An international study published in April of 2022 (Cox et al.) has found that 21 percent of the reptile species on Earth (one in five species), amounting to a total of about 2,000 species, are threatened with extinction. The authors estimate that there are more than 12,000 species of reptiles in the world.
To the left are: The Yellow-blotched Map Turtle is considered a vulnerable species by the IUCN.
The Florida Sand Skink is listed as vulnerable by the IUCN.
The False Gharial (Tomistoma schlegelii) is listed as Endangered by the IUCN.
The study shows 30% of forest-dwelling reptiles and about 14 percent of those living in arid areas are threatened, and that 58 percent of all turtle species and 50 percent of all crocodile species are in danger of becoming extinct. The researchers sadly point out that if all the 1,829 species of turtles, crocodiles, lizards, and snakes that have been found to be threatened do indeed become extinct in the coming years, the world will lose a cumulative wealth of 15.6 billion years of evolution.
The comprehensive study is the first of its kind in history. It was conducted by the International Union for Conservation of Nature (IUCN) and included 52 researchers from around the world. The study was published in the prestigious journal Nature.
The IUCN is an international body whose role is, among other things, to assess the threat of extinction posed to various species. Each species of animal or plant receives a score on a five-point scale. The purpose of this ranking is to define those species that are the most endangered, thereby enabling decision makers and various bodies to outline policies accordingly.
The IUCN has been working on the reptile report for the past 18 years, having invited experts on this taxonomic group from all over the world to participate. In 2004, the IUCN released a comprehensive review of the state of reptiles in the world. Reptiles are worse off than that of birds and mammals, although they are not as bad as amphibians. Turtles are threatened more than lizards and snakes, but that may be because we know more about turtles. Perhaps if we knew more about squamata, we would see that they, too, are in serious trouble.
The biggest threat to reptiles is the destruction of their habitats due to agriculture, deforestation, and urban development, and less because of direct hunting, which mainly affects turtles and crocodiles. The authors created detailed maps of these threats. For example, if a particular species is highly threatened in the Sonoran Desert, but not in the rest of its range that may span the entire North American then its not considered a threatened species globally. The new assessments, for more than 10,000 species of reptiles, will allow us to understand their conservation needs, and hopefully enable us to find far more intelligent solutions for them than we have been able to so far.
This study is not the end of the story. We still lack a lot of information about the various risks facing reptiles. For example, climate change is expected to have significant effects on reptiles. The current assessment does not yet include these future threats in its reptile risk assessments. Much work remains to solve the biodiversity crisis.
Cox N, Young BE, Bowles P, Fernandez M, Marin J, Rapacciuolo G, Böhm M, Brooks TM, Hedges SB, Hilton-Taylor C, Hoffmann M. 2022. A global reptile assessment highlights shared conservation needs of tetrapods. Nature. 2022 May;605(7909):285-90.
Turtles and Crocodilians are the most endangered reptiles. However, many squamates are also endangered.
Amphibians are tetrapods and all frogs, and most salamanders have four limbs, but there are exceptions; and caecilians lack limbs completely. Extant amphibians have representatives present in virtually all terrestrial and freshwater habitats, but are absent from the coldest and driest regions, and from most remote oceanic islands. The number of recognized species of amphibians has grown enormously in recent years, The unprecedented growth largely in species reflects an increase in collecting work in previously remote locations, a significant growth of active herpetological communities in a few megadiverse countries, and the application of complementary techniques, such as molecular genetics, to support more traditional taxonomic methods. Even countries such as Sri Lanka, in which biodiversity inventories were deemed to be relatively complete are revealing startling levels of previously undocumented and unsuspected diversity. Unfortunately, the rapid increase in the knowledge of amphibian species, diversity, and biology is coincident with a massive global decline in amphibian populations.
To the left is a pair of Golden Toads I (JCM) photographed in 1986. The species is now thought to be extinct.
Habitat loss is the primary threat to amphibians globally. Sixty-three percent of species are affected, of which almost nine out of every 10 species (87%) are threatened with extinction. The figures for threatened amphibians are comparable with those for threatened birds, where habitat loss and degradation affect 86% of species. Seventy-five percent of amphibians inhabit tropical forest environments – the same habitats that are subject to the highest rates of forest loss. Habitat loss is mostly the result of clearance for agriculture, followed by extraction activities, like logging and mining. Urbanization and industrial development are also major contributors to habitat loss. Habitat fragmentation (decreasing patch size) and increasing isolation of patches results in an increased risk of events that increase risk of extinction. Connections between patches are important in the viability of amphibian populations mostly through juvenile dispersal.
Cox N, Young BE, Bowles P, Fernandez M, Marin J, Rapacciuolo G, Böhm M, Brooks TM, Hedges SB, Hilton-Taylor C, Hoffmann M. A global reptile assessment highlights shared conservation needs of tetrapods. Nature. 2022 May;605(7909):285-90.