 is one of many amphibian species that have been devastated by the chytrid fungus, but scientists are still debating what role, if any, climate has played.)
FROG GONE: The Panamanian golden frog (Atelopus zeteki) is one of many amphibian species that have been devastated by the chytrid fungus, but scientists are still debating what role, if any, climate has played.
Image: DPAPE/FLICKR
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This much is clear: frogs are dying.
One third of the world's 6,260 amphibian species are globally threatened or extinct. The primary threat to their survival is still habitat destruction, which impacts 61 percent of known amphibian species. But climate change and the deadly chytrid fungus could potentially take the lead over the next century—or at least make things much, much worse for frogs, salamanders and their legless, subterranean cousins known as caecilians.
How much worse? It depends, in part, on whether climate change has the potential to spur—or slow—the growth of the chytrid fungus, which probably originated in South Africa and spread in the 1930s as clawed frogs were exported for frog-based pregnancy tests. Although more than 200 species have been diagnosed with the pathogen, 1,034 have been deemed "susceptible," according to the International Union for Conservation of Nature and Natural Resources (IUCN). And that's where things get tricky.
Some scientists, like Alan Pounds of the Tropical Science Center's Monteverde Cloud Forest Reserve in Costa Rica, believe that warming temperatures have single-handedly triggered the spread of the fungus. Others, like Karen Lips of the University of Maryland (U.M.), College Park, say that climate has played practically no part in its expansion. Still others, like Ross Alford at James Cook University in Australia, contend that hot, dry weather is directly driving most extinctions, and the fungus has had only a tangential role.
In 2008 disease ecologist Jason Rohr of the University of South Florida in Tampa, published a paper saying, in effect, that none of the amphibian extinction theories were quite right—and the parts that were correct were correct for the wrong reasons. To illustrate his point, he showed that frog extinctions were more closely correlated to beer and banana production than to air temperature.
Last week, Rohr traveled to the Ecological Society of America conference in Albuquerque, and presented results from a new analysis and a laboratory study that he hopes will bring the bickering scientists closer to a resolution—his resolution, that is.
First, he took a close look at the timeline of extinctions in Atelopus, the New World frog genus hardest hit by the chytrid: 71 of the 113 species are now presumed extinct. The extinctions have clearly been spreading geographically since 1979, but there's a great deal of year-to-year variation in their numbers.
In the early 1990s, for instance, about 8 percent of Atelopus species were winking out each year. But a closer look shows that just under 3 percent of Atelopus extinctions happened in 1991, whereas 18 percent occur the following year. These peaks and troughs correlate with the El Niño climate cycle, which creates warmer, wetter summers in Central and South America every three to eight years, due to shifts in trade winds and ocean currents. Rohr contends that the frog extinctions occur during cool swings in the midst of warm El Niño years, a hypothesis that goes against Pounds's theory that the fungus grows best at warmer temperatures.
To parse out this complex phenomenon, Rohr and his colleagues decided to bring the frogs and the fungus into the lab. Cuban tree frogs were raised in Styrofoam tanks at either 15 or 25 degrees C for four weeks and then were infected with chytrid fungus. The fungus grew better and killed more frogs at the cooler temperature.
More importantly, Rohr looked at how climate fluctuations would affect the frogs' ability to fight the fungus. If frogs were suddenly moved from the hot temperature to the cooler temperature, they ended up with 25 percent more fungus than if they were kept at the cooler temperature. Rohr suspects that the frogs' ability to secrete fungus-fighting skin secretions is temperature-sensitive.
The bottom line, he explained, is that climate change does matter for the fungus—but probably not as much, or as little, as some would like. Although El Niño events have become more frequent and intense in recent years, scientists are still undecided about their connection to climate change. "Temperature variability has increased in the region," Rohr said, "but I don't think climate is going to account for nearly as much variation as epidemic spread."
Amphibian experts say the new results seem promising. "On a month scale, temperature fluctuations could have strong effects on the immune system," explains immunologist Jacques Robert at the University of Rochester School of Medicine and Dentistry. "When you start to change temperature, going up or down, there is some suppression in the animals."
And chytrid expert Joyce Longcore of the University of Maine, Orono, also agrees that the theory seems reasonable. "I'm primarily on the side of not needing to have climate change to have these infections," she says. "That doesn't mean that in some instances it doesn't slow its spread or make it worse."
Of course, it is still too early to know whether the rest of the amphibian decline community will embrace—or dispute—the new results. Although U.M.'s Karen Lips saw Rohr present the new data, she declined to comment until she sees a paper in print.
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12 Comments
Add CommentIt is there something correlated to we humanlity?
Reply | Report Abuse | Link to thisI mean, people in the world now is simply a part of the evolution of the world of the nature.
What do you think?
My personal view is that people, and all life forms for that matter are merely catalysts in the everlasting process of entropy; the universe is running down and and all living things merely speed the process along.
Reply | Report Abuse | Link to this@stjabc: so, what you're saying is, that despite our having evolved significant cognitive abilities, our base natures are all that matters and because we're here we don't need to think about what we do, we can just do it? That because we exist, and don't normally try to think about our actions, that we shouldn't? Sounds like a plan.
