Global decline of large plant eaters may lead to 'wildlife deserts'
Some of the richest ecosystems on Earth, including Africa's savannahs and forests, could become wildlife deserts because of the decline of large herbivores, researchers claim.
Many populations of "big fauna" animals such as rhinoceroses, zebras, camels, elephants and tapirs are already diminishing or threatened with extinction.
If the trend continues the habitats where such creatures make their home will be transformed into "empty landscapes", as the knock-on effects impact both on predators and plant life, a study suggests.
Lead scientist Professor William Ripple, from Oregon State University, US, said: "I expected that habitat change would be the main factor causing the endangerment of large herbivores. But surprisingly, the results show that the two main factors in herbivore declines are hunting by humans and habitat change. They are twin threats."
"Our analysis shows that it goes well beyond forest landscapes, to savannahs and grasslands and deserts. So we coin a new term, empty landscape."
The research, published in the journal Science Advances, focused on 74 large herbivore species and found that 25 now occupied only 19 pc of their historical ranges on average.
The scientists wrote: "Without radical intervention, large herbivores (and many smaller ones) will continue to disappear from numerous regions with enormous ecological, social and economic costs."
They pointed out that competition from livestock production, which has tripled globally since 1980, had reduced herbivore access to land, forage and water and raised the risk of disease transmission.
Hunting for meat consumption and the global trade in animal parts had also taken a heavy toll.
Africa's western black rhinoceros was declared extinct in 2011 as the value of rhino horn soared.
"Horn sells for more by weight than gold, diamonds or cocaine," said Prof Ripple.
Herbivore loss was likely to rob carnivores such as lions and tigers of food, diminish seed dispersal, slow the cycle of nutrients from vegetation to the soil, and alter the habitats of smaller animals including fish, birds and amphibians.
With fewer large herbivores clearing vegetation and creating natural fire breaks, wildfires were likely to become more frequent and intense.
As a group, terrestrial herbivores include around 4,000 known species and occupy many types of ecosystem on every continent except Antarctica.
The majority of threatened large herbivores lived in developing countries, particularly Africa, India and South-East Asia, said the researchers.
Prof Ripple said: "We hope this report increases appreciation for the importance of large herbivores in these ecosystems. And we hope that policy makers take action to conserve these species."