A new study warns that more than a fifth of all reptile (爬行动物) species are threatened with extinction, which may have a bad impact on the planet.

The largest ever analysis of the state of the world's reptiles, published in Nature, has showed that 21% of the reptile species are facing extinction. The study says from lizards to snakes, such a loss could have disastrous impacts on ecosystems around the world.

Although many reptiles live in dry environments such as deserts, most species occur in forests, where they suffer from threats such as logging of land for agriculture. 30% of the forest-dwelling reptiles are at risk of extinction, compared with 14% in dry habitats. Hunting is also a major threat to reptiles, especially turtles and crocodiles, many of which are at risk of extinction. Another major contributing factor is the introduction of invasive species.

"If we removed reptiles, it could change ecosystems fundamentally, with unfortunate knock-on effects, such as increases in pest insects," said Neil Cox, co-leader of the study. "Biodiversity, including reptiles, supports the ecosystem services that provide a healthy environment for people."

Our hope is that this first-ever assessment of the world's 10,000-plus reptiles helps put them in the spotlight and goes some way to highlighting this diversity, and just how much we have to lose. As well as controlling rats, mosquitoes and other pests, reptiles deliver many other benefits. "They help spread seeds, especially in island environments," said researcher Hoffmann. "We've also achieved many medical advances from studies of reptiles."

The results of the study are not all doom and gloom. Scientists have found, surprisingly, that if they set out to protect places where threatened birds, mammals and amphibians (两栖动物) live together, they'll meanwhile protect many more threatened reptiles.