Roads pave the way for weed invasions

Improved roads in wilderness areas spread more invasive weeds than primitive roads, while roadless areas act as refuges for native species against invasions, according to two new studies. Cheatgrass, knapweeds and other non-native plants have invaded nearly 125 million acres of the American West. Roads promote invasion because vehicles can transport non-native seeds into uninfested areas, and disturbed roadsides give weed seeds a place to grow.