Salamanders can be a proxyindicator for climate change. Changes in salamanders have been linked to climate changes during ancient times, and in a very recent study, salamanders in the US Appalachians seem to have changed in relation to anthropogenic global warming. In fact, the changes observed in these Appalachian salamanders is quite large, very rapid, and thus, alarming. I’m going to describe this study in some detail, and as a bonus for sticking with me on this, I’ll throw in some entertaining Climate Science Denialism near the end. As an additional bonus prize, you’ll get a nice new shiny Internet Meme to print out and attach to your refrigerator.

Salamanders (Order Caudata) are ectothermic, meaning that they get most of their heat from the environment in which they live. There are over 650 species of them and for the most part they are temperate, with none living in Africa and not too many species in Central or South America. The greatest diversity is in the United States. They are opportunistic predators.

Salamanders are diverse in their life histories and behavior. There are species that live all their time in water, and some that spend some of their life cycle in water and some on land, and some that actually never live in the water. Of the former some only shift to land living under certain conditions. Most salamanders are small, but there is an American species that grows to about 75 cm and a Chinese salamander that is abut 1.8 meters long and eats Pandas. OK, I’m only kidding about it eating Pandas. But it is that big. And, of course, people of the region eat them so they are nearly extinct.

There is a paper just out, “Widespread rapid reductions in body size of adult salamanders in response to climate change,” by Nicholas Caruso, Michael Sears, Dean Adams, and Karen Lips, that looks at 20th century changes in body size of 15 species of Plethodon salamanders from the 1950s to the present. This study has a lot of very interesting features (other than the findings). First, it incorporates a huge collection of data (and salamanders) made by a now emeritus researcher, Richard Highton, who had an interest in the beasts and collected piles of information on them. I love it when these old collections are a) usable and b) used. In this case, only a small percentage of the 140,000 salamanders Highton collected (that we know of) were part of the study.

(I would like to pause for a moment and say that I feel much better now. When I was a kid, my friend Kirk and I would collect salamanders and put them in a bait bucket, and put the bait bucket under the cabin. In these hot and dry conditions up in the Adirondack park in August, the salamanders would mummify and become tiny toys we would play with. Until I read this paper I felt partly responsible for the decline of the salamanders. Now, I realize that our small contribution to this was, well, small. But I digress….)

Second, the huge amount of data collected by Highton was supplemented by additional data. This helps anchor the data to current conditions and methods, and, frankly, it probably helps anchor the researchers to the old data as well.

Third, and I think this is the most important part, the researchers did not simply observe changes in key variables over time but they developed a sophisticated model of the biology underlying the data. Here’s the thing. If you observe change in some variable across time, space, or conditions you can speculate about the process underlying the change. But unless you have a sensible biological model to explain (and in some cases develop) the links, you’ve got bupkis. Here, the researchers looked at several possible underlying causal variables and were able to narrow down the list of suspects to two, which, in turn, are affected by climate change (and vary across elevation as well, which is nice because prior studies have shown elevation to be a key factor in recent changes in salamander biogeography).

This study looked at salamanders in West Virginia, Virginia, North Carolina, and Tennessee. The source of the samples is complex and involved multiple sampling efforts combining, as mentioned, the old samples taken by Highton and newer samples. I’ll let you read the original paper if you really want all those details. The key measurement of the salamanders was the SVL, which as you know means Snout-Vent-Length. Also recorded were temperature, humidity, elevation, and all sorts of other variables about the study sites.

Here is the key result in pictures:

Shifting size distributions over time for Plethodon cheoah (a), P. cinerus (b), P. cylindraceus (c), P. jordani (d), P. ventralis (e), and P. yonahlossee (f). The number of sites sampled in each decade is represented by the number in parentheses above the sample size of animals measured for that time period.

Shifting size distributions over time for Plethodon cheoah (a), P. cinerus (b), P. cylindraceus (c), P. jordani (d), P. ventralis (e), and P. yonahlossee (f). The number of sites sampled in each decade is represented by the number in parentheses above the sample size of animals measured for that time period.

