For Border Patrol agent Jose Proenca , picking up trash and watching where he walks is as much a part of his job as seeking out illegal immigrants.

Already charged with protecting the American border and slowing the tide of illegal immigrants in the hot and dangerous deserts of California and Arizona, agents are now finding themselves shouldered with more responsibility.

The Immigration & Naturalization Service has asked them to start picking up trash and avoid walking or driving on fragile natural habitats in their path.

"We normally instruct our agents to pick up the trash once they've apprehended a group (of illegal immigrants)", Proenca said. "As they're making their trip north they begin discarding stuff."

But that's only the beginning. In protecting 2,000 miles of the U.S.-Mexico border, agents can also no longer walk or drive on land with sensitive plants or disturb endangered species like the desert tortoise.

Most agents won't criticize INS policy openly, but privately, they worry environmental considerations are interfering with the job they were hired to do: controlling illegal immigration.

Not as diplomatic is Bob Goldsborough, president of American Immigration Control, a Virginia-based group that focuses on immigration issues.

"If there's a bank robber and the police are called in, you don't tell the police to stay off the flower beds," he said. "This is the same thing. It is simply a misdirection of their time and their energy."

Ultimately, Goldsborough said, green policies will make immigrant smugglers more successful at avoiding capture. Immigrants and others will know to cross on protected land, he said — places like the pristine wilderness around the San Pedro River in Arizona, a wildlife conservation area.

"It's a cockamamie idea," he said.

Back in the desert, Proenca will not criticize Border Patrol policy, but did say it made his job harder.

"We have to develop new alternatives in order to do the same job," he said. "What took maybe one agent to work a group before maybe takes two or three now."