According to conservationists, our planet is now facing its largest mass extinction since the disappearance of the dinosaurs, with up to a third of the world's 6,000 amphibian species at risk.

Amphibians — frogs and toads, newts, caecilians and salamanders — are being affected at an unprecedented rate by habitat loss, climate change and pollution.

But added to this list is an invasive disease that’s been called the smallpox of the amphibian world: a deadly parasitic fungus known as amphibian chytrid.

Currently unstoppable and untreatable in the wild, the fungus basically causes the animal's skin to thicken. These changes in the skin are deadly to amphibians because, unlike most other animals, amphibians absorb water, oxygen and important salts (electrolytes, like sodium and potassium) through the skin and not through the mouth.

Amphibians are vanishing from the planet at a rate that far outpaces similar rates for birds and mammals.

This is particularly alarming because amphibians are considered environmental indicator species, that is, those species that are extremely sensitive to environmental change and the first to die off or decline in the face of habitat change.

The worldwide decline in wild populations of amphibians observed in the past several decades has become known as the Global Amphibian Crisis.

This crisis has hit particularly close to home at the North Carolina Zoo with some of the amphibian species on exhibit, but probably none more than the Panamanian golden frog (Atelopus zeteki).

Actually a toad, the species is now believed to be extinct in the wild because of the chytrid fungus and other factors that scientists say may be exacerbated by climate change and pollution.

The species was last filmed in the wild in 2007 by a BBC natural history unit, with the remaining few frogs taken into captivity. Since then, institutions and facilities such as the N.C. Zoo have been taking part in captive-breeding programs to further save the species.

Found in the dense rainforests of central Panama, the golden frog is a national icon and is considered a good luck charm to any Panamanian who sees it — so much so that it is frequently pictured on their lottery tickets. The frog has been steeped in the mythology of Panama since pre-Columbian times, with locals believing that when the frog dies, it turns to solid gold.

In 2010 the Panamanian government passed legislation recognizing Aug. 14 as National Golden Frog Day. This adoration has caused many people there to collect the frogs and keep them in their homes, which has, of course, further exacerbated the problem of declining numbers of frogs in the wild.

As bleak as the future looks for amphibian species like the golden frog, hope still lies in continued efforts to protect and preserve their habitats and in captive breeding programs.

Well before the discovery of the chytrid fungus in Panama, biologists began to realize that the species was in trouble.

The response was Project Golden Frog, a conservation initiative begun in the 1990s in which institutions in Panama and the United States work together to protect the species.

The golden frog is still surviving in facilities like the N.C. Zoo, but unfortunately it is not known when the species will be able to return to its natural habitat, if ever, due to the devastating effects of the chytrid fungus and other factors that researchers are just now beginning to discover.

Visitors to the N.C. Zoo can daily view as many as five Panamanian golden frogs, along with three species of similar poison dart frogs, at the park’s Forest Aviary exhibit.

Tom Gillespie works for the public affairs office of the N.C. Zoo.