A new study published in Science Advances is being described as "horribly bleak," at least as far as rhinos, camels, and elephants are concerned: It finds that the majority of the planet's giant herbivores face the risk of extinction. The wildlife ecologists write that while about 4,000 species qualify as a "terrestrial mammalian herbivore," they zeroed in on just 74 such species whose mean adult body mass is 220 pounds. It's the "first time" just those large species have been viewed collectively, says study leader William Ripple of Oregon State University; per the International Union for the Conservation of Nature, 44 of them, or about 60%, are threatened with extinction. The researchers identified "twin threats": habitat change—25 of the 74 have lost 81% of their historical range—and hunting, with an estimated 1 billion people consuming wild meat.
Their loss could have a dire ripple effect, the scientists explain: "Large herbivores are irreplaceable as seed dispersers," they write, "able to ... deliver many more seeds per defecation event over longer distances" as compared to other animals. It's one of many things they impact, from the frequency of wildfires to the creation of new channel systems in swamps. Ripple previously looked at large carnivores through the same lens and found similar issues, and he tells the BBC his latest study "adds another nail to [the carnivores'] coffin. It's no use having habitat if there's nothing left to eat in it." A press release notes that of the species reviewed, just one—the European bison—is found on the continent of the same name, and none in North America, thanks in part to "prehistoric hunting." Southeast Asia, India, and Africa are home to the bulk of the threatened giant herbivores. (Meanwhile, US zoos are letting their elephants die out.)