Mexico drug cartels growing marijuana on US National Parks and Forests are severely polluting the area due to the highly toxic chemicals used in cultivation.

From the AP (via Yahoo News):

National forests and parks — long popular with Mexican marijuana-growing cartels — have become home to some of the most polluted pockets of wilderness in America because of the toxic chemicals needed to eke lucrative harvests from rocky mountainsides, federal officials said.

The grow sites have taken hold from the West Coast’s Cascade Mountains, as well as on federal lands in Kentucky, Tennessee and West Virginia.

Seven hundred grow sites were discovered on U.S. Forest Service land in California alone in 2007 and 2008 — and authorities say the 1,800-square-mile Sequoia National Forest is the hardest hit.

Weed and bug sprays, some long banned in the U.S., have been smuggled to the marijuana farms. Plant growth hormones have been dumped into streams, and the water has then been diverted for miles in PVC pipes.

Rat poison has been sprinkled over the landscape to keep animals away from tender plants. And many sites are strewn with the carcasses of deer and bears poached by workers during the five-month growing season that is now ending.