The Invasion of Southern Forests by Nonnative Plants

Key Findings from the Southern Forest Futures Project Technical Report

Princesstree (Paulownia tomentosa), invades widely after wildfire, timber harvesting, and other disturbances. Photo by Leslie Mehrhoff, courtesy of Bugwood.org.
Princesstree (Paulownia tomentosa), invades widely after wildfire, timber harvesting, and other disturbances. Photo by Leslie Mehrhoff, courtesy of Bugwood.org.

The Southern Forest Futures Project (SFFP) started in 2008 as an effort to study and understand the various forces reshaping the forests across the 13 states of the Southeast. Chartered by the U.S. Forest Service Southern Region and Southern Research Station along with the Southern Group of State Foresters, the project examines a variety of possible futures and how they might shape forests and their many ecosystems and values.

Invasive plants increasingly infiltrate southern forests, eroding landscapes and replacing native communities while degrading critical human-sustaining ecosystems. The SFFP technical report chapter on nonnative invasive plants summarizes information for 56 of the most damaging trees, shrubs, vines, grasses, and forbs currently invading forests, pastures, rights-of-way, orchards, grasslands, wetlands, and yards in the South. 

Key findings from the chapter:

  • Invasive plants continue to escape into and spread through southern forests to eventually form exclusive infestations nd replace native communities to the detriment of forest productivity, biodiversity, ecosystem services, and human use potential.
  • Over a 300-year period, invasive plants have been increasingly imported into the South, despite public policies and warnings by professional ecologists and plant experts of long-term irreversible ecosystem damage.
  • Approximately 9 percent of southern forests — or about 19 million acres — are currently occupied by one or more of the 300 invasive plants in the region.
  • The invasion process is accelerated by greater forest disturbance, fragmentation, parcelization, and urbanization needed to accommodate and support an increasing population and is by climate warming.
  • The annual spread of invasive plants in southern forests is conservatively estimated at 145,000 forested acres.
  • Given the current occupation and spread of invasive plants and the increasingly common infestations by multiple species, eradication appears only probable on specific lands unless awareness and strategic programs are greatly enhanced.
  • Over a 20-year period, research has developed effective control treatments and integrated approaches that can eradicate or replace invasive plants, while a more robust, coordinated, and focused effort will be required to stem and turn the tide of invasion.
  • Model projections show high-threat invasive plants have not reached their potential range or density limits within the region under current conditions. A predicted warming climate will permit northward range extensions for some, while range extensions can be restricted by a simultaneous drier climate.
  • Increased occupation by invasive plants would diminish the variety and abundance of current wood-based products from the “wood basket” of the United States. Some invasive species may find use in biomass and composite products if harvesting and processing become more efficient.
  • Most plants escaping into southern forests have been imported, hybridized, sold, and planted for yard and garden beautification, soil stabilization, wildlife habitat enhancement, and livestock production.
  • Stricter controls for importing species are pending, but their effectiveness will be hampered as long as garden centers continue to market invasive plants as ornamentals.
  • Limiting the degree of occupation and impact depends on the development of adaptive management programs and actions that are coordinated across political boundaries and engage all ownerships. Piecemeal and splintered actions by agencies and ownerships, if continued, cannot dwarf the destructive impacts of this invasion.
  • Public awareness campaigns, cooperative spread abatement networks, collaborative programs of detection and eradication, dedicated research and extension programs, and employment of new land restoration options have been found to slow the spread of invasive plants and prevent them from destroying critical habitats.

Access the Southern Forest Futures Project Technical Report.

 Access the Summary Report of the Southern Forest Futures Project.

 Access the latest publications by SRS scientists.

 

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