flowering species (Sherry et al., 2007). In the future, increasing temperatures may also affect the production, toxicity, and/or pollen-producing capacity of allergenic and toxic plants, including ragweed and poison ivy (Mohan et al., 2008; Shea et al., 2008; Ziska et al., 2009). Allergy incidence may also be increased by interactions between airborne allergens and air pollution (D’Amato and Cecchi, 2008). Uncertainties in future emissions and the coupling between climate, air quality, and ecosystem models, however, render speculative any determination of the degree of change (Bernard and Ebi, 2001; Gamble et al., 2008).
As the climate changed throughout the past millennia, species shifted to track temperature, precipitation, and other weather factors (Graham and Grimm, 1990; Overpeck et al., 1992). The geographic range of any species includes only areas where individuals can endure the extreme temperature and water stress occurring at those locations (Gordon,1982; Chown and Gaston, 1999). Indeed, the ranges of various songbirds in North America are limited by the amount of metabolic energy an individual must exert to stay alive (Root, 1988a,b). Warming in the late-Quaternary resulting in species tracking the changing climate gradient (Graham and Grimm, 1990). Additionally, these species differentially tracked their own unique set of climatic factors, which resulted in many species occurring in unexpected areas (Graham and Grimm, 1990) and new species groups being formed (Overpeck et al., 1992; Hobbs et al., 2009).
Today species continue to shift and change with current climate change. Additionally, if we remain on the “Business as Usual” scenario, then on a sustained global basis the expected rate of change in temperature in the next few decades could be higher than most species have endured over millennia (Hoeg-Guldberg et al., 2007; Loarie et al., 2009; NRC, 2009). In addition the face of the planet is very different from how it has ever been before because people have altered it considerably by constructing various structures on the landscape, such as cities, farms, and roadways. These frequently make movement of species across an area difficult. This is particularly true for species that are slow moving, such as turtles, but it is also true for animals that can move more quickly, including birds, bats, and butterflies. Even with these impediments, many species are changing with the globally changing climate. Indeed, with an increase in the average global