In a study of Lotus corniculatus (a cyanogenic plant that produces foliar cyanoglycosides to deter against herbivory by insects) and the Common Blue Butterfly (Polyommatus icarus, which regularly feeds upon L. corniculatus because it possesses an enzyme that detoxifies cyanide-containing defensive compounds), Goverde et al. (1999) collected four genotypes of L. corniculatus differing in their concentrations of cyanoglycosides and tannins (another group of defensive compounds) near Paris, France.  They then grew them in controlled-environment chambers maintained at atmospheric CO2 concentrations of 350 and 700 ppm, after which they determined the effects of the doubled CO2 concentration on leaf quality and allowed the larvae of the Common Blue Butterfly to feed upon the plants' leaves.  This work revealed that elevated CO2 significantly increased leaf tannin and starch contents in a genotypically-dependent and -independent manner, respectively, while decreasing leaf cyanoglycoside contents independent of genotype.  These CO2-induced changes in leaf chemistry increased leaf palatability, as indicated by greater dry weight consumption of CO2-enriched leaves by butterfly larvae.  In addition, the increased consumption of CO2-enriched leaves led to greater larval biomass and shorter larval development times, positively influencing the larvae of the Common Blue Butterfly.  Hence, it is not surprising that larval mortality was lower when feeding upon CO2-enriched as opposed to ambiently-grown leaves.

Goverde et al. (2004) grew L. corniculatus plants once again, this time from seed in tubes recessed into the ground under natural conditions in a nutrient-poor calcareous grassland, where an extra 232 ppm of CO2 was supplied to them via a Screen-Aided CO2 Control (SACC) system (Leadley et al., 1997, 1999), and where insect larvae were allowed to feed on the plants (half of which received extra phosphorus fertilizer) for the final month of the experiment.  Information gleaned from following these procedures indicated that the atmospheric CO2 enrichment employed in this experiment increased the total dry weight of plants growing on the unfertilized soil by 21.5% and that of plants growing on the phosphorus-enriched soil by 36.3%.  However, the elevated CO2 treatment had no effect on pupal and adult insect mass, although Goverde et al. report there were "genotype-specific responses in the development time of P. icarus to elevated CO2 conditions," with larvae originating from different mothers developing better under either elevated CO2 or ambient CO2, while for still others the air's CO2 concentration had no effect on development.

In another study by some of the same team of researchers, Goverde et al. (2002) raised larvae of the satyrid butterfly (Coenonympha pamphilus) in seminatural undisturbed calcareous grassland plots exposed to atmospheric CO2 concentrations of 370 and 600 ppm for five growing seasons.  They found that the elevated CO2 concentration increased foliar concentrations of total nonstructural carbohydrates and condensed tannins in the grassland plants; but in what is often considered a negative impact, they found that it also decreased foliar nitrogen concentrations.  Nevertheless, this phenomenon had no discernible impact on butterfly growth and performance.  Larval development time, for example, was not affected by elevated CO2, nor was adult dry mass.  In fact, the elevated CO2 increased lipid concentrations in adult male butterflies by nearly 14%, while it marginally increased the number of eggs in female butterflies.  The former of these responses is especially important, because lipids are used as energy resources in these and other butterflies, while increased egg numbers in females also suggests an increase in fitness.

Turning to the study of temperature effects on butterflies, Parmesan et al. (1999) analyzed distributional changes over the past century of non-migratory species whose northern boundaries were in northern Europe (52 species) and whose southern boundaries were in southern Europe or northern Africa (40 species).  This work revealed that the northern boundaries of the first group shifted northward for 65% of them, remained stable for 34%, and shifted southward for 2%, while the southern boundaries of the second group shifted northward for 22% of them, remained stable for 72%, and shifted southward for 5%, such that "nearly all northward shifts involved extensions at the northern boundary with the southern boundary remaining stable."

This behavior is precisely what we would expect to see if the butterflies were responding to shifts in the ranges of the plants upon which they depend for their sustenance, because increases in atmospheric CO2 concentration tend to ameliorate the effects of heat stress in plants and induce an upward shift in the temperature at which they function optimally.  These phenomena tend to cancel the impetus for poleward migration at the warm edge of a plant's territorial range, yet they continue to provide the opportunity for poleward expansion at the cold edge of its range.  Hence, it is possible that the observed changes in butterfly ranges over the past century of concomitant warming and rising atmospheric CO2 concentration are related to matching changes in the ranges of the plants upon which they feed.  Or, this similarity could be due to some more complex phenomenon, possibly even some direct physiological effect of temperature and atmospheric CO2 concentration on the butterflies themselves.  In any event, in the face of the 0.8°C of "dreaded" global warming that occurred in Europe over the 20th century, the consequences for European butterflies were primarily beneficial.  Since "nearly all northward shifts involved extensions at the northern boundary with the southern boundary remaining stable," as Parmesan et al. describe the situation, "most species effectively expanded the size of their range when shifting northwards."