As you can see, salamander length goes down over time. Each plot (the stats were all done in R) shows a different species over time, and generally the length goes down. Massive statistical analyses on these data, looking for underlying variables, resulted in this cool little graph showing that warmer-drier conditions were primarily responsible for the changes.

(a) Grand mean changes in standardized difference in mean body size per generation, relative to within-population standard deviation for populations in areas that have become colder and wetter (blue), warmer and drier (red), and either colder and drier or warmer and wetter (khaki). To compare among species and populations with different generation times, we converted body size change into Haldane Ratios. The greatest body size reductions, as indicated by Haldane Ratios, were found in populations that experienced both an increase in temperature and a decrease in precipitation (95% CRI = 0.732, 6.837). (b) Spatial distribution of actual climate trends during the study period; areas with the darkest reds experienced the greatest amount of both warming and drying, blue colors are areas that have become both colder and wetter.

(a) Grand mean changes in standardized difference in mean body size per generation, relative to within-population standard deviation for populations in areas that have become colder and wetter (blue), warmer and drier (red), and either colder and drier or warmer and wetter (khaki). To compare among species and populations with different generation times, we converted body size change into Haldane Ratios. The greatest body size reductions, as indicated by Haldane Ratios, were found in populations that experienced both an increase in temperature and a decrease in precipitation (95% CRI = 0.732, 6.837). (b) Spatial distribution of actual climate trends during the study period; areas with the darkest reds experienced the greatest amount of both warming and drying, blue colors are areas that have become both colder and wetter.

The aforementioned statistical model helps explain how and why the changes occur. It actually turns out to be very simple. As ectomorphs, salamanders get more active when it is warmer. Heat them up and their metabolic rate goes up, so they burn more energy. As you know, life is all about the partitioning of energy into three major categories: Reproduction, maintenance, and growth. The increased metabolic rate cuts into the maintenance part of that system, so the others may be reduced. I’d like to know if reproduction is diminished, but clearly, growth is affected. The science behind the following graph is complex (again, read the original if you want to bask in the formulae) but the meaning is pretty clear.

Results of modeling annual activity (upper row) and annual energy expenditure (bottom row) for a 10 g Plethodon at Catoctin Mountain N.P., MD (FDR), Mountain Lake area, VA (ATW), and Mt. Rogers National Recreation Area, VA (LIM).

Results of modeling annual activity (upper row) and annual energy expenditure (bottom row) for a 10 g Plethodon at Catoctin Mountain N.P., MD (FDR), Mountain Lake area, VA (ATW), and Mt. Rogers National Recreation Area, VA (LIM).

For different regions (where temperature, humidity, elevation, etc may vary) the models incorporating climate change and slamanderness of the salamanders show a modest uptick in activity, or virtually no change, happening along side a significant upward trend in energy expenditure. Temperature matters when it comes to size.

Now here’s the bonus climate science denialism controversy I promised you. Anthony Watts, on his blog Watts Up With That, mentioned this study and then made fun of it. He and his readers derided this excellent piece of science by pointing and laughing at two things. First, the scientists studying the salamanders used OMG COMPUTER MODELS. All climate science denialists know that all computer models are wrong. That is not true of course. Also, the modeling done in the salamander study was different … it was physiological modeling not climate modeling, and it was an excellent piece of work. Essentially, the salamander modeling took reasoning based on long established biology and expanded on it mathematically, then took that and used various techniques to test the mathematical modeling for validity. The second Wattsian complaint about the study is that some other study in the past showed that salamanders GREW, not SHURNK when it got warmer.

And yes, there is in fact a study from a few years ago that looked at fossil salamanders from the last 3,000 years, and showed an increase in body size with warming conditions. But comparing these studies is absurd. This would be like comparing a study of how big lions grow depending on how many antelopes there are from year to year with a different study on the evolution of lions across time as their body size changed. But worse, because these are species living in different regions. So it would be like studying size changes in African lions over decades in Amboseli with long term evolutionary trends in saber tooth cats in Mongolia, and assuming that you are looking at the same thing.

I suppose if one rejects science as does Watts, one would be more comfortable with the creationist idea that there are not really different species of animals, but rather, “kinds” of animals. In this way, one could think of all salamanders as just a “kind.” I suppose.

