Global Amphibian and Reptile Decline

Collectively, amphibians and reptiles are the most threatened vertebrate group on Earth. According to the International Union for Conservation of Nature (IUCN), as of 2008, 42% of amphibian species showed evidence of decline, and 32% were globally threatened (Critically Endangered, Endangered or Vulnerable categories) or extinct (IUCN amphibian assessment). Moreover, 38 species have gone extinct and an additional 120 species are likely extinct. By November 2016, the IUCN had evaluated 6,492 of the 7,500 amphibian species currently recognized by amphibiaweb.org, with decline percentages remaining unchanged. Reptiles (10,450 species recognized as of August 2016 on reptile-database.org) are not doing much better: based on evaluation of a random representative sample of 1,500 species, a 2013 study estimated 19% of all reptiles are threatened with extinction (Monika et al. 2013). Through additional field sampling and utilizing new DNA techniques, previously undiscovered (or unrecognized) species of amphibians and reptiles are being described every year. Since 1985, the total number of recognized amphibian species has increased by over 60%. While this increase in our knowledge of species diversity is exciting, the fact that many of these species are already threatened with extinction when discovered strongly suggests that others may have disappeared before we even knew they existed.

Status of Amphibians and Reptiles in Canada

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the conservation status of species in Canada. COSEWIC is comprised of university professors, government and non-government biologists, and other individuals with relevant expertise, and their assessments are based on the best available scientific information, community knowledge and Aboriginal Traditional Knowledge. Species that are at some risk of disappearing from Canada are identified as Endangered, Threatened or Special Concern (in descending order of extinction risk). Species that no longer occur in the wild in Canada are identified as Extirpated, and those that no longer occur in the wild anywhere in the world are listed as Extinct. Species that are secure are identified as Not at Risk. A species may also be identified as Data Deficient if there is not enough information to assess its status. The COSEWIC status assessments inform Schedule 1 of Canada’s Species at Risk Act (SARA), which is the official list of species at risk in Canada. However, there is often a significant lag time between the COSEWIC assessment and the update to the species’ status on Schedule 1 under the SARA. In rare instances, the Minister of the Environment may delay updates to Schedule 1 indefinitely if there is concern that the species listing will have significant socio-economic repercussions (e.g., species that are a commercial resource).

Sadly, the status of amphibian and reptile species is even worse in Canada than it is globally, particularly for reptiles. As of December 2016, 44% (23/52) of amphibian species and subspecies and 65% (33/51) of reptile species and subspecies have been listed as Endangered, Threatened or Special Concern by COSEWIC. The extremely high number of reptile species at risk makes this the most endangered group of animals in Canada. Additionally, several species have been extirpated from the country: the Timber Rattlesnake, Eastern Box Turtle, Blanchard’s Cricket Frog, Pygmy Short-horned Lizard and Pacific Pond Turtle. Other species have disappeared from large portions of their former ranges, particularly in highly developed areas of southern Ontario and British Columbia. For example, the Massasauga rattlesnake, Blanding’s Turtle and Jefferson Salamander have all vanished from much of their historical range in southern Ontario, while the Northern Leopard Frog, Western Painted Turtle and Western Rattlesnake have been lost from many previously inhabited areas in western Canada. Many amphibian and reptile species also have naturally small distributions in Canada because they are at the northernmost limit of their range. Most of these species, such as the Blue Racer, Allegheny Mountain Dusky Salamander and Sharp-tailed Snake, are highly endangered in Canada because their already-small populations are limited to the most developed regions in the country where habitat loss, road development and other threats are most severe.

The major threats that are responsible for historic and ongoing amphibian and reptile declines in Canada include habitat loss and fragmentation, road mortality, chemical contamination and other environmental pollution, infectious disease, invasive species, climate change, illegal collection and intentional persecution.

At the 7th World Congress of Herpetology held in 2012 in Vancouver, Canadian researchers convened for the symposium “Canadian Herpetofauna: What are the threats.” The resulting multi-authored synthesis—“Conservation of herpetofauna in northern landscapes: Threats and challenges from a Canadian perspective”—was published in the journal Biological Conservation in 2014, and provides a good summary of the history and current situation regarding amphibian and reptile declines in Canada and the tools in place to address them.

Further reading:

Böhm, Monika et al. 2013. The conservation status of the world’s reptiles. Biological Conservation 157: 372-385.

Gibbons, J.W., D.E. Scott, T.J. Ryan, K.A. Buhlmann, T.D. Tuberville, B.S. Metts, J.L. Greene, T.Mills, Y. Leiden, S. Poppy and C.T. Winne. 2000. The Global Decline of Reptiles, Déjà Vu Amphibians. BioScience 50: 653-666.

Houlahan, J.E., C.S. Findlay, B.R. Schmidt, A.H. Meyer and S.L. Kuzmin. 2000. Quantitative evidence for global amphibian population declines. Nature 404: 752-755.

Lesbarrères, David, S.L. Ashpole, C.A. Bishop, G. Blouin-Demers, R.J. Brooks, P. Echaubard, Purnima Govindarajulu, D.M. Green, S.J. Hecnar, Tom Herman, J. Houlahan, J.D. Litzgus, M.J. Mazerolle, C.A. Paszkowski, P. Rutherford, D.M. Schock, K.B. Storey and S.C. Lougheed. 2014. Conservation of herpetofauna in northern landscapes: Threats and challenges from a Canadian perspective. Biological Conservation 170: 48-55. doi: 10.1016/j.biocon.2013.12.030