Guest post by Marc Hendrickx
A little over a month ago reports appeared in the press (eg. Butterflies ‘fly early as planet warms’) that the common Brown Butterfly (Heteronympha merope) was emerging 10 days earlier than it was 60 years ago all due to global warming attributed solely to CO2 emissions. The report was based on a paper published in Biology Letters. The article was titled “Early emergence in a butterfly causally linked to anthropogenic warming” by Michael R. Kearney, Natalie J. Briscoe, David J. Karoly, Warren P. Porter, Melanie Norgate and Paul Sunnucks was published online on 17 March 2010. The abstract can be accessed HERE.
The basis of the study was opportunistically collected observational data of butterfly emergence based on museum records and private data collected between 1941 and 2005 in an area centred around Melbourne, Australia, a city of about 4 million people. No links to the original data or location information of observations were provided in the published article.
The authors gauged the temperature dependence of Heteronympha merope under laboratory conditions and used historical weather data for 1945–2007 (Bureau of Meteorology, Australia) from Laverton (37.868 S, 144.768 E), a “rural” site close to Melbourne, to model the physiological response of H. merope to temperature. The authors claim that this weather station is a ‘high-quality’ site, unaffected by changes in exposure, urbanization, instrumentation, etc., during the study period. Weather records (mean monthly maximum and minimum air temperature, wind speed and cloud cover) were translated into microclimates experienced by immature H. merope using biophysical modelling software (NICHE MAPPER, http://www.zoology.wisc.edu/faculty/Por/Por.html#niche).
The observed temperature trends at Laverton were compared to output from extended climate model simulations for the single-model grid box overlying Melbourne and Laverton. Anthropogenic climate forcing included observed increases in greenhouse gases and estimated variations of anthropogenic aerosols, whereas natural external climate forcing included estimated changes in solar irradiance and volcanic aerosols.
The results are summarised in Figure 1 from the paper
I found a number of issues with this paper that pointed to strong confirmation bias and quickly put together a comment that I submitted to Biology Letters on 19 March 2010, just two days after the article was published on line. A copy of the manuscript appears below. I received notification this week that the manuscript was rejected. The reviewer comments make interesting reading (see below) and I thought I would share them with WUWT readers, with a view that the collective brain of WUWT readers would help find the necessary references such that I might be able to re-submit the comment to Biology Letters sometime over the next few weeks. I’d also be interested in hearing the views of the authors and invite them to add their comments.
Comment on Kearney et al., 2010: Early emergence in a butterfly causally linked to anthropogenic warming.
Kearney et al. (2010) examine phenological change in Heteronympha merope (Nymphalidae) to test whether (i) the phenological shift could be explained by air temperature change, and (ii) that the associated change could be attributed to human influences. Kearney et al., contend their results support:
- a shift in the mean emergence date for H. merope of 1.6 days per decade over a 65 year period over 12,000 km2,
- an increase in local air temperature of 0.14ºC over the same period, and
- attribution of the phonological and temperature change to anthropogenic warming, due to greenhouse gas emissions.
There are significant issues with the study outlined below that negate the conclusions:
1. Observed emergence times for H. merope were based on opportunistically collected data over an area of about 12,000 km2 (geographic area-37.60-38.54 Lat, 144.17 to145.48 Long.) centred on the Melbourne CBD. The location of individual observation locations is not provided and there potential for location bias is not discussed. Nor is there a discussion of the potential effect of confounding influences that may affect emergence times. These influences include: human impact on habitat (Kobayashi et al., 2009), pollution, coincidence in emergence of H. merope with changing emergence patterns of its food stock, food availability and variation over time. These factors may have provided adaptive stresses favouring earlier emergence.
2.The methodology for determining thermal dependence of development rate for eggs, larvae and pupae did not account for other variables that might be a factor in emergence such as: atmospheric CO2 content or affect of atmospheric pollutants such as CO, and ozone common in urban environments. There is a considerable body of evidence demonstrating that effects of elevated CO2 on plants can influence insect herbivore performance (Watt et al. 1995, Bezemer and Jones 1998). Changes in leaf chemistry for instance, such as decreased leaf nitrogen and increased carbohydrate and polyphenolic concentrations at elevated CO2 (Cotrufo et al. 1998, Penuelas and Estiarte 1998), might affect insect development (Slansky 1993) and potentially effect emergence timing. These factors were not taken into consideration and as such the link between emergence timing and temperature cannot be conclusively stated.
