ONE day, your grandchildren may open their science textbooks and read about elephants, tigers and lions as majestic, extinct creatures that once roamed the Earth like woolly mammoths and Triceratops.

    That is the message of a new paper, written by dozens of conservation biologists from around the world.

    The authors argue that many of the world’s biggest beasts could be extinct by 2100 if drastic measures are not taken. To forestall that future, governments and conservation organizations should implement several steps to prevent the mass extinction, the scientists report.

    “To underline how serious this is, the rapid loss of biodiversity and megafauna, in particular, is an issue that is right up there with, and perhaps even more pressing than, climate change,” Peter Lindsey, lion program policy initiative coordinator at conservation organization Panthera and a senior co-author of the paper, said in a statement.

    It’s not news that many of the world’s most beloved species are endangered. Poaching and the ever-creeping expansion of human settlement into wild terrain have decimated rhino and elephant populations, corralled big cats into ever-smaller territories, and forced the wildlife into conflict with human populations that live on the fringes of their habitat, several studies have shown. But the global impact of these trends can sometimes be hard to grasp.

    To get a sense of how bleak the picture is for the world’s nonhuman megafauna, the experts cataloged the species in peril across six continents — all of the species across the globe that the International Union for Conservation of Nature lists as threatened with extinction.

    When they looked at the prognosis for each of those species, the forecast was dire, the researchers found. Roughly 59 percent of the world’s big carnivore species (those heavier than 15 kilograms), such as Bengal tigers; and 60 percent of the world’s big herbivore species — such as white rhinos and Western lowland gorillas — could disappear from the Earth if critical steps are not taken.

    “There is a risk that many of the world’s most iconic species may not survive to the 22nd century,” the researchers wrote in the paper.

    The threat was particularly dire in sub-Saharan Africa and Southeast Asia, where much of the world’s biodiversity resides.

    (SD-Agencies)