A new study by a team of scientists specializing in zoology and animal health reported, “analyses found no evidence to support the hypothesis that climate change has been driving outbreaks of amphibian chytridiomycosis.”
The study was published in the peer-reviewed PLoS Biology, a journal of the Public Library of Science:
Riding the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian Declines
Karen R. Lips1*, Jay Diffendorfer2, Joseph R. Mendelson III3, Michael W. Sears1
1 Department of Zoology, Southern Illinois University, Carbondale, Illinois, United States of America, 2 Illinois Natural History Survey, Champaign, Illinois, United States of America, 3 Zoo Atlanta, Atlanta, Georgia, United States of America
We review the evidence for the role of climate change in triggering disease outbreaks of chytridiomycosis, an emerging infectious disease of amphibians. Both climatic anomalies and disease-related extirpations are recent phenomena, and effects of both are especially noticeable at high elevations in tropical areas, making it difficult to determine whether they are operating separately or synergistically. We compiled reports of amphibian declines from Lower Central America and Andean South America to create maps and statistical models to test our hypothesis of spatiotemporal spread of the pathogen Batrachochytrium dendrobatidis (Bd), and to update the elevational patterns of decline in frogs belonging to the genus Atelopus. We evaluated claims of climate change influencing the spread of Bd by including error into estimates of the relationship between air temperature and last year observed. Available data support the hypothesis of multiple introductions of this invasive pathogen into South America and subsequent spread along the primary Andean cordilleras. Additional analyses found no evidence to support the hypothesis that climate change has been driving outbreaks of amphibian chytridiomycosis, as has been posited in the climate-linked epidemic hypothesis. Future studies should increase retrospective surveys of museum specimens from throughout the Andes and should study the landscape genetics of Bd to map fine-scale patterns of geographic spread to identify transmission routes and processes.
Author Summary
Once introduced, diseases may spread quickly through new areas, infecting naive host populations, such as has been documented in Ebola virus in African primates or rabies in North American mammals. What drives the spread of the pathogenic fungus Batrachochytrium dendrobatidis (Bd), which causes chytridiomycosis, is of particular concern because it has contributed to the global decline of amphibians. We modeled the spatiotemporal pattern of the loss of upland amphibian populations in Central and South America as a proxy for the arrival of Bd and found that amphibian declines in Central and South America are best explained by Bd spreading through upland populations; we identified four separate introductions of Bd into South America. Climate change seriously threatens biodiversity and influences endemic host–pathogen systems, but we found no evidence that climate change has been driving outbreaks of chytridiomycosis, as has been posited in the climate-linked epidemic hypothesis. Our findings further strengthen the spreading-pathogen hypothesis proposed for Central America, and identify new evidence for similar patterns of decline in South American amphibians. Our results will inform management and research efforts related to Bd and other invasive species, as effective conservation actions depend on correctly identifying essential threats to biodiversity, and possible synergistic interactions.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
I must admit, of all the putative extinctions, I find the decimation of amphibians is most alarming.
Good to know at least some working on the issue are reliable.
I’d like to see some more work coming from this before coming to any definitive conclusion. Australian researchers have about 6 recently extinct species to work on, and a host of extant ones which are in a bad way. I must say, any work that can find out more about chytridiomycosis is a great thing.
“Climate change seriously threatens biodiversity and influences endemic host–pathogen systems”
Yes SJT, that was an interesting point made by the authors!
The big green tree frog, one of the worst affected, was in huge numbers over a vast area of the country with a broad temperature range.
I used to sell bucket fulls, as a kid to UQ for fourpence each for vivisection and it was easy money.
It’s hard to see how a small increase in average temperature alone would be responsible.
It’s a pity the cane toad doesn’t get chytridio.
“It’s hard to see how a small increase in average temperature alone would be responsible.”
That’s why science is hard, it’s pretty well all about things that are hard to see. That’s we have scientists and the scientific method, to research those things that aren’t obvious.
SJT,
The green tree frog lived successfully in areas with a temp range probably in excess of 40c.
They disappeared during a period when temps increased 0.5c and you’re suggesting this is maybe what killed them in all areas?
That’s not what I call science.
“They disappeared during a period when temps increased 0.5c and you’re suggesting this is maybe what killed them in all areas?
That’s not what I call science.”
Your reasoning is not science, that’s for sure. As I said, it’s about the non-obvious, most of the time.
A temperature increase of 0.5C is an average increase of 0.5C. What does that represent to a frog, though? What new peaks were hit, what changes in rainfall happened, what new species suddenly gained an advantage?
Cane toads do ‘get’ chytridiomycosis. It’s helping to knock them off in their native habitats.
Back in the early days of my postgraduate study I used cane toad skin in chytrid lab cultures, although the fungus grows perfectly well in completely artificial substrates. The toads can certainly ‘catch’ it, as can their tadpoles.
