What Climate Change Means for Reptiles

Anthropogenic climate change is one of the major threats to biodiversity conservation in the 21st century. While its consequences are global, some species, or taxonomic groups, may be more at risk than others.

For instance, (non-avian) reptiles may be at higher extinction risk due to climate change than birds and mammals. First, reptiles are cold-blooded animals, which means that they rely on external temperatures and cannot generate their own body heat. This makes it harder for them to extend or stretch out their habitats, or even to adjust to rapid temperature changes1. Therefore, they will be less resilient to the environmental changes associated with climate change, including harsher weather and temperatures.

Second, while sex is determined genetically at conception in many vertebrates, offspring sex in many reptiles is determined by environmental temperatures during the period of embryonal development, and thus during egg incubation2. Since even modest increases in mean temperature (<2°C) may skew the offspring sex ratio, the issue of climate change, which may see temperature increases of 1.5°C (compared to pre-industrial levels) or more by 2030, can severely threaten the conservation of entire reptile populations.

This issue is already significant in some parts of the world. For example, it appears that in Raine Island, Australia, shifting temperatures meant that the local population of pacific green sea turtles has produced almost exclusively female offspring in the last 20 years3.

Furthermore, since turtles tend to be philopatric – and thus tend to instinctively return to their natal grounds to lay their eggs4 – it may be further difficult for them to escape the trap of climate change and find cooler beaches where to lay eggs.

Similarly, habitat fragmentation is a major influencing factor on whether non-marine reptiles with temperature-dependent sex determination will persist through climate change. While reptiles may be already poorly predisposed to habitat shifts (see above), habitat fragmentation and degradation also means that many reptile species are isolated in pockets of land, unable to find new, suitable habitat5.

As many as 20% of reptile species could be extinct by 20801.

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References

  1. Rolland, J., Silvestro, D., Schluter, D., Guisan, A., Broennimann, O. and Salamin, N., 2018. The impact of endothermy on the climatic niche evolution and the distribution of vertebrate diversity. Nature ecology & evolution2(3), p.459.
  2. Janzen, F.J., 1994. Climate change and temperature-dependent sex determination in reptiles. Proceedings of the National Academy of Sciences91(16), pp.7487-7490.
  3. https://www.nationalgeographic.com/news/2018/01/australia-green-sea-turtles-turning-female-climate-change-raine-island-sex-temperature/
  4. FitzSimmons, N.N., Limpus, C.J., Norman, J.A., Goldizen, A.R., Miller, J.D. and Moritz, C., 1997. Philopatry of male marine turtles inferred from mitochondrial DNA markers. Proceedings of the National Academy of Sciences94(16), pp.8912-8917.
  5. Driscoll, Don A. “Extinction and outbreaks accompany fragmentation of a reptile community.” Ecological Applications 14, no. 1 (2004): 220-240.

featured image credits: https://bit.ly/2pW2ZjV

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