3.To assess whether the observed change in climate could be attributed to human influence, the observed April-October mean temperature trend for 1944-2007 for the weather station at Laverton (Bureau of Meteorology-BOM ID 87031) was compared to climate model simulations. Laverton is affected by urbanisation effects from significant changes in land use over the period of observations. Australian Bureau of Statistics (ABS 2008, ABS 2008a) data show an increase in population in the area from 7854 in 1933 to 132793 in 2008 (ABS, 2008, 2008a). Hence to define the station as “rural” is a misrepresentation. NASA GISTEMP defines the station as “Urban” with a population of 2.7 million (GISTEMP, 2010). A station at the western edge of the study area with records spanning the period 1903 to 1998 shows no substantial warming (Figure 1). This station, Durdidwarrah BOM ID 87021, is located in the Brisbane Ranges National Park in an area that has not experienced significant land use change since the 1870s when dams were constructed (Catrice, 1997). A comparison between Durdidwarrah, Laverton and the Melbourne CBD station (BOM ID 86071) indicates substantial warming over the Melbourne Region. The disparity between the rural station and the two urban stations suggest this warming is due to urbanization, rather than increases in greenhouse gases. The temperature increases due to urbanization are similar to those reported in China (Jones et al., 2008).
References
ABS 2008. Australian Bureau of Statistics 3105.0.65.001 – Australian Historical Population Statistics. www.abs.gov.au (accessed 18 March 2010).
ABS 2008a. Australian Bureau of Statistics 3218.0 Regional Population Growth, Australia. www.abs.gov.au (accessed 18 March 2010).
Bezemer, T. M., & Jones, T. H. 1998 Plant–insect herbivore interactions in elevated atmospheric CO2: quantitative analyses and guild effects. Oikos 82, 212–222.
Catrice D. 1997 Brisbane Ranges National Park. Parks Victoria. Department of Natural Resources and Environment, Melbourne Victoria (accessed 18 March 2010)
Cotrufo, M. F., Ineson, P. and Scott A. 1998 Elevated CO2 reduces the nitrogen concentration of plant tissues. Global Change Biology 4, 43–54
GISTEMP 2010. NASA GISS Surface Temperature Analysis – Station Data ‘Laverton’ GISTEMP ID 501948650000 (http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=501948650000&data_set=0&num_neighbors=1) (accessed 18 March 2010).
Goverde, M., Erhardt, A., & Niklaus P. A. (2002) In situ development of a satyrid butterfly on calcareous grassland exposed to elevated carbon dioxide. Ecology 83(5), 1399-1411
Jones, P. D., Lister, D. H., and Li Q. (2008), Urbanization effects in large-scale temperature records, with an emphasis on China, J. Geophys. Res., 113, D16122, doi:10.1029/2008JD009916.
Kearney, M. R., Briscoe, N. J., Karoly, D. J., Porter, W. P., Norgate M. and Sunnucks P. 2010 Early emergence in a butterfly causally linked to anthropogenic warming. Biology Letters (doi: 10.1098/rsbl.2010.0053)
Kobayashi, T., Kitahara, M., Suzuki, Y. and Tachikawa, S. 2009. Assessment of the habitat quality of the threatened butterfly, Zizina emelina (Lepidoptera, Lycaenidae) in the agro-ecosystem of Japan and implications for conservation. Transactions of the Lepidopterological Society of Japan 60(1), 25-36.
Penuelas, J., & Estiarte M. 1998 Can elevated CO2 affect secondary metabolism and ecosystem function? Trends in Ecology and Evolution 13, 20–24.
Slansky, F. 1993 Nutritional ecology: the fundamental quest of nutrients. Pages 29–91 in N. E. Stamp and T. M. Casey, editors. Caterpillars: ecological and evolutionary constraints on foraging. Chapman and Hall, New York, New York, USA.
