Print PageInvasive species management in the United States took a giant step forward with the Invasive Species Executive Order of 1999. Enacting this order put into motion mechanisms for coordinating actions among agencies for preventing and controlling invasive species. The National Invasive Species Council has published two dynamic national plans with prevention of introductions as the first line of defense, and with early detection and rapid response being the second line of defense for invasions. Provided these defenses are effective, then invasions should not occur or when they do occur, they should be met with detection and responses to eradicate them before they spread. Once invasive species become established then the plan calls for control and management of further spread and for the restoration of high valued ecosystems. This presentation will review our status in using these defenses in combating introductions and spread of invasive species in grasslands, shrublands and savannas. I will also consider the idea that adaptation or coexistence may be the ultimate fate with certain problematic species, but the management for coexistence is an understudied, yet much needed avenue for research to aid management.
Results/Conclusions
The best plant example of an eradication program has been witchweed (Striga asiatica) in croplands. Infestations of this grass parasite have shrunk by 99%, but it has taken over 50 years and strong cooperation to reach this stage. Eradication of invasives within natural ecosystems will take similar efforts. Leafy spurge (Euphorbia esula) and salt cedar (Tamarix spp.) are examples of control successes driven by insect biocontrol agents. Not all invasive species have identified unique biocontrol agents. Cheatgrass (Bromus tectorum) has potential microbial agents, but most are not unique to the invasive species. For species like cheatgrass, protecting areas that lack the invasive is critical. Protection requires understanding the colonization and naturalization process. Preliminary work indicates that spatial relationships among native perennial plants may play a vital role in understanding if a community is approaching a threshold where ecosystem resilience is compromised and conversion to a cheatgrass monoculture is merely one fire away. Traditional monitoring of species composition may not be adequate to detect this threat. Additional tools, such as measurements of intercanopy gaps, may provide early warnings of impending cheatgrass invasion risks. Investigations into the genetic variation of native plant materials may provide tools for restoration success thus allowing native plant coexistence with invasive plants.
