Assessing Wildfire Impacts on Canopy Density and the Extinction Risk of Amphibians

Abstract:

Canopy density affects amphibian thermoregulation, as they face a fundamental tradeoff between maintaining activity at higher temperatures and increased rate of water loss. Increased wildfires will impact canopy density, and therefore, the thermoregulation and extinction risk of amphibians at breeding ponds. In this study, we measure the effect of canopy coverage on the thermoregulation of the California Red-legged Frog, Rana draytonii. We use agar models with temperature probes to measure the thermal and hydric capacities of frogs in different microclimates and canopy densities at a breeding pond. By generating functions to represent the hours a species is restricted from activity due to climate changes, we predict extinction risk by creating present and future species distribution models. We further expand these models to add the impacts that increasing wildfires will have on amphibian extinction via changes in canopy density. We find that canopy density has a significant influence on environmental temperature and rates of evaporation, and that thinner density provides a more optimal environment for amphibian thermoregulation. Differences in canopy density, both natural and from wildfires, also severely alter the extinction risk probability of a R. draytonii population. Our models show that we must not only include thermal and hydric climate changes, but also large-scale ecosystem disturbances, like increased wildfires, to understand amphibian extinction risk.