Approximately 60% of giant plant eating animals, including rhinos, elephants and gorillas, are at risk of extinction, according to new research.
Analysis of 74 herbivore species, published in the journal Science Advances, saw poaching and habitat loss creating perfect conditions for extinction. A previous study of large carnivores, such as tigers, lions and leopards, showed similar declines.
Oregon State University professor William Ripple led the research looking at herbivores weighing over 100kg, from the reindeer up to the African elephant.
"This is the first time anyone has analysed all of these species as a whole," he said.
"The process of declining animals is causing an empty landscape in the forest, savannah, grasslands and desert."
Oxford University's professor David Macdonald, of the school's Wildlife Conservation Research Unit, was on the team of 15 international scientists.
"The big carnivores, like the charismatic big cats or wolves, face horrendous problems from direct persecution, over-hunting and habitat loss, but our new study adds another nail to their coffin - the empty larder," he said.
"It's no use having habitat if there's nothing left to eat in it."
The research shows that the decline in populations is being driven by a number of factors including habitat loss, hunting for meat or body parts, and competition for food and resources with human raised livestock.
With rhino horns worth more than gold, diamonds or cocaine on the illegal markets of China, rhinos could be extinct in the wild within 20 years in Africa, according to the research.
The consequences of large wild herbivore decline include:
- Loss of habitat: for example, elephants maintain forest clearings by trampling vegetation
- Effects on the food chain: large predators such as lions, leopards, and hyena rely on large herbivores for food
- Seed dispersal: large herbivores eat seeds which are carried over long distances
- Impact on humans: an estimated one billion people rely on wild meat for subsistence while the loss of iconic herbivores will have a negative impact on tourism
The biggest losses are occurring in South East Asia, India and Africa.
Europe and North America have already lost most of their large herbivores in a previous mass extinction.