It has been suspected for some time that global warming may cause widespread amphibian extinctions. In a study published in 2006 by J. Alan Pounds suggested that many harlequin frog species (Atelopus) across Central and South America have disappeared due to deadly infectious diseases spurred by changing water and air temperatures.
At one time the Harlequin Frog (actually a toad) was thought to be extinct. In 2003 the Harlequin Frog was rediscovered in the primary rain forest of the Rainmaker Reserve on the Central Pacific Coast of Costa Rica.
“Disease is the bullet killing frogs, but climate change is pulling the trigger,” said Pounds, lead study author and resident scientist at Costa Rica’s Monteverde Cloud Forest Preserve.
“Global warming is wreaking havoc on amphibians and will cause staggering losses of biodiversity if we don’t do something fast.”
The World Conservation Union (IUCN) has listed this frog as Critically Endangered and facing an extremely high risk of extinction in the wild, because most of them have disappeared since 1988. In 1996, in fact, scientists feared that all of the more than one hundred populations known to exist in Costa Rica were already gone. Seven years later, however, a tiny population was discovered at Rainmaker Reserve.
About two-thirds of the 110 known harlequin frog species are believed to have vanished during the 1980s and 1990s. The primary culprit, Pounds suggests, is the disease-causing chytrid fungus Batrachochytrium dendrobatidis.
Amphibian skin is extremely thin, which makes frogs acutely sensitive to even minor changes in temperature, humidity, and air or water quality. It also makes frogs more susceptible to chytrid fungus.
The new study suggests that temperature extremes may have previously helped keep the deadly disease in check. But new climate cycles are now moderating those annual temperature swings.
Global warming has increased evaporation in the tropical mountains of the Americas, which in turn has promoted cloud formation, the study reports. That cloud cover may have actually decreased daytime temperatures by blocking sunlight. At the same time, it may have served as an insulating blanket to raise nighttime highs.
Pounds believes the combination has created ideal conditions for the spread of the frog-killing fungus, which grows and reproduces best at temperatures between 63° and 77°F (17° and 25°C).
Extraordinary Video from Rainmaker Reserve