More than 50,000 non-native plants, insects, and animals have been introduced to the U.S. Scientists estimate that 4,500 of them are arthropods. “Insect invasions are enabled by humans’ ever-expanding trade and travel networks,” says U.S. Forest Service scientist James Vogt. “Across the globe, invasive species are crossing borders at alarming rates.”
In some states such as Florida, an average of 15 newly introduced species become established each year. Not all non-native species are destructive. “Some invasive insects either have or certainly will alter the landscapes where their hosts occur,” says Vogt.
Some of the most destructive introduced insects include the hemlock woolly adelgid, which attacks eastern hemlock and Carolina hemlock; the balsam woolly adelgid, which has destroyed most of the mature fir trees in the Great Smoky Mountains National Park; the redbay ambrosia beetle, which threatens redbay and sassafras trees across the Southeast; and the emerald ash borer, which has killed tens of millions of ash trees in the U.S.
Vogt is deputy program manager of the Forest Service Southern Research Station’s Forest Inventory and Analysis (FIA), which nationwide represents the longest-running and most comprehensive survey of forested land in the U.S. Through FIA, the Forest Service collects information on the status, trends, and resource conditions for all forest lands in the country. Historically, FIA focused on timber resources, and although this is still a priority, FIA now collects information on many forest attributes, including invasive plant species, lichens, soil properties, and carbon storage. Vogt and his colleague Frank Koch, a research ecologist at the SRS Eastern Forest Environmental Threat Assessment Center, recently published an article in American Entomologist outlining the role of FIA data in invasive insect research.
FIA data are extremely useful in many aspects of preventing, detecting, and managing invasive insects, as well as forest restoration after invasions. Most of these applications are informed by FIA data on plant distribution and abundance. Because forest pests typically require a certain plant host, the presence and abundance of that host can be used to develop risk maps, which show regions most vulnerable to invasion.
Risk maps can be helpful before an invasion actually occurs. For example, the oak splendor beetle is native to Europe and has not been detected in the U.S.; however, it is related to the emerald ash borer, and could potentially decimate oaks. The risk map developed for the oak splendor beetle shows that parts of the Southern Appalachians would be highly susceptible while the Midwest is at little to no risk.
New pests and pathogens continue to be introduced into the U.S., most often through live plant imports and wood packing material. A new review study co-authored by SRS research forester Thomas Holmes suggests that stronger measures to prevent new infestations may be necessary. The review was published in the journal Ecological Applications, and lists several options for strengthening the defenses against pest arrival and establishment including measures taken in exporting countries, measures ensuring that pests are not hidden in plant shipments or packing material, increasing inspection at ports of entry, and enhancing quarantine, surveillance, and eradication programs.
Minimizing new invasions is critical, but an overwhelming number of non-native pests are already established in the U.S. For these pests, FIA data can help guide management responses in infested areas. “Having data on host distribution greatly increases our understanding of the potential and realized impacts of invasive species,” says Vogt. “FIA data have tremendous value for actions involving prioritization of treatment areas, rapid response to new infestations, and monitoring success over the long-term.”
For more information, email James Vogt at firstname.lastname@example.org.