London: A fifth of the world`s reptiles are estimated to be threatened with extinction, scientists have warned.
Out of the 19 per cent reptiles close to extinction, 12 per cent classified as Critically Endangered, 41 per cent Endangered and 47 per cent Vulnerable.
More than 200 world renowned experts assessed the extinction risk of 1,500 randomly selected reptiles from across the globe, according to a paper published by the Zoological Society of London (ZSL) in conjunction with experts from the IUCN Species Survival Commission (SSC).
Extinction risk is not evenly spread throughout this highly diverse group - freshwater turtles are at particularly high risk, mirroring greater levels of threat in freshwater biodiversity around the world.
Overall, this study estimated 30 per cent of freshwater reptiles to be close to extinction, which rises to 50 per cent when considering freshwater turtles alone, as they are also affected by national and international trade.
Although threat remains lower in terrestrial reptiles, the often restricted ranges, specific biological and environmental requirements, and low mobility make them particularly susceptible to human pressures.
The study is the first of its kind summarising the global conservation status of reptiles, in the journal of Biological Conservation.
Three Critically Endangered species were also highlighted as possibly extinct. One of these, a jungle runner lizard Ameiva vittata, has only ever been recorded in one part of Bolivia.
Levels of threat remain particularly high in tropical regions, mainly as a result of habitat conversion for agriculture and logging. With the lizard`s habitat virtually destroyed, two recent searches for the species have been unsuccessful.
"Reptiles are often associated with extreme habitats and tough environmental conditions, so it is easy to assume that they will be fine in our changing world," Dr Monika Bohm, lead author on the paper, said.
"However, many species are very highly specialised in terms of habitat use and the climatic conditions they require for day to day functioning. This makes them particularly sensitive to environmental changes," Bohm added.
In Haiti, six of the nine species of Anolis lizard included in this study have an elevated risk of extinction, due to extensive deforestation affecting the country.
Collectively referred to as `reptiles`, snakes, lizards, amphisbaenians, crocodiles, and tuataras have had a long and complex evolutionary history, having first appeared on the planet around 300 million years ago.
They play a number of vital roles in the proper functioning of the world`s ecosystems, as predator as well as prey.