Watt, A. D., Whittaker, J. B. , Docherty, M., Brooks, G., Lindsay, E. and Salt D. T. 1995 The impact of elevated atmospheric CO2 on insect herbivores. Pages 197–217 in R. Harrington and N. E. Stork, editors. Insects in a changing environment. Academic Press, London, UK.
=================================
Rejection Letter received April 20 , 2010. Dear Mr Hendrickx
I am writing to inform you that we have now obtained responses from referees on manuscript RSBL-2010-0263 entitled “Comment on Kearney et al., 2010: Early emergence in a butterfly causally linked to anthropogenic warming.” which you submitted to Biology Letters.
Unfortunately, your manuscript has been rejected following full peer review. Competition for space in Biology Letters is currently very severe, as many more manuscripts are submitted to us than we have space to print. We are therefore only able to publish those that are exceptional and present significant advances of broad interest, and must reject many good manuscripts.
Please find below the comments received from referees concerning your manuscript, not including confidential reports to the Editor. I hope you may find these useful should you wish to submit your manuscript elsewhere.
We are sorry that your manuscript has had an unfavourable outcome, but would like to thank you for offering your work to Biology Letters.
Yours sincerely
Publishing Editor
Editor’s comments:
I am rejecting this in view of the strong criticisms by refs. 1 and 3. If the author can deal with these comments, we could consider this for e-letters.
Reviewer(s)’ Comments to Author:
(MH-I have added comments in italics)
Referee: 1
Comments to the Author(s)
The ms is a critique of a recent publication by Kearney et al in Biology Letters. But I am not convinced by any of the author’s three criticisms of the paper.
The first criticism is that the data presented in Kearney et al does not support evidence of a change in emergence times over the study period. Kearney et al note in their paper that while “the opportunistically collected data probably adds considerable noise to any signal of phenological shift, there is no reason to expect such data to be chronologically biased”. To me, this proviso seems sufficient (MH-this seems difficult to justify as no actual data is presented). For the criticisms in the current ms to be supported, the author should present some evidence that this species or others are shifting their phenology related to some of the other factors suggested, or some evidence that in fact the data does not support a shift in phenology. (MH-Can WUWT readers help out with suggestions?) I also do not know where the author has extracted the “area of 12000 km2” data from (MH-this was based on the geographic coordinates provided in the paper) , or that the data were drawn from “disparate, genetically diverse groups” (MH-This was an assumption I made that there would be significant genetic variation over a large geographic area-the area covered by the study contains a range of geographies and sub-climates that may provide local variation in emergence timing. The absence of location data for observations makes it impossibel to judge the potential affect of geographic bias).
The second criticism is that the physiological model did not account for other possible variables. No, but the fit of observed phenology to that modelled based on climate was extremely close. For this criticism to be justified the author should again present some empirical evidence that the other variables listed influence emergence times in this species or similar species. (MH-Can WUWT readers help out with suggestions?)
I am most concerned about the third criticism levelled by the author, that the temperature increase noted for the meteorological station in the Kearney et al paper is dependent on urbanisation effects. The author here presents data from a rural met station and argues that it has shown no increase in temperature over the same period of time. However, the comparison is not valid, because the regression of temperature against year in Fig 1 for the Durdidwarrah station is run from 1903 to 1998, rather than 1944 to 2007, as in the Kearney et al paper. Examination of the figure shows that had data for the approximate 1940 to 2000 period been analysed for Durdidwarrah, there would have probably been a significant increase in temperature, comparable to that reported for the Laverton station by Kearney et al. In this case it is essential to compare like with like, as the Kearney et al paper is not looking at changes to butterfly phenology since 1903, but from the 1940s. (MH-Durdidwarrah is a good station but suffers from a number of breaks in reporting. The reviewer is correct in arguing that a trend through Durdidwarrah from 1940 through 2000 would yield a decadal trend similar to Laverton, however virtually all this warming occurred in the late 1940s, the trend since 1950 has been flat).
There are a few presentational errors: various spellings of “phenological” and “effect” and “affect”, “Nymphalidae” spelt incorrectly, Fig 1 could be presented more clearly.
