Warming extinguishing lizards

The worst-case scenario of the consequences of global warming - mass extinctions - appears to be a reality for lizards, according to a new report in Science. The authors found that 12 percent of local populations of lizards have already disappeared from hundreds of sites in Mexico. Furthermore, within the next 70 years, the authors predict that 1 in 5 lizard species will no longer exist anywhere on the planet, all the result of rising global temperatures.Sceloporus occidentalisImage: Wikimedia

Written byLauren Urban

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The worst-case scenario of the consequences of global warming - mass extinctions - appears to be a reality for lizards, according to a new report in Science. The authors found that 12 percent of local populations of lizards have already disappeared from hundreds of sites in Mexico. Furthermore, within the next 70 years, the authors predict that 1 in 5 lizard species will no longer exist anywhere on the planet, all the result of rising global temperatures.

Sceloporus occidentalis
Image: Wikimedia commons,
Pierre Fidenci

Although a growing amount of data is showing the impact of climate change on species, these lizard extinctions were somewhat surprising, said linkurl:Jack Sites,;https://lifesciences.byu.edu/DirectoriesInformation/Directories/FacultyStaff/tabid/166/ctl/FacultyProfile/mid/2944/FacultyID/66/Default.aspx an evolutionary geneticist from Brigham Young University, and last author on the paper. "I had always presumed that lizards would be able to adapt to climate change by simply altering their behavior," he said. "However, this is not the case." Rather, the changes in local temperatures are occurring too quickly for evolution to keep pace, he said. "So we have extinctions instead." The study began when the authors returned to 200 sites in Mexico that were home to 48 species of Sceloporus lizards, which had already been sampled in 1975 and 1999. They saw that 12 percent of lizards in the Mexican study area were already locally extinct -- meaning, environmental stressors had eliminated the populations in these particular areas. This alarming rate of extinction prompted first author linkurl:Barry Sinervo,;https://bio.research.ucsc.edu/~barrylab/ a herptologist at the University of California, Santa Cruz, and his colleagues, to dig more deeply into the impacts of climate change on lizards. Lizards regulate their body heat by basking in the sun; too hot, and they retreat to shade. Too much time in the shade, however, and they become unable to gather enough food to grow and survive. The close to 30 co-authors compared the rate of change in lizard populations since the 1970s to historic changes in temperature, and, along with an understanding of lizard physiology and geographic distribution, developed a model to predict how many species would go extinct worldwide, based on how global temperatures are predicted to rise through 2080. The authors then confirmed the model's predictions by comparing them to actual extinction data. "I think the paper is really impressive. It uses historical records of climate variation and population distributions to develop a predictive model. Importantly, it takes past climate variation at face value, without trying to link it to anthropocentric causation," said linkurl:Henry John-Adler,;https://animalsciences.rutgers.edu/faculty/john-alder/henry-john-alder.html an ecologist at Rutgers University, who did not participate in the research. Lizards that were limited to higher elevations by ecological niches are more likely to go extinct, the data suggested, while lizards at lower (and hotter) elevations may be able to survive by moving into those higher, now hotter, elevations. linkurl:Aaron Bauer,;https://www.villanova.edu/artsci/biology/facstaff.htm?mail=aaron.bauer@villanova.edu a systematic herpetologist at Villanova University and co-author, said that extinctions are likely to be "spotty," but each extinction could cause a "cascade of effects both upwards and downwards in the food chain." For instance, a lack of lizards may affect the control of insect disease vectors, or food supply for many birds and small mammals. The paper invokes mechanisms like thermal physiology and ecological mechanisms such as competition to explain how climate change can lead to local extinctions, said John-Adler. "This is an excellent example of the importance of knowing 'how animals work' in order to understand how climate change may affect the diversity and distribution of species." The research is "solid," said linkurl:Laurie Vitt,;https://zoology.ou.edu/Vitt.htm an ecologist and herpetologist at University of Oklahoma. "The outlook for lizard populations around the world [is] very grim indeed." B. Sinervo et al., "Erosion of lizard diversity by climate change and altered thermal nichese," Science:328:894-9, 2010.
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