of organisms, it is necessary for amphibians. The Southern African Frog Atlas Project (SAFAP) was launched in November 1995, with WWF-SA as one of its co-funders. The project is co-ordinated from the Avian Demography Unit (ADU) at the University of Cape Town, assisted by regional organisers in the various provinces of South Africa, and in Lesotho and Swaziland.

Frogs are generally hard to find, and even when found, tend to be difficult to identify because of variability in skin colour, markings and size within the same species. A reliable form of evidence on which to base identification, however, is by their calls, as the calls are specific to each species. Data is therefore submitted, by volunteer members of the public and by professional herpetologists, mainly in the form of audio recordings of calling frogs.

Working with grids
SAFAP aims to comprehensively cover all 110 species of frogs in South Africa, Lesotho and Swaziland, on a quarter-degree (15'x15') grid (except in the arid west where a half-degree grid is being used). There are a daunting 1 650 grid cells to be covered.

To date, about 30 000 records, including some 8 000 pre-atlas records, have been entered for 91% of the grid cells, although many of these cells will require further visits to improve the depth of coverage, ideally to record all species present. The greatest need is for more data from the arid western parts of South Africa where rainfall is both scarce and unpredictable, but where, nevertheless, several interesting species of frogs occur, and also from inaccessible montane areas.

What is in critically short supply is time. The rate of environmental destruction and change is such that, within the next few years, biodiversity must be catalogued and mapped, and effective conservation action plans put in place, or species will disappear without our even noticing.

For more information:
Christine Riley, email: criley@wwfsa.org.za

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