There are a lot of reasons the studies seem to show opposite patterns. In Yellowstone, that particular species of salamander can get larger if they change from a water based life history strategy to a land based one. In that region warm conditions may increase food supplies in terrestrial areas but not aquatic areas. Water based salamanders can evolve to be larger if their water bases become smaller and shallower, increasing predation and thus selecting for larger body size.

The main difference between the studies is the temporal resolution. The study reported here covers decades of phenotypic change within the range of norm of reaction (i.e., probably not mostly genetic) while the Yellowstone study is over evolutionary time. But there are other differences. Mike Sears, one of the authors of the Appalachian salamander paper, told me this:

Ambystomid salamanders [Yellowstone] require water for reproduction. Some adults live in terrestrial environments, but their larvae all require water. Plethodon salamanders [Appalachian], on the other hand are terrestrial for all life stages. Plethodon salamanders are lungless. They depend on their skin for oxygen exchange, meaning that they are limited to cooler, wetter habitats in terrestrial environments. Because their habitats are predicted to get drier and warmer, this lifestyle imposes some immediate stress (e.g., dry out and you can’t breathe). In fact, if these animals lose too much water over the course of an evening, they retreat from activity.

Most importantly, regardless of the differences between these two species, climate change biologists would not expect all species to respond similarly, within or among species. For instance, ectothermic animals from the Tropics might be expected to be negatively affected by increasing temperatures, whereas temperate species might benefit from them. For that matter, animals with large species ranges might be expected to respond differently to warming climates across their ranges, benefitting some populations while harming others. In fact, for species that are negatively impacted by warming climates, declining body size has been observed and should be expected given basic physiological principles.

Here’s the thing. Anthony Watts and his friends in the Climate Science Denialism gaggle love themselves them cherries. And, this is an example. Using just the titles of articles and not understanding the underlying science behind them, one can pretend to find contradictions that aren’t really there. Also, this is easy to get; it does not take much effort to misconstrue the meanings of a bunch of journal article titles. An active climate science denier can probably do several over a weekend. This expedience then allows the denier to blend the cherries into a nice Gish Gallop. Just look at Anthony Watt’s blog; the cherries flow there like the effluence of a hippopotamus with diarrhea. Who ate a lot of metaphorical cherries.

Anyway, back to the salamanders. There are many cases of well established biologically understood links between climate and physiology. And that is nice because it allows us to observe climate change in the past. But as this article on salamanders (and the Yellowstone paper as well) points out these systems have an important additional implication: Climate change is going to change more than just climate. From the paper:

Regardless of whether the effect is genetic or environmental, the degree of body size reduction we documented in Plethodon was both large and rapid. For the six species displaying significant trends, body size reduced by an average of nearly 8% across the time period examined. When standardized for within-population variation, this corresponds to approximately a 1% body size reduction per generation in these species. This magnitude of change is on par with some of the largest phenotypic changes observed in contemporary populations. Thus, these changes represent some of the fastest responses to environmental perturbations ever recorded and lend support to the observation that phenotypic responses, particularly those related to anthropogenic disturbance, are both more rapid and more extreme than those observed in natural contexts or over longer time periods. The rapidity and the widespread extent of these changes across so many species in a biodiversity hotspot may signal rapid adaptation to novel environmental conditions.

And now, for your patience, your refrigerator magnet:

_____________________________
Photo Credit: Furryscaly via Compfight cc

For another writeup see Climate change makes salamanders shrink, scientists say: A warmer and drier climate is likely causing wild salamanders in North America to shrink, say scientists by Cudeshna Chowdhury.

Caruso, N., Sears, M., Adams, D., and Lips, K. 2014. Widespread rapid reductions in body size of adult salamanders in response to climate change. Global Change Biology. DOI: 10.1111/gcb.12550

Bruzgul J. E., Long W. & Hadly E. A. 2005. Temporal response of the tiger salamander (Ambystoma tigrinum) to 3,000 years of climatic variation. BMC Ecol., 5. 7 (2005).

