The U.S. Forest Service released a report Wednesday, saying three-quarters of rangelands are in relatively good ecological shape and that there's enough forage for wildlife and livestock.
But the report says there are thousands of non-native plant species in the U.S. and the 16 most pervasive ones have affected 126 million acres. In some regions, invasive plants are spreading at a rate of more than six square miles a day.
Most rangelands are in the West.
Federal officials say the size and scope of the problem make determining the amount of effort needed to combat invasive species difficult. The report notes that in 2000, the damage and control efforts resulting from the annual costs of invasive plants was about $137 billion.