Earth Off Balance

Athens Scientists Think Globally and Locally

originally published April 4, 2007

Frogs throughout the world are dying in vast numbers from a virulent chytrid fungus and no one knows what precise factors are contributing to its spread. So says a 2006 article in the journal Frontiers in Ecology & the Environment co-authored by UGA ecologist Scott Connelly. Connelly and other UGA researchers want to know more about the chytrid (pronounced "kitrid") fungus, as well as its effects on our own native frog populations.

Scientists are now playing catch-up to find out why die-offs - such as recent ones in mountainous regions of Central America - are occurring, and whether or not the remaining frog populations in affected areas will be able to recover. Additionally, no one knows what the long-term ecological consequences are when an entire group of animals - in this case, frogs - is removed from an ecosystem.

Flagpole sat down recently with Dr. Whit Gibbons, a UGA Professor of Ecology at the Savannah River Ecology Laboratory, and Connelly, a doctoral candidate studying under Gibbons, to learn more about the multifaceted problem. UGA has received grants from the U.S. National Park Service to look into whether chytrid fungus occurs in the United States, and if so, where.

Gibbons says studies so far show that the chytrid involved in the die-offs in Central America has the same DNA as existing strains, so fortunately, a new and more deadly form is not spreading across the globe. Connelly points out that in every continent with frogs, this fungus is found in native frog populations.

Alarmingly, however, the die-offs in countries such as Panama and Costa Rica are so regular that scientists are now able to track the geographical progression of the fungus and predict where the next animal populations are likely to be affected. “The public definitely should care when some disease spreads and is seriously affecting animals or plants. Epidemics such as this one impact humans either indirectly or directly. It’s disquieting when an unexplained epidemic is affecting our native species,” Gibbons says.

Gibbons appreciates the work scientists at UGA, such as Connelly and others, are doing on the problem internationally. He adds that there is some good news, at least in his own area of study, the southeastern United States. “So far, we haven’t observed an impact on the animals in the Southeast, where this fungus has been found,” he says. He gives the example of native Southern Leopard Frogs, which have been found to have chytrid, but are not dying from it. “Still,” he says, “this is a good reason why continued research is so important. There may be a ‘cascading effect’ if a whole part of a system, which has developed over time, suddenly disappears.”

Connelly agrees. As a stream ecologist, he investigates how ecosystems change with the loss of so many - in some places, entire populations - of the native frogs which are a valuable energy link between stream life and terrestrial life.

“In Panama, we are researching the changes at each site. These die-offs occur in the higher altitudes of the tropics. We’re finding that about 80 percent of all the frogs are gone in two months once chytrid starts spreading there. So far, none of these populations have recovered,” he says. Connelly adds that this is not a gradual selection process in which some frogs survive and re-establish the population with resistant offspring. Instead, this is a sudden and catastrophic decline of an entire group. It’s actually like losing two groups of animals, since the larval stages of many frogs live only in an aquatic habitat. The fungus first attacks and deforms the tadpole’s mouth, but somehow the tadpole survives chytrid while in this aquatic stage. Then, as the tadpole develops into a frog, the fungus does its lethal damage at this terrestrial stage. “When an adult frog is afflicted with chytrid,” he explains, “you see a strange sloughing off of the skin; you can tell the frog is dying.”

Gibbons is concerned about a broader environmental problem: A number of serious diseases are spreading in populations of other animals, such as viruses and infections in birds, sea turtles and mammals. He emphasizes the importance of the “bigger environmental picture” in relation to this overall pattern occurring throughout the world. “Maybe all of these diseases are related to global habitat deterioration,” he says. “It is as if the Earth is losing its immune system.”

Connelly points out that studies show that as frogs decline in an area, the predators dependent upon them also decline. Snakes, birds and other predators cannot survive losing this important food source. He adds: “What is frustrating in particular is that we are lacking the most basic answers in solving global problems like the spread of chytrid. Global ecosystems are changing before we even know what the long-term effects are. These systems are changing so fast that it’s difficult even to record the changes. When these animals are gone, in some places, they are gone for good.”

Liz Conroy

mikeliz@mybluelight.com