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The Butterflies of Canada's Boreal Forests
Reference
Westwood, A.B. and Blair, D. 2010. Effect of regional climate warming on the phenology of butterflies in boreal forests in Manitoba, Canada. Environmental Entomology 39: 1122-1133.

Background
The authors write that "climate changes, especially rapid changes, can have profound effects on natural ecosystems and have subsequent effects on the distribution of terrestrial biota." This concept is correct; and it is widely promoted by climate alarmists. However, these negativistic purveyors of bad news generally foresee only deleterious consequences of the phenomenon. So, is their "slant" on the subject the most correct?

What was done
In a study germane to this question, Westwood and Blair measured the responses of 19 common butterfly species of the boreal forests of Manitoba (Canada) to temperature changes experienced there over the period 1971-2004, focusing on each species' date of first appearance, week of peak abundance, and length of flight period.

What was learned
The two Canadian researchers report that spring and summer temperatures were little changed over the course of the research period and, consequently, that "adult butterfly response was variable for spring and summer months." However, autumn temperatures warmed significantly; and they observed that "13 of 19 species showed a significant increase in flight period extending longer into the autumn," when "flight period extensions increased by 31.5 13.9 days over the study period." And in this regard, they note that "two species, Junonia coenia and Euphydryas phaeton, increased their northerly ranges by ~ 150 and 70 km, respectively."

What it means
Quoting Westwood and Blair, "warmer autumns and winters may be providing opportunities for range extensions of more southerly butterfly species held at bay by past climatic conditions." In addition, they note that other investigators have obtained similar positive results, stating that "northward expansions in butterfly species range correlating with northward shifts in isotherms have been documented in both Europe and North America (Karl et al., 1996; Parmesan, 1996; Parmesan et al., 1999; Hill et al., 1999; Hickling et al., 2006)," while indicating that "in Canada, the Gorgone checkerspot (Chlosyne gorgone, Hubner) and the Delaware skipper (Anatryone logan, W.H. Edwards) have recently expanded their northern ranges significantly (Kerr, 2001)." And it can readily be appreciated that these species, by expanding their ranges, have tended to better buffer themselves against those forces (both anthropogenic and natural) that truly do have significant negative consequences.

References
Hickling, R., Roy, D.B., Hill, J.K., Fox, R. and Thomas, C.D. 2006. The distributions of a wide range of taxonomic groups are expanding polewards. Global Change Biology 12: 450-455.

Hill, J.K., Thomas, C.D. and Huntley, B. 1999. Climate and habitat availability determine 20th century changes in a butterfly's range margin. Proceedings of the Royal Society of London, Series B 266: 1197-1206.

Karl, T.R., Knight, R.W., Easterling, D.R. and Quayle, R.G. 1996. Indices of climate change for the United States. Bulletin of the American Meteorological Society 77: 279-292.

Parmesan, C. 1996. Climate and species' range. Nature 382: 765-766.

Kerr, J.K. 2001. Butterfly species richness patterns in Canada: energy, heterogeniety, and the potential consequences of climate change. Conservation Ecology 5: 10.

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.

Reviewed 1 December 2010