Reply | Report Abuse | Link to this@Shoshin: a completely inane idea that uses a whole bunch of words completely wrong to land at a statement that makes no sense.
Spoonman:
Reply | Report Abuse | Link to thisExplain to me why it is wrong? Please explain how entropy is slowed by life and I'll retract my statement.
"Frogs eat the spatulas in my toaster on Mars next Thursday"...explain to me why that's wrong. Explain to you how it's wrong? I don't even know what it's supposed to MEAN!
Reply | Report Abuse | Link to thisOkay...how is the universe "running down" per se? Assuming you have some answer that even can begin to make sense, you then need to explain how "life" (whatever that means in this context) changes that across the universe in a positive or negative fashion.
Entropy is the increasing of randonmess in nature, reflected in one way by the conversion and use of energy. Life depends on the use of stored energy, and it acts to catalyze this energy and thereby promote entropy.
Reply | Report Abuse | Link to thisTake for example a coal seam. The sun's energy was trapped at a high level by the photosynthesis of the plants that grew hundreds of millions of years ago. The trapped energy lies in wait for erosion for millions or even billions of years to expose, weather and oxidize the coal, moving to a lower energy state. Or people can strip mine it tomorrow and convert the trapped energy into fuel to grow food or make socks. Whichever path is followed, the result is the same, but life forms do it faster.
Too bad about the frogs eating the spatula thing. You should have that looked at.
I know nothing about metaphysics. I think that a lot of people would like to blame evil-doing corporations and man's inhumanity towards man and everything else as possible causal factors, (and that may be true for the most part), but the fact is that the fungus was originally spread by the use of clawed frogs for medical purposes. Who knew? It is just so complicated. What intrigues me is the hinted at correlation of beer and banana production and extinctions. I mean, WTF? right?
Reply | Report Abuse | Link to thisstjabc :
Reply | Report Abuse | Link to thisIts everything to do with us no exceptions.
We destroyed habitat.
We moved species from one region to another.
Our massive population consumes most of the energy (food) available on this planet.
Our species decimated vegetation, the principle converter of solar energy and CO2 to sugars, reducing the production of sugars (basic food) by about 25%.
Biodiversity has disappeared, we can not survive without it.
Shoshin:
Reply | Report Abuse | Link to thisEntropy increases, nothing we can do about that, it a law of nature. Eventually our universe will die, but our planet and sun will die long before that happens.
Its not about the long term, we shall be extinct in the long term. However would you not like to prolong the existence of our species for a while longer, just to know more about why things are. We are in the midst of the sixth extinction started about 5000 years ago when we invented agriculture and started creating deserts.
We shall be dead but I would hope for are species to survive long enough to answer the all important question. I would also love to know if Higgs boson exists.
Not sure where the quote attributed to me came from but it is not anything I said recently (i.e. since about 2000). If I had been asked recently, I would have said that evidence is good that the fungus is moving around, and that it has been the proximate cause of many amphibian dieoffs. I would also have pointed out that there is very good evidence that whether it kills amphibians or not is affected by climate, for example in Australia where above a pretty clear elevational cutoff it has caused extinctions and below that it has become just another endemic disease. In combination, these facts say that present climates affect the virulence of the disease, and that if these change, or have recently changed, the virulence of the disease should respond. Ross Alford.
Reply | Report Abuse | Link to thisScientific earthling:
Reply | Report Abuse | Link to thisQuite the regrets that you have about civilization. Must be tough hauling all that guilt around. Why don't you put it down, relax, and accept the fact that the world is not going to end, climate change is a fact of life on a changing and vibrant planet and that people have nothing to do with it.
If you want to spend your time fighting pollution (I mean real pollution, like pesticides, mercury and toxic waste) or AIDS, hunger, poverty or any of a thousand real worthy causes, I'm there with you. But if you want to waste your time and money bemoaning IPCC defined Anthropogenic Climate Change and looking for loose change in your sofa to buy your next carbon credit from Al Gore, you lost my interest.
NOVA just played (a few days ago) a new 1 hr. program on the global dying off of frogs. Some 10+ yrs. ago I assisted in an amphibian population study within a national park in Pennsylvannia, USA. I can't help but come to the same conclusion now that I did then......it wasn't a mystery then why there weren't a whole lot of salamanders in the creek that was permanently contaminated with asbestos. Similarly, it's not a mystery, to me anyway, that frogs are dying off on a global scale. My connected conclusion: we don't need to understand exactly why we are having a problem such as global frog extinction, ESPECIALLY WHEN IT'S MOSTLY OBVIOUS TO A CASUAL OBSERVER, that the cause is from many things. Habitat loss, water pollution, poor air quality, tendency towards disease due to a variety of stressors, etc..... the list is probably endless but we're not smart enough yet to even come close to knowing. Anyway, the point is: we need to do as much as we can to help in every way we can understand, without wasting efforts on trying to understand situations we mostly understand already ( i.e. we're trashing the planet). If there is a God, we will fix this.
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