Comments

  1. #1 Dan Satterfield
    United States
    March 27, 2014

    My all time fave Anthony Watts “fail” was when he insisted that only a fraction of weather stations in the USA were reliable for climate, and that there was no warming. NOAA/NCDC ran the data with his stations only and they showed slightly more warming, but otherwise no significant difference.

  2. #2 Buck Field
    Patagonia
    March 28, 2014

    It is distressing when critics of bad science use arguments just as uninformed and foolish as those they hope to refute.

    “…comparing these studies is absurd.”

    Perhaps it is, but name-calling is no substitute for explaining to your audience WHY such comparisons are properly rejected and showing how this example demonstrates the disqualifying characteristics.

    Asserting ” This would be like comparing [study x] …with a different [study y]” is a hand wave unless we can state a general principle of how to prioritize differences.

    This blog picks out differences which support its preferred conclusions, claiming scientific support for them and accusing opponents of rejecting science…just as Watts (presumably) does.

    While I’ve not read his blog, I highly doubt he boasts that he “rejects science” as claimed above.

  3. #3 daedalus2u
    March 28, 2014

    I suspect the mechanism is O2 delivery. Mostly salamanders get O2 through their skin, if they have a higher metabolic rate per mass. then they need more surface area per mass to support that greater metabolic rate. They have to get smaller.

    There could also be effects mediated through endocrine disruption. Most xenobiotic chemicals that have physiological effects do so by interfering with the normal regulation of physiology. When physiology is interfered with, it becomes less efficient and so requires more calories to do the same things. That usually results in accelerated maturity.

  4. #4 Greg Laden
    March 28, 2014

    Buck: I describe why comparing these studies is absurd and related one of the study’s author’s comments on that exact topic. Maybe those words were somehow deleted from your copy of the blog post.

  5. #5 Ray Del Colle
    March 28, 2014

    “For many species, including humans, the climate may be changing faster than we can keep up.” http://clmtr.lt/c/EWL0cg0cMJ

  6. #6 Marconi Darwin
    March 28, 2014

    So Buck has not read the WUWT blog, and finds that calling an absurd comparison as absurd is uncalled for? Go find a salamander to copulate with, BUCK!

  7. #7 Buck Field
    March 29, 2014

    @Greg,

    You seem to be saying that we’ve provided an explanation by simple assertion of an analogy. If we are to accept as criticism simply claiming an analogy we like (“This would be like comparing [example 1 of my choosing] with [example 2 of my choosing]“) then we can hardly expect to be taken seriously as behaving better than the religious bigots using equally sloppy reasoning. This doesn’t make either side right or wrong, it just doesn’t seem sufficiently stringent to keep out lots of bad reasoning.

    >I describe why comparing these studies is absurd and related one of the study’s author’s comments on that exact topic. Maybe those words were somehow deleted from your copy of the blog post.

    Perhaps they were. The only thing I noticed was a cherry picked lion analogy by way of justification. I propose that the criticism would be much stronger if you were to include something of why that analogy is a good one, based on mistakes one would make if one actually used it.

    Even better: provide a historical analogy of where similar mistakes were made in real science, and how we learned that the errors Watt’s makes so frequently lead to incorrect conclusions.

    Note: this requires actual work – and may not be as fun, and certainly not as immediately gratifying as name calling for those who are into that sort of thing.

  8. #8 Greg Laden
    March 29, 2014

    Buck, a solid scientific explanation by an expert in the field was provided, as well as commentary by me, and paleo proxies are in my field of study as well.

    Also, that required work. I read nine peer reviewed papers as background to catch up on salamanders and had extensive communication with the OPs author.

    What happened here is that you didn’t read my post, complained about part of it, terribly botched your remarks, got called on it and now you are back pedaling.

  9. #9 Buck Field
    March 29, 2014

    >a solid scientific explanation by an expert in the field was provided,
    Of the claim “…comparing these studies is absurd.” ?

    Please cite.

  10. #10 dean
    March 29, 2014

    I’m never sure whether Watts says what he does because he doesn’t understand the work and so doesn’t realize what he says isn’t true, or whether he knows just enough to to know how to craft a lie to fit his position. Whichever it is, he is consistent.

