The Specter of Species Extinction
VII. Discussion of the Results of Root et al.'s Tier 1 and Tier 2 Studies
Of the twenty-four Tier 1 (T1) and Tier 2 (T2) studies analyzed by Root et al., five of them, according to our analyses, directly refute the CO2-induced global warming extinction hypothesis. In response to regional warming, two of these studies (T1.4, T1.5) describe opportunistic poleward extensions of the cold-limited range boundaries of a number of species that were accompanied by no forced changes in their heat-limited range boundaries, leading to actual range expansions, which should make extinction even less likely for the studied species than it was before the warming. Two other studies (T1.7, T1.8) describe upslope extensions of the cold-limited range boundaries of lower-elevation species that did not result in any loss of higher-elevation species. Another study (T2.4) demonstrated that certain species, when faced with a warming-induced impetus to migrate, dramatically changed both their behavior and physical characteristics in ways that no one had previously believed possible, allowing them to "cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started."
Over half of the T1 and T2 studies analyzed by Root et al. were simply examples of the opportunistic poleward or upward extensions of species' cold-limited range boundaries in response to regional or global warming, a phenomenon that reveals absolutely nothing about the responses of their heat-limited range boundaries, knowledge of which is critical to an evaluation of the CO2-induced global warming extinction hypothesis. Nine of these studies dealt with latitudinal range extensions (T1.2, T1.3, T1.10, T1.11, T2.1, T2.5, T2.9, T2.10, T2.11), three with elevational range extensions (T1.9, T2.6, T2.8), and one with some of each (T2.3). These studies demonstrate what should be almost prenatal knowledge: if the climate warms, species of both plants and animals will expand into areas where it was previously too cold for them to live, a phenomenon that suggests an ability to avoid extinction rather than succumb to it.
The remaining six T1 and T2 studies analyzed by Root et al. were hybrids of sorts, which really did not address the subject of species' range responses to global warming. The upslope migrations discussed in T1.1, for example, turned out to be due to environmental changes induced by local logging practices rather than regional warming. Likewise, the cold-limited boundary extension of T1.6 may also have been caused by something other than warming; and the results of T2.2 were so complex that the authors could not decide what caused the range expansions. Somewhat similarly, the authors of T2.13, although demonstrating a latitudinal shifting of species, were not able to conclude unequivocally that it was due to regional warming; while the latitudinal heat-limited boundary extensions discussed in T2.12 were due to cooling and increased precipitation. Finally, the range expansions described in T2.7 would not even have occurred if the exotic species involved had not been transported into the area of study from half-way around the world.
In light of these observations, it is clear that the scientific articles studied by Root et al. that are most applicable to the CO2-induced global warming extinction hypothesis fail to provide a single piece of evidence in support of it. In fact, most of the knowledge gleaned from them does not even address the subject; while that which is pertinent actually contradicts the hypothesis.