Referee: 2
Comments to the Author(s)
In the short intro, the author writes twice “phonological changes”. I guess that would be “phenological changes”? (MH based on this I take it that Ref 2 was generally happy with the manuscript)
Referee: 3
Comments to the Author(s)
The author makes some relevant and potentially relevant points in his comment on Kearney et al., (MH-my bold) but this manuscript does not bring this criticism in a sound way, as it stands. It needs major revision before it may become acceptable for publication.
1) Point 1 – Hendrickx is criticizing the use of opportunistically collected data. Kearny et al have made the assumption that there is no obvious bias in these data. So, here the author should more convincingly show that there is indeed bias that may impact on the conclusions. It is not enough mentioning the opportunistic nature of the data. This point needs more work. (MH-again any references that demonstrate effect of other influences on emergence appreciated)
2) Point 2 –CO2: that may be a valid issue that has not been considered as an alternative (or interaction) effect by Kearney. Another relevant paper would be Mevi-Schultz et al. 2003. behave Ecol Sociobiol 54: 36-43 (MH-this appears to be generally supportive of my point 2).
3) Point 3: I don’t get this point. How can you distinguish between urbanization and an increase in greenhouse gasses per se? What would be the direct and the indirect effects of urbanization for the system considered. Again, the author is not making his point in a clear way (MH-I would have thought the comparison between the three stations clearly demonstrates a UHI effect over the Melbourne region).
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A link to the map of the late cretaceous (not sure of source):
http://www.scotese.com/cretaceo.htm
“The authors claim that this weather station is a ‘high-quality’ site, unaffected by changes in exposure, urbanization, instrumentation, etc., during the study period.”
Wow, Anthony, your surfacestations work continues to have impact. The authors of this Aussie paper at least had to address the quality of the station and the UHI affect, even if they are only paying lipservice.
Seems completely plausible that UHI could be a significant factor in emergence times. IMHO, the critical issue is that this is based on localized anthropogenic warming; whatever your belief about AGW, its proof is clearly outside the scope of this study.
The problem here is proof of anything. One does not prove one falsifies. I think you need to demonstrate the assumed correlations simply do not exist because of the heat island effect that you point out etc. If something is based on an assumption that is inductive logic. The appropriate logic of science is deductive. If something is based on an assumption, something like the assumption of representativeness, one can just a rightly assume non representativeness. This logic then demands the representativeness or non rep. must be demonstrated and properly identified. It would seem to me that the hypotheses that CO2 driven warming is demonstrated by early hatching. It would seem that the increased temperatures over the period is important to that conclusion. The hypothesis that this temperature rise is due only to CO2, has been clearly demonstrated false.
Popper’s theory of demarcation may be articulated as follows: where a ‘basic statement’ is to be understood as a particular observation-report, then we may say that a theory is scientific if and only if it divides the class of basic statements into the following two non-empty sub-classes: (a) the class of all those basic statements with which it is inconsistent, or which it prohibits—this is the class of its potential falsifiers (i.e., those statements which, if true, falsify the whole theory), and (b) the class of those basic statements with which it is consistent, or which it permits (i.e., those statements which, if true, corroborate it, or bear it out).
I also want to remind everyone that models do not produce data only estimations of what we think that data may looks like.
From a pure statistics point oview, looking at the charts there are not enough data points to say anything with classical statistical significance about any of this. The bare minimum for a student’s T distribution (approximating a normal distribution) for statistical significance testing on say a regression analysis, would be 30 data points which would still give a high potential variation due to sample size error alone, even in a relatively loose 90% confidence interval. And, of course, there are the issues of sampling error, equipment error, implied cause and effect, etc. Scatter diagrams such as above have no meaning. This is poor science (no science) and merely another case of the “band wagon effect” with someone looking to get brownie points from the green crowd by piling on to the band wagon.
I want to start with a comment on the title: Early emergence in a butterfly causally linked to anthropogenic warming.
The assumption is the warming is anthropogenic. I’ll wager a Trillion Zimbabwean dollars there is nothing in the body of the report that shows the warming is anthropogenic. It just assumes it is.
“Referee 3, Point 3: I don’t get this point. How can you distinguish between urbanization and an increase in greenhouse gasses per se? What would be the direct and the indirect effects of urbanization for the system considered. Again, the author is not making his point in a clear way (MH-I would have thought the comparison between the three stations clearly demonstrates a UHI effect over the Melbourne region).”
