Reptiles are among the oldest animals on the planet, yet the future looks uncertain for these iconic cold-blooded species after a new study revealed that 21 percent are now threatened with extinction. Of the 10,196 reptile species included in the analysis, 1,829 were found to be vulnerable, endangered, or critically endangered.

Writing in the journal Nature, the study authors explain that 40.7 percent of amphibians, 25.4 percent of mammals, and 13.6 percent of birds are currently threatened with extinction, but that the risk to reptiles has been largely overlooked by previous analyses. Commenting on this lack of representation, study author Dr Bruce Young explained to the BBC that “reptiles to many people are not charismatic and there's been a lot more focus on more furry, feathery species of vertebrates for conservation.”

To fill this knowledge gap, the researchers spent 15 years conducting the first comprehensive extinction-risk assessment for reptile species across the globe. Findings indicate that 57.9 percent of turtles and 50 percent of crocodiles are now under threat, along with 19.6 percent of squamates – an order of reptiles that includes lizards and snakes.

Within squamates, a staggering 73.8 percent of iguanids are at risk of becoming extinct. Overall, forest-dwelling reptiles were found to be under greater threat than those inhabiting arid landscapes, with agriculture, logging, and urban development the main causes of reptilian peril.

“Among the conservation strategies needed to prevent reptile extinction, land protection is critically important to buffer many threatened species from the dual threats of agricultural activities and urban development,” write the authors. “Furthermore, introduced mammals to islands threaten 257 reptile species (2.8% of all reptiles), calling for continued campaigns to eradicate introduced mammals in those places.”

The researchers also highlight the threat posed by the pet trade to turtles, while crocodile numbers are impacted by hunting. Unsurprisingly, climate change also has a role to play in reptiles’ fortunes, as thermally viable windows for foraging become shortened and sex ratios become skewed in species that have temperature-dependent sex determination.

While such existential threats loom over reptiles worldwide, those living in southeast Asia, West Africa, northern Madagascar, the northern Andes, and the Caribbean currently face the highest level of risk.

According to the researchers, conservation efforts aimed at protecting endangered mammals, birds, and amphibians are likely to benefit reptiles that share their habitat with these species. However, they also point out that 31 threatened reptiles occupy ranges that don’t overlap with any other endangered animals, highlighting the need for “urgent, targeted action” to protect these vulnerable creatures.

Bringing home the severity of the situation, the authors reveal that should all of the threatened reptile species become extinct, a combined 15.6 billion years of genetic diversification would be forever erased from the planet.