December 20, 2006

Some Good News for Christmas–Reptile and Butterflies Flourishing

Filed under: Adaptation, Animals

How many times have you seen articles in newspapers about global warming causing the extinction of some frog, toad, lizard, butterfly, or you name it, specie? If today’s newspaper doesn’t contain such an article, Google “Global Warming and Extinction” and enjoy over two million sites. Repeatedly, if you see “Global Warming” and any specie in the title of an article, heaven help members of that specie, right?

What is odd is that literally thousands of professional journal articles show that virtually all plants benefit from elevated atmospheric carbon dioxide levels with or without any increase in temperature. With all the goodness in the world of flora, why do the fauna of the planetary ecosystem seem so vulnerable? The dirty secret is that the literature is full of articles showing the animal kingdom benefiting from changes that are underway.

For example, a recent issue of Global Change Biology contains an article about global warming and a “positive fitness response” in mountain lizards in Europe. Did these lizards not get the memo about extinctions? Maybe the lizards haven’t read their e-mail about global warming making things tough on lizards around the world? If nothing else, these lizards have obviously not been reading newspapers over the past decade!

A team of scientists from Spain and France decided to study mountain lizards in southern France in an area that has warmed over the past few decades. Chamaillé-Jammes et al. begin their article stating “Assessing species’ responses to climate change is one of the greatest challenges for ecologists because global warming is expected to be a major threat for biodiversity in coming years.” That sentence could be used to lead off literally hundreds of articles every year. Next, they note that “A recent study showed that up to 37% of species on Earth might be threatened by extinction because of the recent rise in temperature.” In that context, they state “isolated (e.g. island, mountain) populations or species with limited dispersal abilities appear at especially high risk as available altitudinal or latitudinal gradient is limited. Global warming-driven extinction in these situations indeed has already been reported.” One would never expect at this point that they will conduct the study and learn how the mountain lizards are benefiting from warming.

They collected data on common lizards from southern France and found “that individual body size dramatically increased in all the four populations studied over the past 18 years. This increase in body size in all age classes appeared related to a concomitant increase in temperature experienced during the first month of life (August).” Further, the write “yearling snout-vent-length increased by about 28%. As a result, adult female body size increased markedly, and, as fecundity is strongly dependent on female body size, clutch size and total reproductive output also increased.” They find that “In the same time, adult survival was also positively correlated to the temperature in spring.” They conclude that “All fitness components investigated therefore responded positively to the increase in temperature, such that it might be concluded that the common lizard has been advantaged by the shift in temperature.” We sincerely doubt that the Chamaillé-Jammes et al. team won any awards with such a positive message about warming!

OK, so there is some lizard in France that is benefiting from warming, but what about the butterflies that seem in desperate straights. Butterfly extinction just seems so unacceptable – they are pretty, harmless, loved by children – a perfect and innocent member of the biosphere, and therefore, a poster child for global warmers. A recent paper in the Proceedings of the Royal Society by a team of scientists in the United Kingdom has some interesting conclusions regarding butterfly response to warming.

Menéndez et al. investigate changes in species richness using the well-monitored British butterfly fauna that include 54 species (not including continental migrants). They note that “Britain is a relatively species-poor region due to its cool-temperate climate and the butterfly fauna shows a species-richness gradient with more species found in hotter areas in the south.” In this investigation, the team tests “whether average species richness of resident British butterfly species has increased in recent decades, whether these changes are as great as would be expected given the amount of warming that has taken place.” They “compare patterns of diversity in two periods, 1970–82 and 1995–99, when butterfly distributions were recorded comprehensively.”

Menéndez et al. conclude that “average species richness of the British butterfly fauna at 20×20 km grid resolution has increased since 1970–82, during a period when climate warming would lead us to expect increases.” They interestingly note that many others use the term “extinction debt” to denote the time delay between environmental change and the extinctions that will eventually take place as a result of those environmental changes. They conclude, “Just as important in the context of climate change (and species invasions) are ‘colonization lags’ to denote the time delay between environmental changes and colonization events.”

These two recent articles are among many that show that fauna throughout the world can benefit from higher temperatures, but these findings absolutely never receive a scintilla of coverage in major news outlets. If the studies on British butterflies or French lizards had come up with negative consequences of warming, you would have seen the results in your local newspapers. But good news about the environment seems to be unworthy news, everywhere except World Climate Report.

References:

Chamaillé-Jammes, S., M. Massott, P. Aragon, and J. Clobert, 2006, Global warming and positive fitness response in mountain populations of common lizards Lacerta vivipara. Global Change Biology, 12, 392–402.

Menéndez, R., A.G. Megıas, J.K. Hill, B. Braschler, S.G. Willis, Y. Collingham. R. Fox, D.B. Roy, and C.D. Thomas, 2006, Species richness changes lag behind climate change. Proceedings of the Royal Society, B., 273, 1465–1470.
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