I believe what is meant by this objection is: The UHI effect could in theory result from a greater concentration of CO2, rather than from the presence of concrete, cars, air conditioners, heating furnaces, and from land-use changes. I believe I’ve seen this before in another WUWT post, that some warmists are actually attributing UHI to CO2concentration rather than to these other obvious factors.
What the referee needs is an analysis proving the specific causes of UHI.
Anyway it is not the prerogative of climate change researchers only to be slightly confused but still I believe here is another one who has got things “upside down”
http://www.telegraph.co.uk/science/dinosaurs/7624014/Dinosaurs-died-from-sudden-temperature-drop-not-comet-strike-scientists-claim.html
“The drop in temperature is thought to have occurred because high levels of CO2 were in the atmosphere which caused global temperatures to rise and polar ice to melt – a phenomenon currently predicted for Earth.”
Did he mean this or was he wrongly quoted? Whatever happend surely AGW was not to blame.
Just offhand, I think insects respond to other things far more than they do temperature. Food and water comes first to mind.
And here I though it was the duty of the scientists involved in the research to prove their case, not the other way around. If so, can’t anybody just write up any nutty conclusion and say prove this wrong. Seems like this is what happens with the alarmist hoaxers. Is it a competition just for grant money, and no longer truth?
So there …
Jim G (09:25:38) :
I would spend a little more time studying statistics before proclaiming how many observations are necessary for statistical significance. Thirty data points is not the bare minimum for testing the significance of a slope with the t-distribution: the minimum is three. Yes with only three datapoints, confidence intervals are wide etc, and nobody would take you seriously.
I suspect what you are misremembering, is that with about 30 degrees of freedom, the normal distribution is a satisfactory approximation of a t-distribution .
Marc,
re: 3) Point 3: I don’t get this point. How can you distinguish between urbanization and an increase in greenhouse gasses per se? What would be the direct and the indirect effects of urbanization for the system considered. Again, the author is not making his point in a clear way (MH-I would have thought the comparison between the three stations clearly demonstrates a UHI effect over the Melbourne region).
These guys are biologists, not climate scientists, writing and working outside their own field when it gets to UHI. You might need to explain the difference between “anthropogenic climate change” caused by land use changes, urbanization, deforestation, agriculture, etc., narrowly defined UHI and then “GHG-caused climate change” . Some folks here at WUWT understand the differences, but I obviously this reviewer hasn’t a clue – but he does have a point!
Here is a plot of the 4 stations within 2 degrees of Melbourne from the NOAA GHCN data for mean temperature April – October. (Only stations with data after 2000 are included)
And here is a plot of the same 4 stations averaged (again April – Oct data).
When the four stations of this slightly wider area are considered, there is no significant warming.
Steve Schaper (22:05:11) :
“Peculiar, the paper is rejected for not providing proof. The point of the paper was that the original paper being criticized was flawed and did not provide proof for its position. It seems to me that the peer reviewers have reversed the burden of proof from what is proper. All that Hendrickx has to do is show that there is a possibility of bias and simply bad data in the Kearney paper. It is up to Kearney et alia to prove their thesis. Hendrickx is not required to prove a counter-thesis.”
This, and other comments further on, highlight the misunderstanding
of science within the sceptic movement. Whether you do an original
article, a reply/refutation or a review; the burden of proof is definitely
on you; in fact the acceptance of this burden and attempt to provide
better proof or at least an equally good counter-explanation is the
criteria for participation. Although MH could with time probably do
an interesting article, what he offered in his reply letter were very
generic, rather weak arguments. The referees did right.
I’m suspicious of the conclusions drawn in this paper. I’ve observed, collected, and raised butterflies and moths my entire life as a hobby. Emergence times are not tied to a 1C degree of temperature change. This would be true if the daily temperature cycle never varied by more than a few tenths of a degree.
Instead I have observed that emergence is tied to periods of average to above average temperatures. I used to live in Fremont, California and rode my bike out to Coyote Hills Park all the time. There was a population of Anise Swallowtails out there. The earliest emergence I observed was March and the latest was June. It depended on how cold and wet the Spring was.
I’ve raised Ceanothus silk moths for over ten years. The adults have an uncanny ability to hatch on the first or second day of a warm spell which could be from late March to early May.
