by Christian Edwards
SYDNEY, Jan. 11 (Xinhua) -- In a review published Saturday in the journal Science, an international team of scientists and co- author Dr. Mike Letnic from the University of NSW are sounding an alarm that the extinction of the world's top carnivores will decimate the world's ecosystems.
Dr. Letnic, speaking from UNSW's center for ecosystem science, said that the loss of animals at the top of any food chain can have cascading effects on the surrounding environment.
The theory follows that this can also effect climate change.
Australia is currently witness to these potential changes with predatory sharks the subject of intense parliamentary debate in Western Australia after a spate of attacks led state government to set bait drum traps.
Even more urgent action is needed to protect the Australian dingo -- the bareen island nation's largest onland predator, from the "unforseen" environmental consequences that will accompany further declines in their numbers, the international team of ecologists has warned.
Over the last two centuries, large mammalian carnivores have experienced dramatic declines in population and geographic range globally, leading to a variety of negative ripple-down effects for ecosystems -- the extent of which are not yet fully understood.The international review published in Science examines the conservation status and ecological impact of the world's 31 largest mammalian carnivores, including iconic big cats like the African lion and cheetah, American and European bears and wolves, and dingoes.
Professor William Ripple of Oregon State University said the environmental importance of these animals is underestimated, adding the current wildlife management practices to limit or eradicate top predators in some regions is "outdated," and that new strategies are needed to facilitate co-existence between humans and top predators.
"There is now a substantial body of research demonstrating that, alongside climate change, eliminating large carnivores is one of the most significant anthropogenic impacts on nature," the review says.
A loss of top predators would have "wide-ranging influences on virtually all other species" in an ecosystem and could cause increased desertification, greater susceptibility to invasive species and wild fires, altered disease dynamics, and a diminished ability to naturally capture and store carbon emissions. The authors also said there will be many unforeseen consequences because scientists have "only just begun to understand the influences of these animals in the fabric of nature."
Letnic's work has focused on ecosystem conservation and management strategies, and has revealed some important findings about what happens to Australian plants and small mammals when dingo numbers decline.
"The balance of ecosystems can shift dramatically," he said. " Research on dingoes from Australia shows that populations of foxes and kangaroos irrupt following the removal of dingoes. Foxes in particular pose a considerable threat to small native mammals."
"Overall, the suppression of dingoes has probably contributed to the endangerment and extinction of small marsupials and rodents over much of the continent," said Letnic.
More than 60 percent of the animals included in the review are considered by the International Union for the Conservation of Nature to be threatened and at risk of local or complete extinction, and 77 percent are experiencing continuing population declines.
Letnic believes that the model could be applied to almost all known ecosystems, noting that ocean ecology -- so important to Australia -- would be compromised. A situation where, for example, the removal of sharks could be catastrophic in Australian waters.
"It translates across many ecosystems so we find these effects occurring with sharks," he said.
"We know that removing sharks from ecosystems also produces these dramatic and often unforeseen effects, and similarly crocodiles in northern rivers does produce changes in the river ecosystems."
The paper is particularly timely in Australia's west, where the state government is moving to catch and destroy all deadly sharks - - from Great Whites, Bull and Tiger sharks that are of a size and disposition to threaten humans.