BOSTON (

MainStreet

) -- What could be done with $100 million dollars? As it turns out, a lot of bloodshed.

That is how much is spent every year by Wildlife Services,

a branch of the U.S. Department of Agriculture's Animal and Plant Health Inspection Service

, to kill hundreds of thousands of animals.

The species most commonly targeted by Wildlife Services' lethal control program are predators such as wolves, bears, coyote and mountain lions. An estimated 100,000 native carnivores are killed each year, with approximately 2 million animals killed since 2000.

The purpose is often to prevent losses of either livestock or game species such as deer and elk that are popular targets for hunters. Some of the methods used for controlling predators include trapping, aerial gunning, denning (killing young in their dens) and using poisons such as Compound 1080 or sodium cyanide M-44.

"Driven by narrow agricultural interests, these predator control activities often ignore the greater public need for a healthy environment, fiscal responsibility and safe public lands, raising some serious questions about how the program is being administered," says

a press release

from the Natural Resources Defense Council, which holds the position that Wildlife Services is wrongfully scapegoating predators.

USDA Wildlife Services is distinct as the only federal program that markets its services -- killing native predators native predators and other "nuisance" wildlife -- to ranchers, state wildlife management agencies and even corporations, despite a mission "to resolve wildlife conflicts to allow people and wildlife to coexist." It not only seems contradictory as a mission; it has also caused several conservation groups to accuse Wildlife Services of having a profit-driven conflict of interest.

Also see: How to Stop Spending $2B a Year Killing the Pets We Love>>

The program is so notorious that last year it became the subject of

a three-part expose

in

The Sacramento Bee

by Pulitzer Prize-winning journalist Tom Knudson. He found that the programs went on with minimal monitoring and also killed tens of thousands of non-target animals, including cats, dogs and river otters.

"There will obviously be times when livestock and predators come into conflict, when coyotes kill lambs and black bears become too accustomed to humans and cause genuine harm," began a scathing editorial on the Wildlife Services program that

appeared in The New York Times

this past summer, "But Wildlife Services' lethal damage is broad and secretive."

The environmental nonprofit Predator Defense argues that lethal control is not only harmful to sensitive predator populations, but to ecosystems that rely on healthy predator populations to function.

As it turns out, science is on their side.

In the 1960s a

"green world" hypothesis

suggested that predators help plants and trees thrive by keeping herbivores such as deer in check. In the Rocky Mountain West, exactly that happened in what's called "trophic cascade": The absence of wolves in the region led to lots of deer that feasted without check on trees and other plants, killing them off.

In 1995, William Ripple, director of Oregon State University's Trophic Cascades Program, had the chance to study the phenomenon in action. Ripple saw firsthand how trees along stream banks in Yellowstone National Park rebounded with the reintroduction of the gray wolf to control the elk populations -- in fact, not only were trees and vegetation restored, but beavers, songbirds and trout that had been absent for decades suddenly returned.

Not only has the reintroduction of the gray wolf to Yellowstone Park improved the regional environment, it's also benefited the economy enormously.

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According to a 2006 University of Montana study, wolves draw in an estimated $35 million a year in tourist revenue to the greater Yellowstone area. That dwarves the estimated losses of $500,000 per year incurred by hunters/outfitter businesses because they smaller populations of game to hunt.

Surveys of visitors to Yellowstone Park found that the main reason people go there is to see grizzly bears and wolves. Another study by Defenders of Wildlife says the reintroduction of the Mexican wolf to the Southwestern U.S. has generated average annual net benefits between $3.2 million and $3.8 million for Arizona and New Mexico.

Naysayers claim that livestock losses caused by wolves detract from the economic stimulus they provide, but

statistics paint a different picture

.

A USDA report from 2011 found that only 0.23% of American cattle were lost to native predators or domestic dogs, with most livestock fatalities due to bad weather or disease, not predators. Livestock losses from wolves or other carnivores peaked one year at only $60,000.

So what should be done with the predator control program?

A summer article

in the peer-reviewed journal Conservation Letters

decried lethal predator control as "ineffective" at controlling predation rates. The authors recommended instead that Wildlife Services use wildlife conflict management techniques and train livestock producers in nonlethal control. They argued for a ban of lethal control in federal wilderness areas and for the purpose of artificially boosting game populations.

If Wildlife Services ignore these recommendations, the authors of the article argue that it will continue to have negative consequences, including "the loss of many ecosystem services that benefit human society directly and indirectly."