Loss of predators in the food chain can alter the ecosystem

[webearthonline]

In the news:

Loss of predators in the food chain can alter the ecosystem
By Elizabeth Weise, USA TODAY

Take away the predators at the top of the food chain — the lions, tigers, wolves and cougars — and entire ecosystems start to change. A paper in today's edition of the journal Science suggests that humans' destruction of these top predators is causing reverberations worldwide in ways not apparent even a decade ago, including changes in the landscape and even increases in wildfires.

* A whale leaps out of the water in what is called breaching in a channel off the town of Lahaina on Maui, Hawai.

By Reed Saxon, AP

A whale leaps out of the water in what is called breaching in a channel off the town of Lahaina on Maui, Hawai.

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By Reed Saxon, AP

A whale leaps out of the water in what is called breaching in a channel off the town of Lahaina on Maui, Hawai.

Although the idea that there are serious ecosystem consequences to the removal of top predators isn't new, with this paper, "it's come of age," says Aaron Wirsing, a professor of wildlife ecology at the University of Washington in Seattle.

The review was conducted by two dozen scientists in six countries. It was funded by the National Science Foundation in the USA, Canada's Sciences and Engineering Research Council of Canada and others.

The loss of species at the top of the food chain has been happening worldwide either because humans believed they harmed livestock, competed for wild game or simply because ecosystems had become too fragmented to support them.

Overfishing led to declines of sea lions, the preferred food of killer whales, and they began eating sea otters, whose populations in Alaska's Aleutian Islands declined 90% from the late 1980s to 2005, according to the U.S. Geological Survey.

Worldwide, tigers have lost 93% of their historic range, says the International Union for Conservation of Nature. In the past three decades, numbers of African lions have fallen 48.5% to fewer than 40,000, says Andrew Wetzler of the Natural Resources Defense Council.

The absence of these predators creates an unpredictable cascade of effects, some of which it can take years to recognize, the researchers say.

"We now live in a world, really for the first time, where these big apex consumers are missing," says James Estes, a professor of evolutionary biology at the University of California-Santa Cruz and a lead author on the paper.

Examples cited in the research:

•Lions. The destruction of lions in Africa resulted in an explosion in the baboon population. These primates carry diseases that crossed over and began infecting nearby humans.

•Wolves. When wolves were reintroduced to Yellowstone National Park, they brought down elk and deer populations, allowing creekside willows to rebound, making a more fruitful environment for species living in and near the water.

•Whales. Whales in the southern oceans dive deep to eat , then return to the surface to breathe. Their feces deposit important nutrients from the ocean bottom into the upper water layers. When populations crashed because of industrial whaling, many ocean areas become much less able to support the simple animals and plankton on which the entire ecosystem was based.

•Wildebeest. A human-introduced disease, rinderpest, almost wiped out wildebeest in parts of Africa, which in turn led to a build-up of woody vegetation, resulting in devastating wildfires. When the disease was eradicated with a vaccine, the native grasslands returned and fires calmed.

"I think this might be the most important paper Science has published in a long time," says Paul Dayton, an oceanographer at Scripps Institution of Oceanography at the University of California-San Diego.

Humans need to not simply manage wildlife populations, but to realize they're managing often-complex ecological relationships, Dayton says.

[SouthernStar]

Question- How would the wild survive if we didn't exist and an important species died out anyway, would the ecosystem adapt or would it collapse?

[nikikay]

Well there would be a less likely chance of an important species dying out because, you have to face it, humans are the ones that cause most of the problems like over hunting, pollution. There could also be a chance that it would never happen because the food chain would be balanced out. And if it did, there are other preditors that eat the same thing, so it could be possible that the animals also adapt.

[Alexander]

I have a question.. How does the loss of predators increase wildfires?

[nikikay]

Um... I'm not sure... I really don't see how they are related.

[webearthonline]

I have a question.. How does the loss of predators increase wildfires?

According to this a build up of woody vegetation is created. I think that is fuel for fires, hence more fires.

[Alexander]

I have a question.. How does the loss of predators increase wildfires?

According to this a build up of woody vegetation is created. I think that is fuel for fires, hence more fires.

Oh! How interesting... Haha thanks.
Sad to see that any animal that's been wiped out are really effecting the Ecosystem.. what a shame.

[Quagga]

I'm afraid I'm not making the connection... If there is a loss in predators, then there should be an increase in herbivores, what with there being fewer threats and kills, and therefore, as there is more consumed due to an increased herbivore population, less vegetation. However, this isn't the case, so it's not making any sense to me?