Their success in Australia, in spite of chytridiomycosis, is more a reflection on the overall absence in Australia of the toad’s native diseases and predators; as well as the lack of adaptation of native Australian predators, competitors and prey to the toad.
The issue of temperature and chytridiomycosis is more complex than just the temperature envelope in which a frog species is comfortable. The temperature envelope for the fungus comes into play too, and may certainly change a species’ response to the chytrid organism. And of course other cofactors need to be considered as well.
Any response by native frogs may be either positive or negative, although at the present time there is such a complex mix of factors involved in the frog decline phenomenon that it is not possible to make definitive generalisations.
Finally, I think though that it’s a bit of a strawman to link (and then unlink) chytrid-based frog decline to AGW. The drivers for chytridiomycosis are well recognised, and no herpetologist ever blamed AGW for causing frogs to fall off their perches when chytrid was introduced to naive species. There was (and still is, justifiably) concern that AGW might exacerbate chytridiomycosis, but not that it ever drove it.
One might as well have said that harpooning of whales was not driven by climate change.
>One might as well have said that harpooning of whales was not driven by climate change.
What? And I thought it was driven by hot heads and cold hearts…
My understanding from a paper a few years ago is that changes in humidity and temperature(cloud cover), possibly driven by climate change, can exacerbate chytridiomycosis.
Thanks for that Bernard J.
I certainly dont know anything about chitridio but wrt the cane toad I assumed the worst.
There were huge populations of green tree frogs in areas like Roma, SWQ which had very low average RH as well as in coastal areas with very high RH.
This may have affected the fungi performance but the possible tiny extra temp increase would not affect an animal that had survived previous warm periods.
Hi Spangled Drongo,
” I used to sell bucket fulls, as a kid to UQ for fourpence each for vivisection and it was easy money.”
When I studied in Med School , we used endangered tree frogs from Germany for experiments in physiology. IT WAS DISGUSTING !!!
So in animal experiments , as well in our society , there are low status animals and high status animals( whales).
I read from a Norwegian study that 98 % of all animal experiments in Norway are carried out on fish.
Hi Spangled Drongo,
” I used to sell bucket fulls, as a kid to UQ for fourpence each for vivisection and it was easy money.”
When I studied in Med School , we used endangered leav or tree frogs from Germany for experiments in physiology. IT WAS DISGUSTING !!!
So in animal experiments , as well in our society , there are low status animals and high status animals( whales).
I read from a Norwegian study that 98 % of all animal experiments in Norway are carried out on fish.
Hi Ann,
I hope you anaesthetised those frogs first!
I used to muels sheep also as a teenager and hated that and even extracted lambs testicles with my teeth [1200 before breakfast, I kid you not] but these things had to be done.
Sheep with their rear ends eaten out by maggots are not a pretty sight.
It’s not a perfect world and it’s possibly getting less perfecter by the day.
Ann,
It seems that animal rights groups are blaming the vivisection frog trade, particularly out of Africa where chytridiomycocis is endemic for the spread into native populations.
It’s an argument that has logic.
” I hope you anaesthetised those frogs first!” – SD
Hi again SD,
Sure we did , with ether, and then we pinned them down with needles and cut them up , to investigate reflexes and the nervous system with electric probes.
Well, well ,still they twitched , tough days !
Thanks for the info re the frog trade.
OK, I’ll bite; SD, why did you have to extract them with your teeth?
I was young and silly enough to do what I was told and I was probably the only one that didn’t have false teeth.
But it was good training for all-in wrestling.
Those were some of the good jobs compared to diving into a deildrin sheep dip to clear a blocked sump valve or shearing 200 dead and rotting sheep.
“It seems that animal rights groups are blaming the vivisection frog trade, particularly out of Africa where chytridiomycocis is endemic for the spread into native populations.
It’s an argument that has logic.”
To this theory I suspect that we can add the pet trade in axlotols; and quite possibly even fish, which have keratin in their skins, even though they do not manifest chytridiomycosis.
In Australia the banana trade is responsible for moving chytrid around too. Some, if not all, of the spread of chytrid in Tasmania appears to be due to well-meaning folk releasing frogs brought in on bunches of bananas from warmer parts of Australia.
Quarantine in general is still a process that is in its infancy. Australia has some of the most stringent quarantine protocols in the world in place, but it’s really a case of ‘the weakest link’, as the horse flu’ breakout so spectacularly showed last year.
It’s a matter of known unknowns and unknown unknowns. Unfortunately politics and economics creep in to the front end of the process, and even though the political and economic costs are usually greater after quarantine has been breeched, than they would have been to prevent breeches in the first place, we don’t appreciate this as a society until the horse has bolted – or sneezed, as the case may be…
But now we’re treading into free trade territory, and that’s a subject for another thread.