Updated

If not for an elusive, antelope-like creature in the Arizona desert, the Department of Homeland Security might have a much easier time cracking down on illegal immigration in hotbeds along the border.

The Sonoran Pronghorn, which roams in Arizona, is an endangered species on the verge of extinction. As a result, environmentalists and governmental stewards have been repeatedly blocking Customs and Border Protection from expanding border technology in their habitat -- despite complaints that illegal immigrants are taking advantage of the security gap and doing plenty of harm to the environment in the process.

Concerns about a host of species for decades have prompted standoffs between border and environmental officials. Border officers have limited access to federal lands in some of the most heavily trafficked areas because of the harm the patrols could do to the environment. But pronghorn preservation is popping up more and more as a barrier to Border Patrol and catching the attention of some on Capitol Hill.

"The pronghorn can literally shut down production," said a Republican aide on the House Natural Resources Committee. "It could literally stop a project ... in its tracks."

A 2008 letter from the Fish and Wildlife Service obtained by FoxNews.com showed that the agency rejected a CBP plan to install seven towers throughout the Cabeza Prieta National Wildlife Refuge because of concerns it would lead to Sonoran Pronghorn extinction. The towers would have been part of the virtual border fence project that was partially suspended this year but is still underway in the area surrounding Cabeza.

The Department of Homeland Security is still fighting to install just one communications tower in the refuge, but continues to be met by objections from environmentalists. The Border Patrol has committed millions of dollars to various environmental projects meant to offset any potential damage, but critics argue that the species is too sensitive to bear the intrusion.

They describe the potential damage from the sensor towers as insidious.

George Nickas, director of Wilderness Watch, said the "human presence" necessary to build and maintain the towers would impact the environment. He said that if the tower helps crack down on illegal immigrant traffic, that traffic could be "diverted" to prime pronghorn habitat.

"They always end up causing a lot of unintended consequences," he said. "I don't know which straw will break the camel's back, so to speak, but I do think what's happening will incrementally lead to more and more difficulties."

Wilderness Watch is opposing the construction of the communications tower at Cabeza Prieta. Nickas would not say whether the group would file suit over the issue.

A spokesman for Fish and Wildlife said construction on the tower has begun and it was permitted by the refuge. He also said that Fish and Wildlife was open to discussing alternatives to the tower locations originally proposed by CBP. But the project was put on the hold before the issue could be worked out.

According to Fish and Wildlife, wild Sonoran Pronghorn numbers are down to about 80 in Arizona and they occupy less than 10 percent of their original range.

The other side of the argument is that illegal immigrants are doing massive harm to the environment and taxing government resources -- and that more Border Patrol and towers could actually do some environmental good.

"(Illegal immigrants) do more harm than Border Patrol would," said Rep. Rob Bishop, R-Utah. "Somehow we need to come up with what is indeed a priority and what is not a priority."

A 2007 memo from Fish and Wildlife detailed the extensive damage illegal immigration was causing to border wildlife refuges, including Cabeza Prieta. On the Buenos Aires refuge, the memo said 500 tons of trash is left behind by illegal immigrants every year, based on "conservative estimates." The memo said that in Cabeza Prieta, "large numbers" of drug smugglers were crossing the refuge and that vehicles and trash were being left behind. The memo said that resource officers, who are hired for "resource protection," were spending "100 percent" of their time dealing with border-related issues.

The GOP committee aide said drug and human smugglers make heavy use of Cabeza Prieta and that federal officials last year found seven relay units on the property -- used by cartels to communicate with one another. Cabeza Prieta is one of several border parks and refuges where signs have been posted warning visitors about the dangers of illegal immigrant-related activity.

"The thing that amazes me is that the environmentalists, including some of the governmental stewards, seem to lose track of the big picture," said T.J. Bonner, president of the National Border Patrol Council, the union for Border Patrol agents. "It doesn't do these species any good to allow literally thousands of people to go tramping through those areas on a continual basis."

He said Border Patrol is "sensitive" to the environmental concerns but that a balance needs to be struck.

"They're not going to just turn their agents loose and say 'go around and spin doughnuts in the desert'," Bonner said. "But at the same time, you have to do your job."

While he said his group is not a big fan of the virtual fence, the project could be effective with better technology and the boots-on-the-ground to respond to activity it picks up.

A spokeswoman for the Department of Interior, though, disputed characterizations that there is tension with Homeland Security.

"DHS and DOI work in close partnership with each other on all border issues and we will continue to do so. Fox News has covered the issue extensively but inaccurately, despite having ample evidence that shows there is no real conflict between border security and natural resource protection," spokeswoman Kendra Barkoff said in a written statement.