Frogs sound extinction warning

DO YOU remember the African giant bullfrog?

It featured in The Herald seven years ago after the floods in Port Elizabeth prompted it to pop up in Parson’s Vlei.

Port Elizabeth is the southern-most range of this amazing creature, and the spongy Baakens River headwater area west of the city, particularly Parson’s Vlei in Bridgemead, is its refuge.

It popped up again this week in conversation as I was chatting to some experts about the recent report on the global “extinction crisis” by the US Center for Biological Diversity.

Earth is experiencing the worst spate of species die-offs since the loss of the dinosaurs 65-million years ago.

Extinction is a natural phenomenon but, as the centre notes, this usually occurs at a background rate of about one to five species per year. Scientists estimate we’re now losing species at 1000 to 10000 times the background rate, with literally dozens going extinct every day. So 30% to 50% of all species could be heading toward extinction by mid-century.

Unlike past mass extinctions, caused by events like asteroid strikes, volcanic eruptions and natural climate shifts, the current crisis is almost entirely caused by humans. Habitat destruction, alien invasive species and climate change are causing most problems.

No group of animals is more endangered than the amphibians with an estimated one third of the roughly 6300 known species at risk of extinction, the centre says.

“Because of their sensitivity to environmental changes, these vanishing frogs, toads and salamanders should be viewed as the canary in the global coal mine signaling subtle yet radical ecosystem changes that could ultimately claim many other species, including humans.”

Renowned South African herpetologist Dr Niels Jacobsen notes five threatened species in the Eastern Cape – the endemic and critically endangered Hewitt’s ghost frog, the Amatola toad, the Hogsback chirping frog, the Knysna leaf-folding frog and the kloof frog.

Only a handful of adult Hewitt’s ghost frogs have ever been seen. About 5cm long with green-brown spots and “lovely kermit feet”, as herpetologist Dr Bill Branch once described it to me, it clings to rocks in the cascade zone around little waterfalls in the Elandsberg, to where it is restricted.

Back in 2005 after devastating veld fires, together with two researchers, I visited the area, which you access up past Rocklands. The concern was that debris from the fires could have silted up the streams and suffocated the Hewitt’s tadpoles. The mission was to see if they had survived.

We did find some tadpoles and the species continues to survive, a tiny population on the edge of extinction. But for how long is unclear not least because it is surrounded by alien pine forest which of course is a tinder box for veld fires.

Looking back at my stories I am reminded that those devastating fires of late 2005 were followed by the floods of mid-2006. And that’s when the African giant bullfrog last appeared, according to environmental consultant and reptile and amphibian specialist Mark Marshall.

The species grows to a weight of well over 1kg and lives in ephemeral pans which fill with water after heavy rains but which are otherwise dry most of the time. In the dry periods it lives below ground emerging with heavy rains to mate and feed on adjacent dry ground on insects, small rodents, reptiles and other amphibians and even small birds.

Marshall says the concern is that even when studies precede development projects in the area, they will not pick up the presence of the species if it is underground.

Protected areas need to be declared on Port Elizabeth’s western rim and these should include as well the stormwater seeps that feed these pans, and monitoring to ensure they remain clear of pollution which in itself can kill off the bullfrog and other amphibians, he says.

Bridgemead resident and Parson’s Vlei watchdog Colin Urquhart says two volunteer workshops recently cleared alien vegetation from around the pan. Roads are already in place for future phases of the adjacent townhouse development and the challenge if it goes ahead will be to ensure the retention of a buffer zone around the vlei to allow the bullfrog to come out to feed.

Environmental consultant Dr Mike Cohen, former head of Eastern Cape Nature Conservation, says environmental impact assessments typically focus on existing circumstances on site whereas often a longer study over years and seasons is what is needed.

Why should we care? Besides being an early signaler of ill health in the environmental foundation upon which we, too, fundamentally rely, frogs consume large numbers of insects, many of which negatively affect human health.

Besides that, says Jacobsen – like us, they have a right to a place on Earth. “And the world would be a much poorer place without the sounds of frogs calling out their love songs on spring and summer nights.”

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