[webearthonline]

I'm afraid I'm not making the connection... If there is a loss in predators, then there should be an increase in herbivores, what with there being fewer threats and kills, and therefore, as there is more consumed due to an increased herbivore population, less vegetation. However, this isn't the case, so it's not making any sense to me?

I think each line item had a link which was different in each eco system.
There would be an increase in herbivores with a loss of predators, but in this case it was offset by a human introduced disease which dropped the numbers of wildebeest even further than this totally a net loss. There are connections as things relate to each other. I think they were just trying to give some examples to make the point as opposed to go into a lot of detail about everything.

[Zelda0909]

Wolves will never be entirely wiped out! I just cant believe that... probly cuz I watched wolfs rain heh... anyway no wolves would be the worst thing in the world. no tigers no lions no wolves no fun no excitment no happyness. >: i still dont get how this affects fires i mean how do preditors affect wood in any way? oh well ill just guss i guss.

[nikikay]

I'm afraid I'm not making the connection... If there is a loss in predators, then there should be an increase in herbivores, what with there being fewer threats and kills, and therefore, as there is more consumed due to an increased herbivore population, less vegetation. However, this isn't the case, so it's not making any sense to me?

If that happened there would be a loss of Vegetation. So it would wipe out the herbivores as well, due to over population. Then quiet possibly the landscape would turn into a desert. It has happened before. Teddy Rosevelt wanted to preserve america's trophy bucks, so he killed all the predators in the area and the deer eventually died off.

[Vargen Saphia]

Question- How would the wild survive if we didn't exist and an important species died out anyway, would the ecosystem adapt or would it collapse?

It would adapt. Grass->grasseating animal -> predator. If all the predators/ meateaters died, they only things the grasseating animals could die of would be:
Disease
Accidents
Killed by other grasseaters
Age

and

NO FOOD OR WATER.



Therefore they would become quite a lot of them. Too many with too little grass too eat. It's like giving children cookies, if you make sure there's enough, they'll be happy, but if there comes too many of them, you will run out of cookies before every1 had gotten one.
So they would eat, eat and eat, till there's no food left, then die of starvation.
And then grass would grow a low, and the few survivors of grasseaters can get fat.

[Quagga]

I think each line item had a link which was different in each eco system.
There would be an increase in herbivores with a loss of predators, but in this case it was offset by a human introduced disease which dropped the numbers of wildebeest even further than this totally a net loss. There are connections as things relate to each other. I think they were just trying to give some examples to make the point as opposed to go into a lot of detail about everything.

Sure, disease can bring any population down, but again, how does the loss of predators cause this? It was the disease that caused it, not the predators? It was a human-introduced disease. This was not caused by the loss of predators, but by humans. Maybe the loss of predators increased the spread, but they wouldn't have been able to guarantee eradication of the disease via predators anyways.

Loss of predators > increase of prey > more eaten > less food > decrease in prey population > potential extinction

Loss of predators + introduction of herbivore disease > greater spread of disease > herbivores dying > increase of wood

No loss of predators + introduction of herbivore disease > steady spread of disease > herbivores dying > increase of wood

Researching Rinderpest, it sounds like it was a very contagious disease. Even if predators were around, the wildebeest population would have fallen;

Death rates during outbreaks were usually extremely high, approaching 100% in immunologically naïve populations.[11] The disease is mainly spread by direct contact and by drinking contaminated water, although it could also be transmitted by air.

Initial symptoms include fever, loss of appetite, and nasal and eye discharges. Subsequently, irregular erosions appear in the mouth, the lining of the nose, and the genital tract.[11] Acute diarrhoea, preceded by constipation, is also a common feature.[12] Most animals die 6–12 days after the onset of these clinical signs.

It wasn't the loss of predators, then, that caused it. Instead, it simply contributed to the increase of wood. In no way do I think this should be included, then, in this report; it makes it sound like it was the cause of the increase of wood. It only helped, and even so, I am very doubtful that a balanced predator population could have even stopped it.

[webearthonline]

They say that herds are stronger and healthier with the predators.
There are cases where the herd populations get in trouble without predators.
It might be the case where a sick or diseased animal might have been taken by predators, but without the predators this sick animal then infected more of the herd.

[nikikay]

Most predators do go for the sick and weak prey. This does make some sense... But I still don't see how it has to do with fire.