Almost one in five reptiles is facing extinction, experts have warned .
The first global assessment of its kind of reptile species, which include crocodiles, lizards, snakes, tortoises and turtles, estimated that 19% of them are struggling to survive.
Of those under threat, 12% are considered to be critically endangered, meaning they are at the highest risk of extinction, while 41% are endangered and 47% vulnerable to going extinct, the study in the journal Conservation Biology said.
The biggest threats to reptiles are man-made habitat loss, for example from agriculture or logging, and being harvested by people, said the Zoological Society of London (ZSL) and the International Union for Conservation of Nature (IUCN). Other problems such as urban development and invasive species are also threatening reptiles.
Philip Bowles, from the IUCN Species Survival Commission, said: "The findings sound alarm bells about the state of these species and the growing threats they face. Tackling the identified threats, which include habitat loss and over-harvesting, are key conservation priorities in order to reverse the declines in these reptiles."
Reptiles in freshwater habitats, the tropics and ocean islands are under greatest threat, with 30% of freshwater species estimated to be facing extinction. The study warned that half of all freshwater turtles, which are threatened by national and international trade as well as threats to their habitat, are at risk of dying out.
Although land reptiles are at a lower risk, species are often restricted to specific places or habitats and have low mobility, making them susceptible to human pressures.
In Haiti, six of the nine species of Anolis lizard are at a higher risk of extinction because of widespread deforestation on the island. The report also highlighted that three critically endangered species of lizard may be extinct, including a jungle runner lizard, Ameiva vittata, which has only ever been recorded in one part of Bolivia. The lizard's habitat has been virtually destroyed, and two recent searches for the species were unsuccessful, the experts said.
Dr Monika Bohm, lead author of the scientific paper, said: "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. However, many species are 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."
The study by 200 experts around the world assessed the risk of extinction of almost 1,500 randomly selected reptile species around the world. There are known to be more than 9,000 species of reptile on Earth, first appearing around 300 million years ago. Experts said they play vital roles in ecosystems, as both predators and prey.