I’ve found that the Ceanothus larva are affected by temperature. A 5 C degree increase in temperature inside the house where I keep them can speed their development up by a week. A 1 C degree increase would make little measurable difference, maybe a day or so. Larvae from the same female can end up with as much as a two week spread in development time under identical conditions. The development time data is pretty noisy.
The idea that anyone can claim adult emergence is occurring 10 days earlier due to a 1 C average temperature increase is very suspicious to me.
Marc, since you had questions about the paper did you bother to contact the authors?
Steve Schaper (22:05:11) : “Peculiar, the paper is rejected for not providing proof. The point of the paper was that the original paper being criticized was flawed and did not provide proof for its position. It seems to me that the peer reviewers have reversed the burden of proof from what is proper.”
There is no such thing as proof in the empirical sciences. The papers claims to “provide evidence for phenological shifts in the butterfly Heteronympha merope in response to regional warming in the southeast Australian city of Melbourne.” (See the abstract.)
If Marc Hendrickx wants to get something published on this he either needs to find a flaw in this paper or provide evidence of his own. Every scientist reading the paper knows it could happen that confounding processes that the authors did not account for could undermine the hypothesis. To get published Marc needs to actually find such evidence.
Marc,
3) Point 3: I don’t get this point. How can you distinguish between urbanization and an increase in greenhouse gasses per se? What would be the direct and the indirect effects of urbanization for the system considered. Again, the author is not making his point in a clear way (MH-I would have thought the comparison between the three stations clearly demonstrates a UHI effect over the Melbourne region).
I don’t have much time today, so this may have been addressed already.
Regardless, I agree with this critique per se. If the heating is due to co2 or UHI is moot. IMHO, you need elaborate that warming from UHI is a localized event. If the habitat of the insect is entirely within the confines of the area affected by UHI (12,000 sq km2), and if in fact warming does cause earlier emergence, then the authors have a valid point. If the habitat extends beyond the UHI effect (which I imagine it does), then rephrase your criticism as to the extent of the data. In other words, attack the title and premise of the original article, ie. the title and premise of the article should be changed to “Butterfly emergence affected by UHI”. If you know the range of the species, show a trend for a real rural station in that area.
And your response to commenter 3 could be similar to: The geograpical coordinates given by authors includes an area of 12,000 sq km2. However the UHI may extend to only XX area, as the outlying stations which I’ve (Marc) included do not show warming. Therefore, there is no data to support the authors contention that anthropogenic climate forcing is affecting this species in the greater part of their range.
Also, IMHO, nutrition is probably the actual causal mechanism. Better fed specimen of most species develop faster, as in the onset of the menstrual cycle in women occurs sooner with better nutritiion. One insect example:
Effects of elevated CO2 on development and larval food-plant preference in the butterfly Coenonympha pamphilus (Lepidoptera, Satyridae)
Marcel Goverde and Andreas Erhardt
Department of Integrative Biology, Section of Conservation Biology, University of Basel, St. Johanns-Vorstadt 10, CH-4056 Basel, Switzerland
Correspondence to Marcel Goverde, Melchtalstrasse 21, CH-4102 Binningen, tel. +41 (0)61 422 03 55, fax +41 (0)61 422 03 57, e-mail: goverde@ur momisuglymail.com
Copyright Blackwell Publishing Ltd
KEYWORDS
elevated carbon dioxide • plant–insect interactions • nutrient availability
Abstract
The objective of this study was to determine how increasing atmospheric CO2 change plant tissue quality in four native grassland grass species (Agrostis stolonifera, Anthoxanthum odoratum, Festuca rubra, Poa pratensis) which are all larval food-plants of Coenonympha pamphilus (Lepidoptera, Satyridae). We assessed the effect of these changes on the performance and larval food-plant preference of C. pamphilus in a greenhouse experiment. Furthermore, we tested the interactive effects of elevated CO2 and soil nutritional availability in F. rubra and its effect an larval development of C. pamphilus. In general, elevated CO2 decreased leaf water concentration, nitrogen concentration and specific leaf area (SLA), while leaf starch concentration was increased in all grass species. A species-specific reaction to elevated CO2 was only found for foliar starch concentration. P. pratensis did not increase its starch concentration under elevated CO2 conditions, whereas the other three species did. Fertilisation, investigated only for F. rubra, increased leaf nitrogen concentration and amplified the CO2-induced decrease in leaf nitrogen. Development time of C. pamphilus was on the average prolonged by two days under elevated CO2 and the prolongation differed from 0.7 to 5.3 days among food-plant species. Pupal fresh weight differed marginally between CO2 treatments. Fertilisation of the larval food-plant F. rubra shortened development time by one day and significantly increased pupal and adult fresh weights. C. pamphilus larvae showed a clear food-plant preference among grass species at the age of 36 h or older. Additionally, a change of food-plant preference under elevated CO2 was found. Larvae at ambient CO2 preferred Agrostis stolonifera and F. rubra, while under elevated CO2Anthoxanthum odoratum and P. pratensis were preferred. The present study demonstrates that larval development of C. pamphilus is affected by food-plant species and CO2 induced changes in foliar chemistry. Although we found some species-specific reactions to elevated CO2 for foliar chemistry, no such CO2 by species interaction was found for insect development. The change in food-plant preference of larvae under elevated CO2 implies potential changes in selection pressure for grass species and might therefore affect evolutionary process.
