The decline of large predators such as big cats, wolves, sharks and giant whales may be “humankind’s most pervasive influence on the natural world,” causing prey animals to swell in population and throw food chains out of balance, a report says.
Humans have touched off the world’s latest mass extinction, according to the report, published Thursday in the journal Science, and the consequences are being felt on land and in water systems as large predators vanish. In addition to creating an overabundance of prey, the dwindling number of predators contributes to the spread of disease, wildfires and invasive species.
The decline of wolves in Yellowstone Park was cited as an example. Elk and deer in the park flourished and ate willow trees and saplings, threatening a crucial part of the forest on which other creatures rely.
The report also mentions the slaughter of lions and leopards by hunters and herders in parts of sub-Saharan Africa. As a result of the killings, disease-carrying olive baboons thrived without their top predators and inched closer to food crops and people. A reduction of big herbivores such as buffalo and wildebeest in East Africa through hunting is also a problem, the report says. Their demise led to increases in plants that fueled giant dry-season wildfires.
Americans don’t have to visit federal parks or sub-Saharan Africa to see the consequences, said Ellen Pikitch, a co-author of the report and a professor at Stony Brook University in New York. Many experience the problem every day in their own back yards. “People who live in North America know it’s hard to grow a garden because deer will eat it,” said Pikitch, a marine biologist. “The lack of wolf populations throughout North America has led to an expansion of the deer population.
“You may hate wolves. You might think they’re dangerous. But without them, the land changes,” Pikitch said. “Deer carry ticks. We humans become more susceptible to diseases such as Lyme disease.”
Wildlife advocates say efforts to protect one species of predator in the U.S. were set back when the Obama administration in April approved the removal 1,300 wolves from the endangered species list in the Rocky Mountains. It was the first time Congress had taken a species off the endangered list. The law allows limited hunting of the animals to begin this summer.
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