Study: Global Warming Not Killing Off Arizona Frogs

Arizona researchers say that a fungal disease killing off frogs in the state probably isn't being triggered by global warming.

Two herpetologists and a state Game and Fish Department biologist agree rising temperatures in Arizona aren't acting in the same way as they are in Central and South America, where according to a new study warming is the underlying cause for the disease killing frogs there.

Since 1998, researchers have known that the chytrid fungus is attacking Arizona frogs. They now say it has occurred in 12 Arizona frog species, according to a 2003 Arizona Game and Fish report.

About half these species declined significantly because of the disease, while the disease is probably linked to declines in another one-fourth of the species, said Philip Rosen of the University of Arizona.

But warming is not a likely cause for it in Arizona because its climate is generally hotter than in Central and South America, said Rosen, Cecil Schwalbe of the U.S. Geological Survey, and Michael Sredl of the state Department of Game and Fish.

The Latin American research says global warming has accelerated chytrid disease there by increasing cloud cover that has cooled daytime temperatures and warmed the nights.

The Arizona scientists said global warming could threaten Arizona frog species for other reasons.

If the state's recent warming trend continues to be accompanied by droughts that have occurred most of this decade, springs, washes and streams that are homes for frogs could dry.

That has already occurred in one canyon in Saguaro National Park East, they said. Drying, combined with fires afterward, eliminated a population of lowland leopard frogs early in this decade, Rosen and Schwalbe said.

Researchers said that even if rainfall stays the same, hotter temperatures will mean increased evaporation that also could dry up the frogs' water sources.

"Right now we are in a drought and setting these temperature records. They seem to be hand in hand, although nobody's admitting it," said Schwalbe, an ecologist. "That's why the native frogs are in such trouble. All of these factors acting on the few remaining populations can push them over the edge."