How Climate Change Impacts the Mortality Rate of Latin American Frogs

An Interaction Between Climate Change and Infectious Disease Drove Widespread Amphibian Declines

by: Jeremy M. Cohen, David J. Civitello, Matthew D. Venesky, Taegan A. McMahon, Jason R. Rohr

Summarized by: Kailey McCain

What data were used? 

This study combined laboratory experiments, field data, and climate records together to support their hypothesis that amphibians have a higher mortality (death) rate when exposed to warmer temperatures, this is known as the “thermal mismatch hypothesis”

Methods: 

Atelopus zeteki or the Panamanian Golden Frog in their natural habitat.

The laboratory experiments consisted of a temperature gradient and a temperature shift experiment. Both experiments exposed an endangered captive frog, Atelopus zeteki or the Panamanian Golden Frog, to a disease causing fungus, Batrachochytrium dendrobatidis, and measured the rate of death. The temperature gradient gradient slowly increased the temperature, while the temperature shift experiment exposed the frog to the fungus at specific temperature units: 14°C, 17°C, 23°C, or 26°C.  

The data was then compared to field data collected from the International Union for Conservation of Nature red list database to observe a real time decline in a total of 66 species of frog. The geographical range for the field data was limited to Latin America and the rate of decline was compared to historic monthly climate data.

Results:  

The results of the temperature gradient and temperature shift experiments show that mortality increased when the infected frog was exposed to higher temperatures. However, it also shows that temperature did not affect the mortality rate of the control group, the non infected frogs. As for the field data collected, the results showed that the frogs’ decline could not be correlated to precipitation nor altitude, but climate change, the thermal mismatch hypothesis clearly  predicted an increased decline of the species.

Figure A represents the data collected for the temperature gradient experiment and shows a linear decline in survival time with an increase in temperature. Figure B represents the data collected for the temperature shift experiment and shows the different temperature units plotted by the proportion alive versus time. The graph indicates that the warmest temperature has the lowest survival rate.

Why is this study important? 

This study tackles two of the largest challenges facing the modern world: climate change and disease prevalence. Some believe these issues are falsely linked, but the evidence collected in this study shows a positive correlation between disease induced death and increased temperature, both in a laboratory environment and the outside world. 

The big picture: 

While this study was isolated in geographical terms, the data collected gives researchers a look into what the future might hold for the spread of diseases in a warming world. Alone, the rising temperatures were not found to increase the rate of mortality; however, when mixed with a pathogen, a deadly combination was created and increased the rate of mortality greatly.

Citation: full citation of paper 

Cohen, J. M., Civitello, D. J., Venesky, M. D., McMahon, T. A., & Rohr, J. R. (2019). An interaction between climate change and infectious disease drove widespread amphibian declines. Global Change Biology, 3, 927. https://doi-org.ezproxy.lib.usf.edu/10.1111/gcb.14489

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