Hydroperiod variability constrains populations of amphibians dependent on ephemeral wetlands in projected climate simulations

Background/Question/Methods

Amphibian populations are threatened globally by multiple potential stressors habitat availability and exposure to contaminants. Changing weather patterns can alter hydroregimes (duration, frequency, timing, and depth of water) in ephemeral wetlands that many amphibian species require for breeding and successful recruitment. Determining the population-level impacts of pesticide exposure is further complicated in species with biphasic life cycle and both aquatic and terrestrial resource needs. Ecological risk assessment of amphibians ideally should encompass the appropriate spatial and temporal scale to adequately capture influential ecological processes and demographic responses. To demonstrate the importance of representing environmental stochasticity in population assessments, a climate change projection identifying suitable breeding habitat was used to simulate population dynamics for southern toad (Anaxyrus terrestris) populations, including possible scenarios of breeding habitat availability. These impacts include both probabilistic and projected estimation of complete reproductive failure in years with unsuitable breeding habitat as well as reduced larval survival resulting from pesticide exposure.

Results/Conclusions

In our models, populations were negatively impacted by long periods of drought and consequently multiple sequential years of reproductive failure. These results emphasize the necessity of reliable climate projections to accurately represent the effects of reduced breeding habitat availability on amphibian populations. Flexible modifications to existing risk assessment methods to allow inclusion of various extrinsic stressors and identify demographic and ecological vulnerabilities, could greatly improve existing approaches.