  11. #11 Buck Field
    March 29, 2014

    @Dean,

    Watts mental processes are most certainly the same kind we all use, but proceeding from a different paradigm. It’s just as unlikely he can see problems right in front of his eyes.

    Chinese astronomers who lacked the “perfect and unchanging” model of the heavens were able to record supernovas that Europeans couldn’t see until the late 1500’s. We are constrained by our cognitive frames and motivated reasoning .

    See we all have basically the same brains. Watts seems to do something very similar with science as Greg does with my objection. Rather than address my claim that his presentation of support for his position is lacking, he argues that the position itself is correct.

    If I have a number with 5 non-zero digits to the right of the decimal point, no one here needs to know the value of them to criticize its use in a situation where an integer is called for. Everyone can object by saying “That number is not an integer.” For me to argue the evidence that my number is accurate is like Greg arguing the support for the salamander studies, which I take to be as accurate and reliable as anything.

    When his error is pointed out however, just like the religious, he accuses his critic (here: of “backpedaling”).

    Even if such accusations are without merit, they avoid one being shown in error. It can be just as painful for a good scientist to admit errors as any of the faithful, unfortunately.

    For this reason, I say: Use evidence and convince me I’m wrong. I don’t like being wrong, but I like being faithful to following evidence more. I think it is our willingness to accept criticism and use it to strengthen our mental models that distinguishes good science.

  12. #12 dean
    March 29, 2014

    Buck, read the damn article and try to understand it. The answer to your “objection” is there. Don’t ask someone else to do the work you won’t do.

  13. #13 Buck Field
    March 29, 2014

    @Dean

    I assume by “damn article” you mean “Widespread rapid reductions in body size of adult salamanders in response to climate change,” by Nicholas Caruso, Michael Sears, Dean Adams, and Karen Lips.

    You can’t mean to claim that these biologists explained why Greg’s lion-study analogy illustrates a defect with Watt’s reasoning, surely!

  14. #14 dean
    March 29, 2014

    Read Greg’s post, carefully. If you miss it again you are willfully doing so.

  15. #15 Buck Field
    March 29, 2014

    @Dean,

    Do you now you intend to claim that somewhere in the post selection of the lion analogy with something more substantial than a bald assertion of “absurd” & “This would be like…”?

    Actually, in rereading here, I noted additional errors. For example, suggesting “assuming that you are looking at the same thing”. Granted, I’ve not read Watts, but it seems unlikely he would not draw an analogy (however flawed) to make his misguided points simply to make it sound better and more reasonable. The fact that Watts is wrong doesn’t give us permission to be just as sloppy as the least adept thinkers around.

    Let’s say I wanted to criticize Watts ridicule of the report, I’d point out that he implies the scientists are inconsistent since a past study showed salamander size increased with temperature. Let’s take that as his position. I’d then point out the reasoning is flawed because biological effects like size tend to have optima, illustrated by many common examples. If we increase the temperature starting from 0, humans tend to die less and get more comfortable, but beyond a certain point, they don’t.

    This is significantly and importantly different than simply stating a claim is absurd and then asserting something like: “Watts reasoning would be like saying if we have one foot frozen in a bucket of ice, and the other boiling in water, on the average, we’re comfortable. It’s ridiculous!”

    I hope this clears up the objection.

  16. […] 2014/03/27: GLaden: Alarming Rates Of Climate Change Caused Alarming Change in Salamanders […]

  17. #17 Jung Choi (@jung_gt)
    April 3, 2014

    I don’t know if Buck is trolling here, or is raising a genuine objection from his point of view. I’ll assume the latter. Perhaps Buck is not a biologist, or lacks familiarity with with this kind of biology. What Greg has clearly stated, with an exaplanation by one of the study’s authors, is that the Appalachian salamanders and the Yellowstone salamanders are different genera, with different life histories. Biologists know that one cannot presume that different species living in different habitats would or should respond to environmental changes in the same way. What’s good for the gander is not always good for the goose. Moreover, Greg explains that the Yellowstone study is over evolutionary time scales, whereas the Appalachian study is over decadal time. Such differences, to a biologist, are enough to make comparison of the two studies “absurd.”

