El Nino killed Costa Rican toad, not global warming

March 2nd, 2010 - 3:04 pm ICT by ANI  

Washington, March 2 (ANI): A new study has determined that global warming not kill the Monteverde golden toad of Costa Rica, an often-cited example of climate-triggered extinction, but the culprits were El Nino, combined with a pathogen.

The toad vanished from Costa Rica’s Pacific coastal-mountain cloud forest in the late 1980s, the apparent victim of a pathogen outbreak that has wiped out dozens of other amphibians in the Americas.

Many researchers have linked outbreaks of the deadly chytrid fungus to climate change, but the new study asserts that the weather patterns, at Monteverde at least, were not out of the ordinary.

The role that climate change played in the toad’s demise has been fiercely debated in recent years.

The new study is the latest to weigh in.

In the study, researchers used old-growth trees from the Monteverde Cloud Forest Reserve to reconstruct moisture levels in that region over the last century.

They expected to see global warming manifested in the form of a long-term warming or drying trend, but instead discovered that the forest’s dry spells closely tracked El Nino, the periodic and natural warming of waters off South America that brings drought to some places and added rainfall and snow to others.

The golden toad vanished after an exceptionally dry season following the 1986-1987 El Nino, probably not long after the chytrid fungus was introduced.

Scientists speculate that dry conditions caused the toads to congregate in a small number of puddles to reproduce, prompting the disease to spread rapidly.

Some have linked the dry spell to global warming, arguing that warmer temperatures allowed the chytrid pathogen to flourish and weakened the toad’s defenses.

The new study finds that Monteverde was the driest it’s been in a hundred years following the 1986-1987 El Nino, but that those dry conditions were still within the range of normal climate variability.

“There’s no comfort in knowing that the golden toad’s extinction was the result of El Nino and an introduced pathogen, because climate change will no doubt play a role in future extinctions,” said study lead author Kevin Anchukaitis, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. (ANI)

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