Throughout the Great Plains and Rocky Mountains, exotic plants are jeopardizing the integrity of natural ecosystems (U.S. Geological Survey’s Invasive Species Working Group 2000). The National Park Service has identified management and control of invasive, exotic plants, especially state-listed noxious weeds, as a high-priority resource management issue. Noxious weeds are invasive plants that threaten agricultural crops and rangeland and whose control is mandated by state law. In the Intermountain Region, resource managers in 19 National Park System units have prioritized areas where exotic plants need to be inventoried and their population distribution mapped before effective and efficient management can be implemented (Intermountain Regional Office 2001).

At the request of the Intermountain Region, the Great Plains Cooperative Ecosystem Studies Unit organized a team of range ecologists and a remote sensing specialist at the University of Nebraska–Lincoln to inventory and map noxious weeds within two park units in New Mexico: Capulin Volcano National Monument and Fort Union National Monument. During the initial stages of this effort, we proposed to map all noxious weeds that are included on the New Mexico noxious weed list over the entire area of both national monuments. Review of the plants at these national monuments, however, led us to modify our original objective. Only one noxious weed—field bindweed (Convolvulus arvensis)—was known from Capulin Volcano. Field bindweed was also the only known noxious weed from Fort Union. Additional exotic plants not classified as noxious weeds were present at both national monuments, however. Without management, many of these exotics have the potential to become state-listed. Instead of mapping all the exotic plants in each unit, we used a ranking system to first determine which exotic plants were serious pests and then mapped only those species.