  18. #18 Buck Field
    April 4, 2014

    @Jung,

    What Greg stated in terms of its content is not at issue, it is his lack of rational justification. It’s as though we’re discussing pi, and you are arguing for the correctness of the digits Greg provided, with which I agree. I agree with Greg’s position, but object to sloppy, unscientific justification that goes no deeper than name-calling as “absurd” & and drawing an analogy very unlikely to be taken as persuasive by the undecided (& should not be) if rational justification is our guide.

    It certainly seems unlikely to productively reach any of the victims of GCC denialism / religion.

  19. #19 Greg Laden
    April 4, 2014

    Thank you for your concern.

  20. #20 dean
    April 6, 2014

    Thanks for clearing up the point that you had no point Buck. Going from stating there was nothing in the article to support Greg’s point to saying What Greg stated in terms of its content is not at issue” is all the proof we need of your intent.
    The real issue is that, for some reason, you claim to believe that pointing out someone who has a long, demonstrated, documented, history of distorting scientific results is once again distorting results and lying about there being an article that contradicts it is somehow wrong. That’s amazing, especially when
    a) the explanation of why the comment in question from Watt is in the article, and
    b) You admit you’ve not read Watt

    It’s a truly clueless display on your part. Tone trolling is too kind a name for it.

  21. #21 Buck Field
    April 6, 2014

    @Dean,

    I assert that HOW we analyze and criticize is more important than the opinions we hold.

    It is the systemic inability to recognize error that seems to most often lead us astray. Failure to recognize this can make us as bigoted as any jihadist, or Watt/Ham.

    If that’s trolling, we simply disagree.

  22. #22 Greg Laden
    April 6, 2014

    “It is the systemic inability to recognize error that seems to most often lead us astray. Failure to recognize this can make us as bigoted as any jihadist, or Watt/Ham.”

    And this is why we are glad you recognized your error!

  23. #23 dean
    April 6, 2014

    “It is the systemic inability to recognize error that seems to most often lead us astray.”

    What a stupid statement in this setting: Ham, Watt, and their ilk, do not have a “systematic inability to recognize error” — they are habitual (congenital would be more appropriate) liars. They are not missing the point of the research, they are deliberately telling lies.

  24. #24 Buck Field
    April 6, 2014

    I’m not convinced of that these people are telling lies, any more than I think Greg is lying in his responses. I think he (and they) honestly can’t see facts too painful to confront. When someone resorts to snark or insult, they’re excusing themselves from the realm of reason. This is common with religious apologists who are confronted with basic problems inherent in their positions, and it is properly condemned. It doesn’t mean they’re lying, it just means they’ve turned from the road of evidence which seems to be heading in a “wrong” direction.

    Greg seems loathe to admit his argument has serious weaknesses, even though his positions and criticisms are quite valid. Such is a weakness we all share. The ability to overcome this insecurity is what distinguishes good science and, some would say: explains its properly unique epistemic status and progress as the most productive system of thought ever invented.

  25. #25 dean
    April 6, 2014

    I’m not convinced of that these people are telling lies,

    If you’re not convinced you haven’t been paying attention. It isn’t exactly clear what you believe, actually, or what you’re saying.

  26. #26 Buck Field
    April 7, 2014

    The supposition that I haven’t been paying attention is not only reasonable, it’s accurate.

    From random page hits, it seems Greg has been going back and forth with these guys for some time. My assessment is that people lie to others by conviction to a position they believe correct, and naturally set a low threshold for confirming evidence. This is entirely natural, and how our brains are wired. Hence the importance of structures and “rituals” to weed out errors in such an unreliable method. I would be very interested to see a reference to where Ham or Watt actually admit duplicity or that there’s no possibility of a “delusion defense”.

    Our brains evolved for survival & synaptic efficiency, not accuracy in modeling reality. Math, (perhaps our purest science) rests on some pretty dubious foundations, yet mathematicians routinely, explicitly affirm the contrary with religious zeal and regrettably often, become aggressive when counter examples are presented.

  27. […] Alarming Rates Of Climate Change Caused Change in Salamanders [Greg Laden's Blog] […]

Current ye@r *