About 20 percent of reptile species risk extinction, mainly because people are taking away their habitats for agriculture, urban development and logging, according to the first global reptile assessment of its kind.
From inch-long geckos to the iconic king cobra, at least 1,829 species of reptiles, including lizards, snakes, turtles and crocodiles, are threatened, the study found.
The research, published Wednesday in Nature, adds another dimension to a substantial body of scientific evidence that points to a human-caused biodiversity crisis similar to climate change in the vast effect it could have on life on Earth. “It’s another drumbeat on the path to ecological catastrophe,” said Bruce Young, co-leader of the study and a senior scientist at NatureServe, a nonprofit conservation research group. Such a collapse threatens humans because healthy ecosystems provide necessities like fertile soil, pollination and water supplies.
Among reptiles, particularly hard hit are turtles, with almost 60 percent of species at risk of extinction, and crocodiles, with half. In addition to habitat loss, both groups are depleted by hunting and fishing.
But the results also brought a sense of relief. Scientists have known far less about the needs of reptiles as compared with mammals, birds and amphibians, and they had feared the results would show reptiles slipping away because they required different conservation methods. Instead, the authors were surprised at how neatly the threats to reptiles overlapped with those to other animals.
“There’s no rocket science in protecting reptiles, we have all the tools we need,” Dr. Young said. “Reduce tropical deforestation, control illegal trade, improve productivity in agriculture so we don’t have to expand our agricultural areas. All that stuff will help reptiles, just as it will help many, many, many other species.”
The authors found that climate change played a role in the threat faced by 10 percent of species, suggesting that it was not currently a major factor in reptile loss. But the effects could be underrepresented, Dr. Young said, because scientists simply don’t know enough about many reptiles to determine whether a warming planet threatens them in the short term.
What’s clear is that the victims of climate change, reptilian and otherwise, will increase dramatically in coming years if world leaders keep failing to adequately rein in greenhouse gas emissions, which mostly come from burning fossil fuels. Last September the Komodo dragon, the largest lizard in the world, was classified as endangered in large part because of the rising temperatures and sea levels caused by climate change.
The reptile assessment includes 52 authors with contributions from more than 900 experts around the world. It took more than 15 years, in part because funding was hard to come by.
“Reptiles, to many people, are not charismatic,” Dr. Young said. “There’s just been a lot more focus on some of the more furry or feathery species.”
The team ultimately assessed 10,196 species. In 48 workshops between 2004 and 2019, groups of local specialists would gather and evaluate species one by one. The findings for each reptile were reviewed by a scientist familiar with the species but not involved with the assessment, and then again by staff from the International Union for Conservation of Nature’s Red List of Threatened Species, the most comprehensive global catalog of the status of animal and plant species.
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With 21 percent of species threatened with extinction, reptiles were found to be at higher risk than birds (of which about 13 percent of species are threatened with extinction) and slightly less than mammals (25 percent). Amphibian species, which have suffered from severe disease in addition to other effects, fare significantly worse, with about 40 percent of species in danger of extinction.
The study confirmed the results of a previous analysis that extrapolated extinction risk in reptiles based on a random representative sample.
Were all threatened reptiles to disappear, the authors found, they would take with them 15.6 billion years of evolutionary history. “Now we know the threats facing each reptile species, the global community can take the next step by joining conservation plans with a global policy agreement, investing in turning around the often too underappreciated and severe biodiversity crisis,” said Neil Cox, who co-led the study and also manages the Biodiversity Assessment Unit, a joint initiative of the I.U.C.N. and Conservation International to expand the Red List’s coverage.
This year, nations of the world are hammering out a new global agreement to tackle biodiversity loss. While the threats to species are clear — razing forests for beef cattle and palm oil, for example — it is much harder for countries to agree on how to stop them. A gathering in Geneva last month ended in frustration for many scientists and advocates, who described a lack of urgency from governments after two years of pandemic-related delays. Organizers added another meeting in June in hopes of making progress before the final one in Kunming, China, later this year.
The reptile research identified hot spots for imperiled reptiles in Southeast Asia, western Africa, northern Madagascar, the northern Andes and the Caribbean.
The assessment fills an important gap, said Alex Pyron, an evolutionary biologist at George Washington University who focuses on reptile and amphibian biodiversity and was not involved in the research. “This allows us to paint a much more detailed picture than was possible before,” Dr. Pyron said.
Scientists said they were particularly struck that habitat loss from deforestation, agriculture and other causes was a much larger threat to most reptiles than factors like pollution and climate change. Dr. Young, the co-leader of the study, said addressing issues like these would require significant changes in human behavior and economies given that “the ultimate cause is human consumption.”