In this Summary we review a number of real-world studies that suggest that animals respond in like manner, mimicking the shifts and non-shifts of the cold- and heat-limited boundaries of the ranges of the plants on which they depend for food, either directly in the case of herbivores or indirectly in the case of carnivores, whose range adjustments may depend upon the range adjustments of animal prey further down the food chain that are dependent on the range adjustments of the plants that ultimately sustain all life above them.

Parmesan et al. (1999) analyzed distributional changes, broadly spread over the past century, of non-migratory butterflies whose northern boundaries were in northern Europe and whose southern boundaries were in southern Europe or northern Africa.  A northern boundary analysis of the ranges of 52 species revealed that northern boundaries shifted northward for 65% of them, remained stable for 34% of them, and shifted southward for 2% of them, while a southern boundary analysis of the ranges of 40 species revealed that their southern boundaries shifted northward for 22% of them, remained stable for 72% of them, and shifted southward for 5% of them.  The consequences of the 0.8°C of warming that occurred in Europe over the course of the 20th century, therefore, have been largely beneficial for these butterflies.  Since "nearly all northward shifts involved extensions at the northern boundary with the southern boundary remaining stable," in the words of the authors, "most species effectively expanded the size of their range when shifting northwards."

Thomas and Lennon (1999) analyzed the distributions of British birds over a 20-year period of global warming, looking for climate-induced changes in their breeding ranges.  They found that the northern margins of southerly species' breeding ranges shifted northward by an average of 19 km from 1970 to 1990, while the southern margins of northerly species' breeding ranges shifted not at all, in the mean.  This finding was stated by them to be similar to the results obtained for European butterflies, "for which the northern margins have expanded more than the southern margins have retracted," and they attributed both the bird results and the butterfly results to the effects of global warming as experienced in the regions studied.

Lloyd et al. (1998) evaluated the relationship between bird abundance and a number of large-scale vegetation features at the Buenos Aires National Wildlife Refuge in southeastern Arizona in an effort to understand changes that occur within bird communities as a result of changes in ecosystem composition, specifically, changes that have arisen due to a recent documented expansion of woody tree species into this region.  Among the following variables - overall grass, herb and shrub cover, percent cover of native grasses, percent cover of an introduced grass, average size of mesquite trees, and the density of mesquite trees - only the density and distribution of mesquite trees were found to influence bird populations; and in this regard, total bird abundance was found to increase with increasing mesquite density.  In addition, the researchers report that "greater bird species richness [was] found on plots with higher mesquite densities."

The results of this study demonstrate that both the total number and species richness of birds have been enhanced by the expansion of mesquite trees into this former grassland, which latter phenomenon is one of the many consequences of the historical and ongoing rise in the air's CO2 content (see Range Expansion (Plants) in our Subject Index).  Under higher CO2 concentrations, trees that were previously unable to grow in grassland regions due to certain temperature and/or moisture restrictions are now able to do so quite successfully; and it appears that their presence is having a pronounced positive effect on bird abundance and biodiversity.

Norment et al. (1999) summarized and compared the results of many surveys of bird and mammal populations along the Thelon River and its tributaries in the Canadian Northwest Territories from the 1920s through much of the 1990s.  Over that period, three bird species expanded their breeding ranges southward, nine expanded northward, and sixteen were observed to be new to the area.  Red squirrel, moose, porcupine, river otter and beaver were also found to have established themselves in the area in recent years, significantly increasing its biodiversity.  The researchers say that the primarily northward range expansions may be explained by a warming trend at the northern treeline during the 1970s and 1980s.  In addition, they note that the influx of new species may also be due to increasing populations in more southerly areas.  In either case, we have a situation where birds and mammals appear to be faring quite well - could it actually be said they are thriving? - in the face of rising temperatures in this forest-tundra landscape.

In a somewhat similar situation, Saether et al. (2000) studied the responses of a small passerine songbird of southern Norway (Cinclus cinclus) to variations in mean winter temperature and precipitation over a period of twenty years.  After developing a model based on their observations, they used it to determine the response of the birds to a 2.5°C increase in air temperature, such as is predicted to occur by several climate models in response to a doubling of the air's CO2 concentration.  It revealed that the Cinclus cinclus population of the region would likely increase by 50% or more, much as has been found to have already occurred to a lesser degree among numerous species of butterflies and birds throughout Britain and other parts of Europe in response to the lesser warming of the 20th century.

