South Texas Climate 2100: Potential Ecological and Wildlife Impacts

In South Texas, the impacts of increased temperature and atmospheric carbon dioxide (CO 2) on the ecological relationships that provide the foundations for wildlife habitats and populations are potentially huge, but largely unknown at present. This is because little research attention has been paid to this issue, which is unfortunate because wildlife are culturally and economically important in this ecological region of a state were wildlife has an annual economic value conservatively estimated at about four billion dollars. Field experiments conducted outside of Texas provide equivocal results with respect to how people think grassland and perhaps shrubland vegetation will respond to increased temperatures and CO 2. If drying trends accompany increases in heat, then many species of amphibians will clearly be at risk. With respect to reptiles, it is unknown, but postulated that rising heat could limit daily activities of lizards, and increase the growth rates of some turtles. Some reptile sex ratios may be influenced by increased heat, because gender is determined by the temperature at which eggs are incubated in some species. Mammalian species in Big Bend National Park are predicted to experience at least a 25% turnover because of a vegetation shift from arid shrub lands to C4 grasslands. If drying trends and extended periods of drought persist, then the annual productivity of two commercially important game species, northern bobwhite (Colinus virginianus) and white-tailed deer (Odocoileus virginianus) will most likely be reduced. With birds, short-distance migrants are predicted to be more responsive, and hence adaptable to climate change than long-distance migrants. Because they presently exist on the knife-edge of their physiological tolerance, northern bobwhites may experience severe and widespread population declines in South Texas if a 4ºC (7.2 ºF) increase in average temperature is realized. Whether bobwhites could mitigate this potential problem by shifting their geographic range northward is unknown. The secondary effects of global warming, such as increased or prolonged drought and more intense hurricanes, represent a challenge when it comes to predicting the effects of such events on wildlife. While some wildlife species such as white-tailed deer have the mobility to avoid catastrophic weather events, others do not. Even within-species responses may vary, as indicated by bobwhite response to a recent hurricane in South Texas where adults survived at high numbers but most pre-flight juveniles perished. Even with the potential problems that may be faced by bobwhites and white-tailed deer, wildlife populations in South Texas …