climate change


Scientists have unravelled the mechanism by which the fungal disease chytridiomycosis kills its victims.

The BBC reports that a group of scientists has published an article in the journal Science that chytrid fungus kills by changing the electrolyte balance of animals, resulting in cardiac arrest. Chytrid, which was discovered in 1998, is one of the major killers of amphibians across the globe, along with habitat destruction and climate change. Curing amphibians in captivity can now be done using antifungal chemicals, but there is currently no way of treating the disease in wild populations.

If scientists can now discover more about how the elctrolyte balance is disrupted, they may also ultimately, discover a way to reduce the mortality rate in wild amphibian populations.

Six years ago, promises were made by governments from around the world involving the mass extinctions facing so many animal classes, chief among them the amphibian class. The governments vowed to halt the decline in biodiversity by 2o1o. Well, the International Union for Conservation of Nature (IUCN) just issued a report that says, in essence, “let’s not kid ourselves, when next year comes around, it’s going to be bleak.”

IUCN, which puts out the Red List of most endangered species, has produced a 150-page report that details the loss of biodiversity earth has experienced over the last 5 years. “Biodiversity continues to decline and next year no one will dispute that,” said the report’s senior editor. “It’s happening everywhere.”

Here’s a link to story I just read about this.  (Click HERE.)

An excerpt from the IUCN Web site:

The report shows nearly one third of amphibians, more than one in eight birds and nearly a quarter of mammals are threatened with extinction. For some plant groups, such as conifers and cycads, the situation is even more serious, with 28 percent and 52 percent threatened respectively. For all these groups, habitat destruction, through agriculture, logging and development, is the main threat and occurs worldwide.

In the case of amphibians, the fungal disease chytridiomycosis is seriously affecting an increasing number of species, complicating conservation efforts. For birds, the highest number of threatened species is found in Brazil and Indonesia, but the highest proportion of threatened or extinct birds is found on oceanic islands. Invasive species and hunting are the main threats. For mammals, unsustainable hunting is the greatest threat after habitat loss. This is having a major impact in Asia, where deforestation is also occurring at a very rapid rate.

Among endangered species of amphibians, “75 percent are susceptible to climate change while 41 percent of non-threatened species are susceptible as well.” (From study by the International Union for Conservation of Nature (IUCN) as reported in The Economic Times of India.)

You’ve heard the saying, adapt or die. How about adapt and die? Reading a new scientific report by David B. Wake and Vance T. Vredenburg, on the mass extinction that Amphibian Ark aims to avert, a new thought surfaces: Amphibians outlived the dinosaurs because of their adaptability — hey, they’re the Transformers of the animal world — yet the sensitive biomechanisms that make adaptability possible also put them at the greatest risk from new dangers created by man. Hence, their suffering today represents a canary in the coal mine warning us that the planet is in trouble. I recommend reading the full story from the National Academy of Sciences (of USA), but I pasted an excerpt below. And, the Los Angeles Times published a piece on it.

Why this should be has perplexed amphibian specialists. A large number of factors have been implicated, including most prominently habitat destruction and epidemics of infectious disease (19); global warming also has been invoked as a contributing factor (20). What makes the amphibian case so compelling is the fact that amphibians are long-term survivors that have persisted through the last four mass extinctions. Paradoxically, although amphibians have proven themselves to be survivors in the past, there are reasons for thinking that they might be vulnerable to current environmental challenges and, hence, serve as multipurpose sentinels of environmental health. The typical life cycle of a frog involves aquatic development of eggs and larvae and terrestrial activity as adults, thus exposing them to a wide range of environments. Frog larvae are typically herbivores, whereas adults are carnivores, thus exposing them to a wide diversity of food, predators, and parasites. Amphibians have moist skin, and cutaneous respiration is more important than respiration by lungs. The moist, well vascularized skin places them in intimate contact with their environment. One might expect them to be vulnerable to changes in water or air quality resulting from diverse pollutants. Amphibians are thermal-conformers, thus making them sensitive to environmental temperature changes, which may be especially important for tropical montane (e.g., cloud forest) species that have experienced little temperature variation. Such species may have little acclimation ability in rapidly changing thermal regimes. 

 
 

 

Last Tuesday’s New York Times featured a short article about a scholarly frog debate: is the spread of chytrid fungus being fueled by global warming? New and old studies draw differing conclusions. It should be noted that the scientists involved actually aren’t arguing — they’re simply pointing to scientifically valid reports that point to different reasons for the spread of chytrid. But I got a chuckle from a “tie breaking” quote from an Australian biologist:

Ross A. Alford, a tropical biologist at James Cook University in Townsville, Australia, said such scientific tussles, while important, could be a distraction, particularly when considering the uncertain risks attending global warming.

“Arguing about whether we can or cannot already see the effects,” he said, “is like sitting in a house soaked in gasoline, having just dropped a lit match, and arguing about whether we can actually see the flames yet, while waiting to see if maybe it might go out on its own.”

“Monteverde is an ark — and it’s in trouble.” Yesterday on NPR’s “All Things Considered”, there was a 6-minute story explaining how “climate change is shuffling the deck” in Monteverde’s rich biodiversity, starting with the disappearance of the golden toad 19 years ago.  Excerpt:

When nature guide Javier Perez began giving tours of the Cloud Forest preserve three years ago, they would normally spot 40 frogs on their loop walk.

‘Today, only three years later, in a two-hour walk (we see) only two or three frogs…’ (quote from Perez).

“They are indicating to us that there is a problem, and if we don’t take care of the problem, it’s going to move up to our level.”  That’s what an amphibian zoo keeper said Monday in a very informative, nearly hour long radio interview about the amphibian crisis on WCPN radio in Cleveland. I typed below a few excerpts from the interview with husband and wife amphibian experts Kathy Krynak, who manages the amphibian exhibit at Cleveland Metroparks Zoo, and Tim Krynak, naturalist with Cleveland Metroparks: 

“One of the biggest (contributors to the mass extinction) is habitat loss (but) within the last ten years we have a new disease that’s entered the arena — that’s the chytrid fungus. It lives on amphibian skin, and amphibians basically breathe through their skin — and once this happens, they suffocate to death.” – Tim Krynak

Climate change is actually the biggest factor across the board globally in the amphibian declines, so anything that you can do to be a little greener, like Kermit says, in your own lives will help amphibians and the planet in general.” – Kathy Krynak

“Amphibians that live in mountain regions and particularly the humid tropics are having a really hard time because as you increase the elevation, climate change is much more dramatic there. The nighttime temperatures in the areas where chytrid thrives are getting warmer so its 24 hours a day of a chytrid hotbed in the humid tropics.” – Kathy

“They are the cold and slimy canaries in the coal mine. Since they have such sensitive skins and they breathe and they drink right through their skins, changes in their environment affect them very quickly.  They are our best vertebrate bio indicators species so they are indicating to us that there is a problem and, if we don’t take care of the problem, it’s going to move up to our level.”

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