Across the Atlantic in America, Fleishman et al. (2001) used comprehensive data on butterfly distributions from six mountain ranges in the US Great Basin to study how butterfly assemblages of that region may respond to IPCC-projected climate change.  Whereas prior more simplistic analyses of the type used by climate alarmists to gain support for their anti-CO2 campaigns have routinely predicted the extirpation of great percentages of the butterfly species in this region in response to model-predicted increases in air temperature presumed to be driven by past and projected increases in atmospheric greenhouse gas concentrations, Fleishman et al.'s study revealed that "few if any species of montane butterflies are likely to be extirpated from the entire Great Basin (i.e., lost from the region as a whole)."  In discussing their results, they note that "during the Middle Holocene, approximately 8000-5000 years ago, temperatures in the Great Basin were several degrees warmer than today."  Thus, they go on say that "we might expect that most of the montane species - including butterflies - that currently inhabit the Great Basin would be able to tolerate the magnitude of climatic warming forecast over the next several centuries."  Consequently, it would appear that even if the global warming projections of the IPCC were true - which we sincerely believe they are not - the many predictions of biological extinctions associated with those projections are most certainly false.

Returning to the British Isles, Thomas et al. (2001) documented an unusually rapid expansion of the ranges of two butterfly species (the silver-spotted skipper butterfly and the brown argus butterfly) along with two cricket species (the long-winged cone-head and Roesel's bush cricket).  In fact, they write that the warming-induced "increased habitat breadth and dispersal tendencies have resulted in about 3- to 15-fold increases in expansion rates."

In commenting on these findings, Pimm (2001) truly states the obvious when he says that the geographical ranges of these insects are "expanding faster than expected" and that the synergies involved in the many intricacies of the range expansion processes are also "unexpected."  But does he suggest that these population-enhancing and species-richness-increasing phenomena might possibly bode well for earth's biosphere?  Of course not, for that would be politically incorrect.  Rather, he pessimistically writes in the lead-in to his commentary that "other species may not be quite so lucky," and he concludes his treatise equally pessimistically by stating that "the broad lesson from Thomas and colleagues' results should not be awe at how quickly a few species benefit from global change, but concern with how rapidly many may be harmed by it."

Isn't it amazing how good news - even news so good that we stand in "awe" of it - brings forth even further predictions of disaster from those enamored of the CO2-induced global warming hypothesis?  And isn't it amazing that the benefits of the regional warming are said to be restricted to but "a few species," when similar warming-induced range expansions have been documented by Parmesan et al. (1999) for literally dozens of European butterfly species? ... and by Thomas and Lennon (1999) for several species of British birds?  Then again, maybe it's not surprising, when science becomes politicized!

Reference
Fleishman, E., Austin, G.T. and Murphy, D.D.  2001.  Biogeography of Great Basin butterflies: revisiting patterns, paradigms, and climate change scenarios.  Biological Journal of the Linnean Society 74: 501-515.

Goverde, M., Bazin, A., Shykoff, J.A. and Erhardt, A.  1999.  Influence of leaf chemistry of Lotus corniculatus (Fabaceae) on larval development of Polyommatus icarus (Lepidoptera, Lycaenidae): effects of elevated CO2 and plant genotype.  Functional Ecology 13: 801-810.

Goverde, M., Erhardt, A. and Niklaus, P.A.  2002.  In situ development of a satyrid butterfly on calcareous grassland exposed to elevated carbon dioxide.  Ecology 83: 1399-1411.

Goverde, M., Erhardt, A. and Stocklin, J.  2004.  Genotype-specific response of a lycaenid herbivore to elevated carbon dioxide and phosphorus availability in calcareous grassland.  Oecologia 139: 383-391.

Leadley, P.W., Niklaus, P., Stocker, R. and Korner, C.  1997.  Screen-aided CO2 control (SACC): a middle-ground between FACE and open-top chamber.  Acta Oecologia 18: 207-219.

Leadley, P.W., Niklaus, P.A., Stocker, R. and Korner, C.  1999.  A field study of the effects of elevated CO2 on plant biomass and community structure in a calcareous grassland.  Oecologia 118: 39-49.

Parmesan, C., Ryrholm, N., Stefanescu, C., Hill, J.K., Thomas, C.D., Descimon, H., Huntley, B., Kaila, L., Kullberg, J., Tammaru, T., Tennent, W.J., Thomas, J.A. and Warren, M.  1999.  Poleward shifts in geographical ranges of butterfly species associated with regional warming.  Nature 399: 579-583.

Pimm, S.L.  2001.  Entrepreneurial insects.  Nature 411: 531-532.

Thomas, C.D., Bodsworth, E.J., Wilson, R.J., Simmons, A.D., Davies, Z.G., Musche, M. and Conradt, L.  2001.  Ecological and evolutionary processes at expanding range margins.  Nature 411: 577-581.

Thomas, C.D. and Lennon, J.J.  1999.  Birds extend their ranges northwards.  Nature 399: 213.