Scientist Names Top Five Invasive Plants Threatening Southern Forests in 2009

U.S. Forest Service Southern Research Station (SRS) Ecologist Jim Miller, Ph.D., one of the foremost authorities on nonnative plants in the South, today identified the invasive plant species he believes pose the biggest threats to southern forest ecosystems in 2009.

“Cogongrass, tallowtree, and Japanese climbing fern are among the fastest moving and most destructive nonnative plant species facing many southern landowners this year,” said Miller. “Rounding out the top five invasive species that I’m very concerned about would be tree-of-heaven and nonnative privets. While our forests are besieged by numerous invasive plants, these and other nonnative species present serious financial and ecological threats to the South and its forests in 2009.”

Nonnative species often out-compete native forest plants and may degrade forest productivity, wildlife habitat, recreational values, and water quality. Invasive species also greatly increase expenses as public and private land managers work to combat their spread and deal with their effects (such as increased wildfire risk and severity).

Nonnative plants can be introduced and spread by wildlife or through other natural means. Humans also spread invasive species by planting them in their gardens and yards and by seeds hitchhiking on their clothes. Additionally, tractors and mowers used in multiple locations without being cleaned often spread nonnative plants.

In an effort to inform forest managers, landowners, and others about where the most threatening invasive plants are in the South and to help them prepare for these threats, Miller collaborated with SRS Forest Inventory and Analysis (FIA) scientists to develop maps showing the spread, county-by-county, across the Southeast of more than 30 of the most serious nonnative plant species. The invasive plant data were collected on FIA plots throughout the southern United States in cooperation with State forestry agencies. In partnership with the University of Georgia’s Center for Invasive Species Science and Ecosystem Health, SRS researchers recently posted the maps and occupation levels online.

Maps posted at http://www.invasive.org/fiamaps/acres.cfm show the number of acres in a county covered by each nonnative species. Maps posted online at

http://www.invasive.org/fiamaps/percent.cfm show the percent of subplots analyzed in a county that have each invasive species. A spreadsheet found at
http://www.invasive.org/fiamaps/summary.pdf shows the total acreage of 33 invasive plant species in 12 Southeastern States (data for eastern Oklahoma is missing as SRS FIA just

completed this part of the State’s inventory this month). Users can access the maps and spreadsheet via http://www.invasive.org/fiamaps/. Current plans are for researchers to update the information annually.

Miller hopes government agencies, forest managers, natural resource professionals, landowners, students, and others will use the information to help combat the spread of nonnative plant species in southern forest and grassland ecosystems.

Details on the five invasive plants mentioned above can be found online via: http://www.srs.fs.usda.gov/pubs/gtr/gtr_srs062/. The Web page features Jim Miller’s book titled Nonnative Invasive Plants of Southern Forests: A Field Guide for Identification and Control, published in 2003. Request a copy by e-mail at srspubqueue@fs.fed.us or by calling 828-257-4830.

Based in Auburn, AL, Miller is a scientist in the SRS Insects, Diseases, and Invasive Plants of Southern Forests unit.