Collectively, invasive plants are estimated to spread as fast as 200 acres per hour on federal lands in the western U. S. Invasive weeds have invaded approximately 17 million acres of public lands and have quadrupled their range from 1985 to 1995. This value does not include the rate of spread on non-federal lands, so the rate of spread and its impact is actually much greater. The negative economic and ecologic impacts of invasive plants are many and include:

• Agricultural losses for both ranchers and farmers
• Damaged habitat of threatened and endangered species (flora and fauna)
• Displaced native vegetation and lowering of biodiversity
• Human health problems (allergies, irritants, infections, etc.)
• Increased requirements for land management and lower property values
• Increased soil erosion, damaged watersheds, water quantity and quality problems, and damaged fisheries
• Reduced opportunities for land use and recreational activities (hunting, birding, hiking, camping)