http://www.csmonitor.com/2003/0610/p01s03-usgn.html
International drug cartels dominated by Mexicans pose the greatest threat to U.S. national parks since their creation more than a century ago, the Christian Science Monitor says. It is illegal marijuana farming. Bill Tweed, chief naturalist at Sequoia National Park in California, says that growers are “killing wildlife, diverting streams, introducing nonnative plants, creating fire and pollution hazards, and bringing the specter of violence.”
Marijuana seizures in California national forests jumped from 45,054 plants in 1994 to 495,000 last year. One seizure at Sequoia netted 34,000 plants in five locations at an estimated street value of $140 million. Since Sept. 11, 2001, drug farming has spread from remote forests to more-public national parks. Tighter security on U.S. borders has raised the incentive for domestic cultivation.
“The most [visitors] used to worry about is running into a grizzly bear. Now there is the specter of violence by a masked alien toting an AK-47,” says David Barna, chief spokesman for the National Park Service.