Some Like It Hot: Effects of Forest Clearing on Nest Temperatures of Montane Reptiles

Global climate change may affect the upper elevational limits of distribution of montane organisms, especially if those limits are set directly by temperature. Oviparous (egg-laying) reptiles are constrained in this way because of their nesting requirements. In many areas, deforestation has already subjected these animals to small-scale “climate change.” Clearing for power lines (hydrocuts) increases solar radiation to potential nest sites, and hence enables these animals to penetrate higher into montane areas than would otherwise be possible. Such small-scale anthropogenic “warming” may offer a useful model system to explore consequences of broader climate change on the distribution and biology of montane organisms. We quantified thermal effects of a hydrocut in montane eucalypt forest in the Brindabella Range of southeastern Australia. The reduced canopy cover, increased duration of sunlight exposure, and higher levels of incident radiation in cleared areas substantially modified thermal regimes in potential nest sites. Orientation and exposure were the most important determinants of nest temperature and predicted the distribution of natural nests. Such cleared corridors (for roads, power lines, ski runs, etc.) may not only extend the upper elevational limit for oviparous reptiles, but may also modify the genetic structure and demography of populations.