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Life Without Big Animals

From wolves to sharks, apex consumers keep ecosystem in balance

Tiger in Belize. Photo by Prospero973

What happens when we shoot the wolves, hunt down the elephants, harpoon the whales, fish out the salmon?

The answer is: it’s really bad for us, not just for those animals. And if we needed proof, we now have it.

A new study, published in Science magazine, shows how entire ecosystems become unbalanced, even destroyed, when you take out the “apex consumers” – the top predators like the wolves, sharks and tigers, and the big herbivores like the elephants and whales.
Among the many examples:

A field in Yellowstone after the wolves were eradicated and (right) four years after they were reintroduced. Photo by Science magazine.

When the wolves were eliminated from Yellowstone National Park, the elk overpopulated, roamed in areas where they did a lot of damage, and changed the whole landscape. Since the wolves were reintroduced, the willows, for example, have grown back, the creeks are no longer eroding and are now shaded, so the trout are more numerous and healthy. (Who would have made the connection that the trout depend on the wolves?)

As more and more whales were hunted down, one of the many consequences was that the oceans were starved of whale poop which provided essential nutrients to the ocean.

And as big cats have disappeared from the tropics, the smaller herbivores have eaten their way through the seedlings to the point where new trees are no longer growing.

More than anything else, the top predators and big herbivores are the chief protectors of all these ecosystems.

The new study says that “The loss of apex consumers is arguably humankind’s most perverse influence on the natural world.”

And the scientists add:

“We propose that many of the ecological surprises that have confronted society over the past centuries – pandemics, population collapses of species we value and eruptions of those we do not, major shifts in ecosystem states, and losses of diverse ecosystem services – were caused or facilitated by altered top-down forcing regimes associated with the loss of native apex consumers or the introduction of exotics.

“Our repeated failure to predict and moderate these events result not only from the complexity of nature but from fundamental misunderstandings of their root causes.”

Many of these large animals became extinct or functionally extinct in centuries gone by, most likely because they were hunted down by humans – like the wooly mammoth, the bison and the saber-toothed tiger.

For a before-and-after view of what’s happened to various key ecosystems due to the removal of the apex consumers, see this article in Wired magazine and this post at Smithsonian.

What do you say? Which large animal is your favorite apex predator or top herbivore? Let us know in a comment or on Facebook.