Species extinction causes "empty landscapes"

The extinction of large herbivores has drastic consequences for ecosystems

The black rhino or black rhino is one of the most endangered herbivorous mammal species. © Oregon State University
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Extinction with far-reaching consequences: Zebras, elephants, rhinos and many other large herbivores are nearing the end of the world. 60 percent of them are threatened with extinction. For the affected ecosystems that has drastic consequences: If the large herbivores disappear, they could turn into "empty landscapes, " warn US researchers in the magazine "Science Advances".

Thousands of animal species are threatened with extinction worldwide. Some of them can only be saved with immediate and intensive protection measures, for others, probably any help comes too late. This is especially evident for us when large and familiar animals suddenly disappear: rhinos, zebras and elephants are among the endangered species, but camels and tapirs may soon be found only in animal husbandry and in the zoo.

Double threat: hunting and dwindling habitat

Researchers around William Ripple of Oregon State University have now analyzed what the decline and extinction of such large herbivores would mean for the world's ecosystems. They focused on 74 species of the world's largest herbivores: animals with an average weight of over 100 kilograms. Special attention was paid to the threatened status of the species and the causes of the threat, as well as to the importance of animals to their ecosystem.

"I expected that changing habitat is the main reason for the threat of large herbivores, " says Ripple. "Surprisingly, our results show that the two most important factors are human hunting and habitat changes. There is a double threat. "

Rhino sells better than gold and diamonds

One reason is that wild animals compete with livestock. Since 1980, the world production of meat has tripled. Along with growing agriculture, this is making it increasingly difficult for wildlife to find food and access to water sources. In the small and constricted populations, diseases also spread faster. display

Zebras are also on the list of endangered herbivores. Halska Hrabar

The other crucial factor, the hunt by humans, happens for two reasons, according to the authors. On the one hand, around one billion people worldwide live on hunted meat. However, the trade in animal body parts for "medical purposes" is just as important: "The market for medical applications can be very large for some parts, such as rhinoceros horn, " says Ripple. "Horn sells better by weight than gold, diamonds or cocaine." In order to protect the animals effectively, this demand must sink drastically the West African black rhinoceros has been extinct since 2011.

"Empty Landscapes" in Asia and Africa

Mainly in the developing countries the big herbivores are threatened, especially in Southeast Asia, India and Africa. The only European threatened species is the bison, the European bison. None of the endangered species studied live in North America - according to the authors, this is because this continent has already lost most of the major mammal species through prehistoric hunting and altered habitats.

More than 20 years ago, a similar study on species extinction in tropical rainforests had evoked the image of "empty forests": the trees and the surrounding vegetation Although initially outlasting the extinct species, these sensitive ecosystems suffer from long-term consequences.

Ripple and his colleagues carry on this idea further, and in their study paint the concept of "empty landscapes". Because with the loss of large herbivores, the affected ecosystems will change drastically, the researchers write: Predators such as lions and tigers will be missing the prey, so that their existence will decrease. An earlier study on the existence of endangered predators had also already revealed this connection.

Hope for greater attention

Previously eaten by animals and excreted plant seeds are also disseminated worse. In addition, the circulation of nutrients between plants and soil changes. The plague of the North American megafauna about 12, 000 years ago already shows how this situation can be reduced. As the vegetation changes, so does the danger of forest and bush fires. Finally, the habitat for smaller species such as birds, fish and amphibians is changing.

"We hope that this report will raise awareness of the importance of large herbivores for these ecosystems, " says Ripple. International cooperation is needed to help developing countries protect biodiversity. Because especially local people are in demand. "And we hope politicians take action to protect these species." (Science Advances, 2015; doi: 10.1126 / sciadv.1400103)

(Oregon State University, May 4, 2015 - AKR)