The Specter of Species Extinction
I. Introduction
Will global warming decimate earth's biosphere? Many scientists who are concerned about global warming have long contended the increase in temperature predicted to result from the ongoing rise in the air's CO2 content will be so great and occur so fast that many species of plants and animals will not be able to migrate poleward in latitude or upward in elevation rapidly enough to avoid extinction as they are forced to seek cooler living conditions:
Woodwell (1989): "The changes expected are rapid enough to exceed the capacity of forests to migrate or otherwise adapt."
Davis (1989): "trees may not be able to disperse rapidly enough to track climate."
Gear and Huntley (1991): "the maximum [migration] rates attainable by ... long-lived sessile organisms [are] more than an order of magnitude less than those required to maintain equilibrium with forecast anthropogenically induced climate changes."
Root and Schneider (1993): "changes in global climate are expected to occur ... too fast for evolutionary processes such as natural selection to keep pace. Such constraints ... could substantially enhance the probability of extinction of numerous species."
Dyer (1995): "The magnitude of the projected warming is considerable; the rate at which it is predicted to occur is unprecedented. There is genuine reason for concern that the extent of range shifts will exceed the dispersal abilities of many plant species."
Malcolm and Markham (2000): "rapid rates of global warming are likely to increase rates of habitat loss and species extinction .... many species may be unable to shift their ranges fast enough to keep up with global warming."
Malcolm et al. (2002): "Migration rates required by the warming are unprecedented by historical standards, raising the possibility of extensive, and in many cases, catastrophic, species loss."
Root et al. (2003): "rapid temperature rise and other stresses ... could ... lead to numerous extirpations and possibly extinctions."
Parmesan and Yohe (2003) and Root et al. (2003) suggest that the CO2-induced global warming extinction phenomenon is already underway, with its initial effects being manifest in numerous "mini-migrations" of plant and animal populations throughout the world. However, when atmospheric CO2 concentrations rise sufficiently fast concurrently, many experiments have demonstrated that rising temperatures should not force plants to migrate, although they may provide them with the opportunity to do so. In addition, there are a number of other ways in which plants are able to adapt to rising temperatures without resorting to migration. Finally, nearly all of the real-world observations that are routinely cited as evidence for the validity of the CO2-induced global warming extinction hypothesis not only do not support it, they actually refute it, as we demonstrate later in this report.