What Happens When Predators Disappear
The loss of wolves in the American West set off a cascade of changes to the region's food web. Courtesy of Flickr user WSK_2005.
Eliminating predators from an area may be seen as a good thing; you’ve gotten rid of the animal that has been killing off your livestock or even your neighbors. Others often see the loss of these species with a somewhat sad, romantic eye; how awful to never again see such a creature. But the reality of the loss of predators is far worse, say ecologists reporting in Science, and “may be humankind’s most pervasive influence on nature,” they write.
Part of that is because the worst extent of such a disappearance—extinction—is irreversible, unlike other environmental impacts, such as climate change. But it’s more because the loss, or even reduction in numbers, of predators in an ecosystem can set off something caused a “trophic cascade” in which the change in predator population has effects across the food web and ecosystem. For example, when wolves were eliminated from the American West, there were changes in the elk population and the vegetation the elk ate.
“Trophic cascades have now been documented in all of the world’s major biomes—from the poles to the tropics and in terrestrial, freshwater and marine systems,” the scientists write.
But changes to the food web aren’t the primary problem for human populations; the effects on ecosystem processes are often more dangerous. And many of these processes are big enough that even people in industrialized nations cannot protect themselves. The changes in vegetation that occur when the herbivore population is allowed to rise unchecked can change the frequency and intensity of wildfires. Infectious diseases can become more common; for example, in some parts of Africa where lions and leopards have become scare, populations of olive baboons have changed their behavior patterns, increasing their contacts with the humans nearby. Intestinal parasites have become more common in both the baboons and the people.
Then there are changes to soil bacteria, water availability, biodiversity and a host of other ecosystem features that we depend on to grow our food, keep our environment habitable and stay healthy. The scientists conclude:
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.
We can’t predict what will happen when a predator is lost from an ecosystem; there are too many unknown ways that species interact and the processes take place over scales of tens to thousands of square kilometers. The true effect of a loss can’t be known until years or decades after it has taken place. It’s another reason to save these incredible creatures—for our futures.
With this reminder of the importance of predators, we’ve decided to hold Predator Week here at the blog. What’s your favorite predator, either existing or extinct? Which ones would you be sad to lose forever?
Categories: Natural Disasters, Wildlife
The cheetah is nearing extinction due to poaching and urban sprawl. There’s not enough genetic disparity to ward off the perils of inbreeding. Although the biological impact of an extinct cheetah population may be minimal (due to the number of competing predators) it would be truly devastating to not have a cat that can sprint up to 60mph.
by Bruce Leesa on Jul 18, 2011 at 12:07 pm
It’s hard to decide between the wolf and the lion…The lions because they have almost a swagger…and pride about them..truly king of the beasts….The wolf for a different reason, they are wilder in their behavior…more instinctive in a way…but there is a look of knowledge in their eyes…like they have secrets to share if we would listen.
by lorraine on Jul 18, 2011 at 1:24 pm
Too many for a “favorite,” but it would be cool to know more about the actual Canus dirus.
by Brittany on Jul 18, 2011 at 1:31 pm
Birds of prey such as hawks and eagles rank near the top of my list.
by Kathy on Jul 18, 2011 at 8:55 pm
[...] Yesterday I asked you, the readers, about your favorite predators. Mine, well, that has to be the snow leopard (Panthera uncia). I remember seeing them at the zoo when I was a kid and being fascinated by them, so out of place in America and yet so familiar, like a bigger version of my own kitty. [...]
by The Vanishing Cats | Surprising Science on Jul 19, 2011 at 10:21 am
I´d say that my favorite one are wolves. I guess that is due to the flick I saw years ago: “White Fang” with this actor i cant remember ; Nevertheless I´m awared that the history was kinda based on unreal events…
by Manuel on Jul 19, 2011 at 11:43 pm
Mine has to be the Bengal Tiger,the most majestic beautiful predator on earth.
by veena Raina on Jul 20, 2011 at 5:39 am
Rehabilitating endangered species where each individual can still make a difference to saving the species.
by John Gubbons on Jul 20, 2011 at 8:55 am
[...] started out Predator Week on Monday with a study that looked at what happens when predators disappear from an ecosystem. But why do we [...]
by What Preys on Humans? | Surprising Science on Jul 22, 2011 at 10:59 am
[...] 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. [...]
by Zoe – It's Our Nature : Life Without Big Animals on Jul 25, 2011 at 8:59 am
Hands down it’s got to be the grizzly. Nothing else comes close. It’s smart. Adaptive. Omnivorous. And it has no qualms about eating the odd hiker in a pinch.
On a side note, I’ve seen nearly every film featuring Bart the Grizzly and I have to say we lost one of the greats when he passed away.
by Mark Heber on Aug 4, 2011 at 10:44 pm
I like the Siberian tiger and Snow Leopard, they might become extinct too.
by Joanna on Aug 8, 2011 at 9:23 pm
Some would say that the killing off of your neighbors by wolves is a good thing…
by Ric on Sep 14, 2012 at 4:17 pm
“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.”
Translation: everything environmentally bad that happens is our fault. Give these people enough time and they’ll come up with reasons we’re responsible for the dinosaur extinctions.
by John on Sep 16, 2012 at 5:34 pm