Elucidating mechanisms underlying amphibian declines in North America using hierarchical spatial models

Amphibian populations are declining globally at unprecedented rates but statistically rigorous identification of mechanisms is lacking. Identification of reasons underlying large-scale declines is imperative to plan and implement effective conservation efforts. Most research on amphibian population decline has focused on local populations and local factors. However, the ubiquity of declines across species and landscapes suggests that causal factors at a broader scale are also important. Elucidation of the mechanisms driving population change has lagged, mainly because data have been unavailable at continental scales. We propose to address this need by assembling data to answer questions about broad-scale drivers of amphibian decline. We will examine alterations in timing and availability of surface-water habitat (driven principally by climate change), as first order variables that control the probabilities of breeding, successful metamorphosis, and return rates of amphibians. Climate change (and its influence on shifting temperatures) is also correlated with other agents of decline such as disease and amplification of cyclical population dynamics; we consider these second-order effects. Furthermore, data on other causal mechanisms are not available at broad-scales. We will use monitoring data (core data from USGS Amphibian Research and Monitoring Initiative, supplemented by data from collaborators in Canada, the U.S., and Mexico) and state-of-the-art statistical techniques to examine broad-scale mechanisms associated with changes in amphibian occupancy. We will develop hypotheses for climate-induced shifts in occupancy dynamics, and test these hypotheses using a dataset representing many individual projects and regions from across North America. We will formulate the problem in hierarchical Bayesian models to examine multi-scale processes affecting patterns of species occupancy. This analysis of population trends across multiple spatial scales will facilitate the first rigorous quantitative examination of mechanisms affecting occupancy of amphibians across North America, and provide a continent-wide assessment of the contribution of climate-related factors to declines in amphibian populations. Hypotheses and methods developed through this collaborative effort will be useful in other locations experiencing amphibian declines (e.g., Australia, Europe) and our modeling approach will be useful for assessments of other taxa.







Publication(s):

Amburgey, S.M., Miller, D.A.W., Campbell Grant E.H., Rittenhouse, T.A.g., Benard, M.F., Richardson, J.L., Urban, M.C., Hughson, W., Brand, A.B., Davis, C.J., Hardin, C.R., Paton, P.W.C., Raithel, C.J., Relya, R.A., Scott, A.F., Skelly, D.K., Skidds, D.E., Smith, C.K., and Werner, E.E. (2017) “Range position and climate sensitivity: The structure of among-population demographic responses to climatic variation.” Glob Change Biol. 00:1-16. doi:10.1111/gcb.13817



Grant, E. H. C., Miller, D. A. W., Schmidt, B. R., Adams, M. J., Amburgey, S. M., Chambert, T. Cruickshank,S.S. Fisher R.N., Green, D.M., Hossack, B.R., Johnson, P.T.J., Joseph, M.B., Rittenhouse, T.A.G., Ryan, M.E., Hardin Waddle, J., Walls, S.C., Bailey, L.L., Fellers, G.M., Gorman, T.A., Ray, A.M., Pilliod, D.S., Price, S.J., Saenz, D., Sadinski, W., and Muths, E. (2016). Quantitative evidence for the effects of multiple drivers on continental-scale amphibian declines. Scientific Reports, 6, 25625. http://doi.org/10.1038/srep25625



Muths, E., & Fisher, R. N. (2015). An alternative framework for responding to the amphibian crisis. Oryx, 1-4. http://doi.org/10.1017/S0030605315001131



Miller, D.A.W., Campbell Grant, E.H., Muths., Amburgey, S.M., Michael J. Adams, Maxwell B. Joseph, J. Hardin Waddle, Pieter T. J. Johnson, Maureen E. Ryan, Benedikt R. Schmidt, Daniel L. Calhoun, Courtney L. Davis, Robert N. Fisher, David M. Green, Blake R. Hossack, Tracy A. G. Rittenhouse, Susan C. Walls, Larissa L. Bailey, Sam S. Cruickshank, Gary M. Fellers, Thomas A. Gorman, Carola A. Haas, Ward Hughson, David S. Pilliod, Steven J. Price, Andrew M. Ray, Walt Sadinski, Daniel Saenz, William J. Barichivich, Adrianne Brand, Cheryl S. Brehme, Rosi Dagit, Katy S. Delaney, Brad M. Glorioso, Lee B. Kats, Patrick M. Kleeman, Christopher A. Pearl, Carlton J. Rochester, Seth P. D. Riley, Mark Roth & Brent H. Sigafus  “Quantifying Climate Sensitivity and Climate-Driven Change in North American Amphibian Communities.” Nature Communications 9, no. 1 (September 25, 2018): 3926. https://doi.org/10.1038/s41467-018-06157-6.