In a study that calls for caution in modeling bird responses to global warming, Visser et al. (2003) examined laying dates of 24 populations of Parus major and P. caeruleus in six European countries from 1979 to 1998, over which period several, but not all, of the locations studied exhibited increases in near-surface air temperature.  They report finding that "the phenological response to large-scale changes in spring temperature varies across a species' range, even between populations situated close to each other."  What is more, they find that "this variation cannot be fully explained by variation in the temperature change during the pre- and post-laying periods."  Noting that their results "show the value of replicating population studies across parts of a species' range, as the effects of climate change may differ, even within a single species, on a small geographical scale," they suggest that great caution be exercised so as not to conclude too much from studies of bird responses to warming that are not massively replicated across large areas.  Nevertheless, we note that the modeling study of Saether et al. produced results that were harmonious with what has been observed throughout most of Europe and elsewhere.

Shifting to a consideration of something other than birds and butterflies, Hickling et al. (2005) analyzed changes in the northern and southern range boundaries of 37 non-migratory British dragonfly and damselfly species - 4 of which have northern ranges, 24 of which have southern ranges, and 9 of which are ubiquitous - between the two 10-year periods 1960-70 and 1985-95.  This work revealed that the sizes of the ranges of all but two of the 37 species increased between the two 10-year periods; and they state that their "findings that species are shifting northwards faster at their northern range margin than at their southern range margin, are consistent with the results of Parmesan et al. (1999)," adding that "this could suggest that species at their southern range margins are less constrained by climate than by other factors."  We agree, noting that this is the primary thesis of our major report The Specter of Species Extinction: Will Global Warming Decimate Earth's Biosphere?

Last of all, in a study of rocky intertidal marine animals found along the Pacific coast of Chile, Rivadeneira and Fernandez (2005) determined mid-20th-century southern endpoints of the distributions of ten species of chitons and gastropods from museum collections and literature reviews, while current endpoints were obtained from field sampling conducted between 1998 and 2000.  Based on this work, they report that "of the 10 species analyzed, six presented significant changes in their southern [poleward] limit, whereas four species exhibited no significant shifts."  Furthermore, they say that "of the six species showing significant changes, only two expanded their southern limit, while the four remaining species exhibited significant range contractions," that is, their southern boundaries moved in a direction opposite to the direction climate alarmists and we claim they should have moved in response to rising temperatures.  The results of the Chilean marine biologists thus suggest that the Pacific coast of Chile may be another one of the many parts of the earth that have not experienced unusual warming in recent decades.  In fact, their analyses of the temperature records of five stations along the Chilean coast actually indicate cooling over the last half century at two of them; and they cite Rosenbluth et al. (1997) as evidence for their statement that "a cooling trend of air temperature has been recorded during the last century between 38°S and 41°S."

In conclusion, it is clear that where there has been confirmed regional warming over the time periods investigated, the vast majority of studies of animal range adjustments have revealed opportunistic poleward expansions of their cold-limited boundaries with little to no change in the locations of their (supposedly) heat-limited boundaries.  This behavior, as noted in the introduction to this summary, is not one of animal species rushing, or even inching, towards extinction, as so many climate alarmists claim is occurring.  Rather, it is one where they are moving in the exact opposite direction, fortifying themselves against the possibility of extinction.

References
Hickling, R., Roy, D.B., Hill, J.K. and Thomas, C.D.  2005.  A northward shift of range margins in British Odonata.  Global Change Biology 11: 502-506.

Lloyd, J., Mannan, R.W., Destefano, S. and Kirkpatrick, C.  1998.  The effects of mesquite invasion on a southeastern Arizona grassland bird community.  Wilson Bulletin 110: 403-408.

Norment, C.J., Hall, A. and Hendricks, P.  1999.  Important bird and mammal records in the Thelon River Valley, Northwest Territories: Range expansions and possible causes.  The Canadian Field-Naturalist 113: 375-385.

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.

Rivadeneira, M.M. and Fernandez, M.  2005.  Shifts in southern endpoints of distribution in rocky intertidal species along the south-eastern Pacific coast.  Journal of Biogeography 32: 203-209.

Rosenbluth, B., Fuenzalida, H.A. and Aceituno, P.  1997.  Recent temperature variations in southern South America.  International Journal of Climatology 17: 76-85.

Saether, B.-E., Tufto, J., Engen, S., Jerstad, K., Rostad, O.W. and Skatan, J.E.  2000.  Population dynamical consequences of climate change for a small temperate songbird.  Science 287: 854-856.

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

Visser, M.E., Adriaensen, F., van Balen, J.H., Blondel, J., Dhondt, A.A., van Dongen, S., du Feu, C., Ivankina, E.V., Kerimov, A.B. de Laet, J., Matthysen, E., McCleery, R., Orell, M. and Thomson, D.L.  2003.  Variable responses to large-scale climate change in European Parus populations.  Proceedings of the Royal Society of London B 270: 367-372.