During the past 4 years (2013-2017) we investigated ongoing extirpations of reptiles and amphibians across six continents. Extirpations are extinctions of local populations. If extirpations at multiple sites of known occupancy continue unabated and throughout the geographic range of a species, then this ultimately results in the total extinction of a species. Thus, we assembled data on the current impacts of climate warming and droughts on amphibians and reptiles due to the increase in atmospheric carbon dioxide from 1975-present. We also collected data on physiology of reptiles and amphibians, as well as tree habitats where they are found, at hundreds of sites on 6 continents (North America, South America, Europe, Africa, Asia, Australia), with over 70 international collaborators in 24 countries (Argentina, Australia, Brazil, Bolivia, Canada, Chile, China, Colombia, Congo, Costa Rica, Ecuador, Finland, France, Germany, Greece, India, Indonesia, Italy, Mexico, Namibia, Peru, South Africa, Spain, Uruguay, USA).

We study the physiology of trees to understand how drought stress induced by climate change on trees might affect tree die-off events. As trees die, the local temperatures dramatically increase (the shade provided by trees is reduced and change in albedo), which can accelerate ongoing population declines and many more extirpations of reptiles and amphibians. We also use satellite imagery to map tree and vegetation die-offs at very large spatial scales and then use the data from the satellites to estimate local warming of the surface of the earth, where the reptiles and amphibians are found. 

Global surveys completed by Sinervo and Miles (as well as international collaborators) led to the discovery of 201 extirpations of reptiles. We are using these data on observed extirpations to develop models that more accurately forecast future extinctions due to climate warming. We have also assembled data on thousands of local extirpations recorded in the published literature for amphibians. Our models include new data that we have collected on the measured physiological limits on thermoregulation from present-day animals. We have used the observed current extirpations merged to this data on physiology to compute how physiological limits have been already been exceeded in the present day to more accurately project future extinctions. 

Our models project that species-level extinctions of lizards and amphibians due to future warming will be similar and will vary between 30-50% of current species, depending on geographic area and taxon. We also predict that entire families of these two vertebrate groups will go extinct by 2070, the hallmark of a mass extinction event. During the history of our planet, going back in time 520 million years, we have only seen 5 major extinction events of this magnitude. Future climate model scenarios in which we adopt aggressive strategies to limit carbon dioxide production will limit warming and the number of total species going extinct will be greatly reduced to 5-10%.

We also have used our models to reconstruct the ancient ranges of several species of reptiles including tortoise and lizard species, by fitting our physiological models to the paleoclimate data produced by climate scientists. These models indicate that animals experiencing climate change in the present day will have to move (disperse to new sites) at rates 100 to 1000 times faster than under any paleoclimate scenario (e.g., geologic period in the past). Thus, it is impossible for most reptiles and amphibians to move at these rates under the current rate of warming and we may have to use assisted migration to move them to places where they will have refuges from future warming.

Broader Impacts. During our NSF project we developed mathematical models that provide biological resource managers the necessary tools for identifying critical habitat in existing national parks and reserves as well as establishing new reserves and parks where refugia are available for preserving amphibians and reptiles populations from deleterious consequences of climate warming. Such capabilities are critical, because boundaries of established parks are static, but the habitat necessary to support amphibian and reptile populations are likely to be shifted poleward or higher in elevation. For example, many suitable habitats are predicted to be located in montane, forested zones. During our project, we also trained over 440 researchers (faculty, postdoctoral fellows and graduate students) during 25 workshops we carried out in the countries of our collaborators. We also directly trained 10 graduate students and 6 postdoctoral fellows in our laboratories. We also trained 14 students that visited our laboratories in the US from the laboratories of our international collaborators. 

Last Modified: 03/16/2018
Modified by: Barry R Sinervo