Herbivorous animals are at a greater risk of extinction than predators and omnivores, according to a study published Wednesday in the journal Science Advances - whether they are mammals, birds or reptiles.
The risk is particularly high for herbivorous reptiles, such as turtles, and large herbivores, such as elephants. But the trend is true regardless of the habitat (desert, forests ...) and the class (mammals, birds, reptiles), according to this analysis covering more than 24,500 living and extinct species.
The study's authors, from several universities including Utah University and Imperial College London, write that predators are often seen as the most vulnerable, due to their large territories and the slow rate of growth of their populations, and because numerous studies have focused on specific and charismatic predators, effectively in danger.
In fact, "we have established that trophic level and size are important factors in the risk of extinction," the researchers say. The trophic level is the level of animals in the food chain: predators are at the top.
"There is so much published data that sometimes you just need someone to organize it," Trisha Atwood, the study's lead author, told Science.
The data compiled by the group looks at both the past (going back to the end of the Pleistocene 11,000 years ago), the recent (500 years) and the present, with similar conclusions. About a quarter of the herbivorous species studied here are now threatened with extinction, according to the reference classification of the International Union for the Protection of Nature (IUCN). 100% of herbivorous reptiles in marine environments are threatened.
Herbivores are also over-represented among extinct species.
Exceptions appear: piscivorous species and scavengers also had a relatively high level of risk. And the predators of the oceans are, in fact, very threatened.
Why would herbivores be more at risk, ultimately? The researchers cite one hypothesis: invasive species, whether rats, insects, or plants, disproportionately affect herbivorous reptiles, compared to omnivores and predators.
© 2020 AFP