The authors keywords and citations will give you a starting point to continue your pursuit.
Occasionally herbivores have shown reduced growth (Fajer et al., 1989). In other experiments with lepidopterans, Fajer et al. documented that insect weight gain was positively correlated and consumption was negatively correlated with foliar nitrogen concentration (Fajer et al., 1989). They also found that insects that feed on plants grown in elevated CO2 have a reduced efficiency of conversion of ingested food to insect tissue. Thus, larvae could be prevented from completing development in climatically-limited environments with short growing seasons, and have increased exposure to their natural enemies (Fajer, 1989; Caulfield and Bunce, 1994), or both.
Fajer ED. 1989. The effects of enriched carbon dioxide atmospheres on plant–insect herbivore interactions: growth responses of larvae of the specialist butterfly, Junonia coenia (Lepidoptera: Nymphalidae). Oecologia 81, 514–520.[@ur momisugly DigiTop]
Fajer ED, Bowers MD, Bazzaz FA. 1989. The effects of enriched carbon dioxide atmospheres on plant–insect herbivore interactions. Science 243, 1198–1200
Lastly, and this is my take, what is the problem with emerging earlier? Who gives a rat’s ***.
I second the comment by TA (09:53:38). Include a sentence or two explaining the nature of the UHI effect, to differentiate it from warming from CO2. You referenced the Jones China paper on this subject, don’t expect the reviewer to examine your references.
Also include a satellite photograph or other means of proving the non-rural nature of the Laverton station. In fact, maybe we could get a reader in the Melbourne area to drive through Laverton with one of those UHI measurement kits to prove the point (ha!).
Change the station temperature comparison graph to take out the trend lines. They’re not needed to make the point, because the human eye can easily see that the Melbourne and Laverton stations have an upward trend while the rural station does not (except for the short period in the 40s). However, you’ll have to explain to the editor why you took the trend lines out: it is that they were misleading, because the two urban stations show linear trends in warming, while the rural station shows a rapid change in the 40s followed by no change since then.
Ask why the study only goes back to 1941, which coincidentally is roughly the year the warming trend began. Any study like this should have a “baseline”, showing that changes did not occur while temperatures were constant, but only began once temperatures started going up. If data on butterfly emergence prior to 1941 exists, it should have been included in the original study.
While your points in #2 are good, they are difficult to substantiate without direct evidence contradicting the original study. And from the comments by entomologists here, it seems the consensus (if I dare use that word!) is that cumulative temperature is one of the biggest, if not the biggest, drivers of butterfly emergence dates. You may very well have hit on some good points regarding other possible factors, in my view it will be difficult, without hard evidence, to convince the editors that the original study was flawed because of its focus on the single issue of temperature.
Your points in #1 and #3 are by far the strongest, so in the revision I would focus on those. In fact, I don’t think #1 and #3 are separate issues. For the revision, you should combine those points together to make the argument stronger. Focus on the fact that, if the authors are correct about the influence of temperature on emergence dates, their conclusions are flawed because (1) they don’t present specific sampling locations for the emergence data, and (2) they don’t account for the huge effect of UHI.
