Module 8
Conservation & Climate
Reptiles are the second-most-threatened vertebrate class after amphibians: IUCN 2022 reports ~21% of assessed reptile species threatened with extinction. The four dominant drivers are habitat loss, climate warming (amplified by ectothermy and TSD), emerging infectious disease (especially snake fungal disease, Ophidiomyces ophiodiicola), and the pet trade.
1. Sinervo 2010 Extinction Projections
Sinervo 2010 (Science) integrated operative-temperature mapping, behavioural thermoregulation models, and historical extirpation records across 48 lizard populations globally. The key metric is hours of restriction: the fraction of day when Te exceeds the critical thermal maximum forcing the animal into refugia rather than foraging. Populations where restriction exceeds a species-specific threshold suffer negative energy balance, reduced reproduction, and eventual local extinction.
Under IPCC mid-range warming, Sinervo predicted 20% of global lizard species and 39% of populations lost by 2080. The prediction has been broadly confirmed by subsequent tropical Mexico and Madagascar datasets (Diele-Viegas 2020). Tropical species are counter-intuitively more vulnerable than temperate species because they already live close to their CTmax.
Simulation: Latitudinal Extinction Risk
Simple implementation of Sinervo 2010’s logic at tropical, subtropical, and temperate latitudes: as body temperatures drift upward, hours of restriction increase and eventually push local populations past the extinction threshold.
Click Run to execute the Python code
Code will be executed with Python 3 on the server
2. Snake Fungal Disease (Ophidiomycosis)
Ophidiomyces ophiodiicola is a keratin-degrading fungus that produces facial dermatitis, scale disfigurement, and death in North American and European snakes. First described in 2006, detected in 23 US states by 2020, and now confirmed on three continents (Lorch 2016, mBio). Clinical signs include crusting nose-leaf lesions, failed ecdysis, and secondary bacterial infection. Impact on Crotalus horridus (timber rattlesnake) and Sistrurus catenatus (massasauga) is significant; the disease is a leading candidate for listing several US rattlesnakes as federally threatened.
The ecological parallel is amphibian chytridiomycosis (Batrachochytrium dendrobatidis), a fungal pandemic that decimated amphibian faunas worldwide. Ophidiomycosis has not yet reached pandemic proportions but shares enough biological features to warrant urgent surveillance.
3. Sea Turtles & TSD
Six of seven sea-turtle species are IUCN Vulnerable or Endangered. Threats include fisheries bycatch, beach-nest predation (feral pigs, ghost crabs), plastic ingestion, and — as M6 detailed — TSD-driven feminisation under warming. The northern Great Barrier Reef Chelonia mydas rookery is >99% female in juveniles (Jensen 2018); adult sex ratio remains more balanced only because of slow turnover from pre-warming cohorts.
Mitigation options include shading of key nesting beaches, irrigation of nests with seawater to drop mean T by 1–2 °C, and translocation of eggs to cooler rookeries. The last approach risks disrupting natal-site imprinting.
4. Pet Trade & CITES
Reptiles are the most traded vertebrates in the exotic-pet market. Auliya 2016 documented ~30 million reptiles imported to the US and EU in the 2005–2015 decade, many from unmanaged wild harvests. Species disproportionately affected: Madagascan day geckos, Indonesian blue-tongued skinks, South American boa constrictors, Malagasy and Southeast Asian turtles. CITES lists all sea turtles, all crocodilians, ~80% of monitor lizards, most pythons, boas, and chameleons on Appendix I or II.
Illegal trade in reptiles is substantial: a 2021 Janssen & Leupen analysis found >3 400 species traded on online marketplaces, over 80% not covered by CITES or by national harvest quotas.
5. Synthesis of the Course
Reptiles are a biophysically rich clade whose adaptations — scale patterning, ectothermic thermoregulation, limbless locomotion, multimodal sensing, chemically sophisticated venoms, TSD — span nine orders of magnitude in body mass and over 320 million years of evolution. Their biology also makes them disproportionately exposed to current anthropogenic pressures: TSD amplifies climate risk, ectothermy constrains latitudinal migration, keratin-based skin is vulnerable to emerging fungal pathogens, and the same slow life history that lets a tortoise outlive a human makes recovery from population crashes exceptionally slow. Mitigation calls on the full toolkit of modules 0–7: habitat protection, climate action, disease surveillance, breeding programmes, and trade regulation.
Key References
• Sinervo, B. et al. (2010). “Erosion of lizard diversity by climate change and altered thermal niches.” Science, 328, 894–899.
• Diele-Viegas, L. M. & Rocha, C. F. D. (2020). “Climate change effects on reptiles: a systematic review.” Clim. Change, 160, 17–34.
• Lorch, J. M. et al. (2016). “Snake fungal disease: an emerging threat to wild snakes.” Phil. Trans. R. Soc. B, 371, 20150457.
• Jensen, M. P. et al. (2018). “Environmental warming and feminization of one of the largest sea turtle populations in the world.” Curr. Biol., 28, 154–159.
• Auliya, M. et al. (2016). “Trade in live reptiles, its impact on wild populations, and the role of the European market.” Biol. Conserv., 204, 103–119.
• Janssen, J. & Leupen, B. T. C. (2019). “Traded under the radar: a review of the use of online platforms for the wildlife trade.” TRAFFIC Bulletin, 31, 23–31.
• Böhm, M. et al. (2013). “The conservation status of the world’s reptiles.” Biol. Conserv., 157, 372–385.
• Cox, N. et al. (2022). “A global reptile assessment highlights shared conservation needs of tetrapods.” Nature, 605, 285–290.