The Specter of Species Extinction
XI. Discussion of Real-World Observations
Are significant impacts of global warming "already discernable in animal and plant populations," as Root et al. claim? Is climate change "already affecting living systems," as Parmesan and Yohe contend? The answer to both of these questions in many but not all of the cases they cite is a definite yes. Much of the biosphere has indeed responded to the global warming of the past century and a half that has transformed what we have come to call the Little Ice Age into what can now be called the Modern Warm Period. But it has not - we repeat not - brought us to the verge of biospheric disintegration, as the world's climate alarmists would have everyone believe. In fact, it has done just the opposite, aided in no small part by the concomitant rise in the air's CO2 content.
To substantiate this fact, ironically, we need look no further than to the very papers that are used by Root et al. and Parmesan and Yohe to suggest, as Root has claimed, that "we're sitting at the edge of a mass extinction." And when we do, we find that the studies they cite do not imply anything of the kind.
It is true that some species of plants and animals have indeed moved poleward and upward in response to 19th and 20th century warming; but they have not been forced to do so. The poleward and upward extensions of the cold-limited boundaries of these species' ranges have been opportunistic movements, movements that have enabled them to inhabit regions that previously were too cold for them. But where it has been predicted that species would either be compelled to move towards cooler regions or suffer death, i.e., at the heat-limited boundaries of their ranges, they have in many instances, if not most instances, succumbed to neither alternative. As a result, instead of suffering range contractions, indicative of advancement towards extinction, these species have experienced range expansions, indicative of a propensity to avoid extinction.
We note also, with respect to latitudinal movements, that it is not necessary for the heat-limited boundary of a species' range to remain totally stationary for the CO2-induced global warming extinction hypothesis to be found null and void. If the heat-limited boundary merely moves slower than the cold-limited boundary in response to an increase in temperature, a range expansion will occur that makes extinction even less likely than it was before the warming occurred. What is more, the viability of species in a warming world can be maintained by relaxing even this condition; for if a species' heat-limited boundary moves at the same speed as its cold-limited boundary, its range size will remain fairly constant (depending upon local geographical constraints, of course), which also precludes the possibility of extinction. In fact, if the cold-limited and heat-limited boundaries of a species' range are widely separated, as in the case of the butterfly studied by Parmesan (1996), even if the heat-limited boundary were to move faster than the cold-limited boundary, the large temperature difference between the two boundaries would prevent the heat-limited boundary from ever merging with the cold-limited boundary for the degree of warming that would be likely to occur in the real world. Hence, there is currently not the slightest shred of evidence that what is "already discernable in animal and plant populations," in the words of Root et al., and "already affecting living systems," in the words of Parmesan and Yohe, portends the eminent or even far-distant extinction of a single species of plant or animal.