The lack of specific locations for the butterfly emergence data is a big problem with the original study. Even if the primary driver is temperature change, the UHI effect depends very strongly on location, while the overall “global warming” trend does not. So to rule out UHI, the butterfly data must be shown as a function of sampling location, not just time. There are many ways this could be presented: for example, emergence dates by year as a function of distance from the Melbourne city center.
We have good proof that local variations in temperature due to UHI completely swamp whatever underlying signal is coming from global temperature changes. You can more conclusively demonstrate that the original study’s use of the Laverton station was severely flawed — so flawed, in fact, as to negate their conclusions, because without location evidence to the contrary, the temperature changes in the area sampled likely come from UHI, not from global warming. Hammer home the point that specific emergence locations are needed because of the strong dependence of local temperature on the UHI effect.
Ian George (21:56:59)
It’s worse than that. Although the graph shows max temps back to 1910, the data only starts in 1944. Here’s why:
Hide the decline …
w.
Nobody seems to notice that referee #1 suggests correcting the
trend line for the rural station – I am refering to the graph of MH –
so that all 3 stations are compared fin the same period. In this was
done, it seems we would have three wqarming trends, some of it
could be UHI, but some would have to be, well…
Also, it appears that they have used the data from the graph (which shows a greater temperature increase from 1944-2007) rather than from the adjusted data … bad scientists, no cookies.
Robert Kral says: “Degree days are not a proxy for anything. Temperature has independent effects on insect development.”
The reason I asked was because I understand caterpillars spend some time munching on leaves. If the butterflies in this study do the same, there is a development stage before emerging as butterflies which could well involve more factors than temperature, and a simple measure of degree-days. No?
Chuck (11:17:18) :
I’m suspicious of the conclusions drawn in this paper. I’ve observed, collected, and raised butterflies and moths my entire life as a hobby. Emergence times are not tied to a 1C degree of temperature change. This would be true if the daily temperature cycle never varied by more than a few tenths of a degree.
You are right that plants/animals don’t emerge or die off because
of long term averages. But does not a clear change in average yearly
temp. imply that the triggering warm spells would come earlier, on an
average.
How come that if this very old and decidedly unscientific bozo can understand Bertrand Russell’s Flying Teapot Hypothesis, young men who cannot comprehend it come to get employed as editors of serious scientific publications? If I postulate the existence of the teapot, and perhaps its quite overwhelming influence on the emergence of Australian butterflies, it is up to me to demonstrate that it must be so. I am no scientist and nor is anyone else who cannot grasp this elementary principle.
The abstract makes claims about anthropogenic warming, not CO2-induced warming. UHI’s and GHG’s are both causes of anthropogenic warming, so discussion of UHI’s is only useful if you can prove that any UHI influences the recorded temperature in a small section of the butterfly study area.
Opportunistic collection of data over a variable wide region with increase the noise in the data, but not necessarily impart a bias. However, as the road system has improved, it is possible that this has increased access to the warmer areas of the study region, causing more butterflies to be collected from warmer areas. This could be important near the ocean.
The DECADAL averages in Figure 1a could hide a multitude of sins. If earlier appearance of butterflies is due to more rapid maturation in warmer surroundings, then ANNUAL changes in appearance should show correlation with ANNUAL changes in temperature. This is best explored with the correlation coefficient. Other environmental factors that might influence butterfly hatching (genetic drift, predator changes, land-use changes) will produce gradual changes like those seen in Figure 1a.
There is a thermodynamic reason for plotting 1/development time vs temperature in Figure 1c, but this makes it very difficult to convert temperature change into a change in development time. The difference between 0.02 and 0.03 on the vertical scale (temperature ca 5 degC) is the difference between 50 and 33 days, while the difference between 0.10 and 0.11 (temperature ca 20 degC) is 10 days and 9 days. This makes it clear that butterflies mature mostly during the warmer daytime than during the cool night. So it would make sense to consider the relationship between the daily maximum temperature and butterfly appearance rather than the daily average temperature. GHG’s and UHI’s are supposed to have a bigger impact on minimum temperatures.