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Transportation agencies manage approximately 12 million acres of land in transportation rights-of-way. Vegetation management therefore is a primary activity of department of trans- portation (DOT) maintenance forces in all 50 states, Puerto Rico, and the District of Colum- bia, as well as for local highway departments across the country. Vegetation management can involve significant department staff and staff time, and the battle against invasive species and their effects on the aesthetic and natural environments is requiring increasing time and resources. Vegetation management affects transportation systems, public health, the econ- omy, and natural environments. As transportation corridors for plant and animal invasives carried by traveling vehicles, highways cross geologic barriers that previously prevented the spread of species. Consequently, transportation corridors are a factor in the spread of and loss of natural habitat, the top two drivers of declining biodiversity. Increased species rarity has been a concern to other agency partners and stakeholders. These pressures and Executive Order 13112, which directs all federal agencies to address invasive species concerns and refrain from actions likely to increase invasive species problems, have made a synthesis of existing practice for controlling invasive species more urgent than ever before. This synthesis reviews federal, state, and regional approaches; prevention, early detection, and rapid responses; identification of aspects of operations and risks; statewide inventories; and information management. In particular, this report synthesizes the state of the practice in developing Integrated (Roadside) Vegetation Management, along with physical, chemical, biological, and cultural control mechanisms. The synthesis also covers DOTsâ organizational approaches, staffing, training, and partnerships for invasive species control, along with resources for transportation agencies. It reports on the extent to which DOTs are identifying actions that affect the spread of invasive species, preventing introduction, tracking status and locations of invasives in a timely and ongoing manner, controlling found populations, restor- ing invaded habitats, conducting research, and sharing lessons learned. DOTs surveyed and interviewed for this study commented that Executive Order 13112 has helped increase awareness of and efforts to control invasive species. Transportation agencies have begun performing species surveys on construction projects; controlling infestations; and revegetating with native, lower maintenance species. Coordination among environmental, design and landscape architecture, and construction staff is on the upswing, addressing environmental impacts and eradication and control of invasive species before, during, and after construction. DOTs are taking a variety of steps to share information across division areas and pro- fessional specialties, address cross-cutting needs, and take a more integrated approach to invasive species control. Information is often exchanged informally. Chief among the more formal approaches is the development of organization-wide and district-specific integrated vegetation management plans. Geographic information systems enable the locations of weed patches to be stored digitally, and allow treatments to be tracked, automatically administered in some cases, and assessed over time. Highly effective, lower tech commu- nication mechanisms such as posters and laminated illustrations of various top priority weeds are common as well. DOT landscape architects and roadside managers have also SUMMARY CONTROL OF INVASIVE SPECIES
developed session topics at statewide annual environmental, construction, and mainte- nance meetings. Training of agency employees and contractors has been a notable key to success. Inadequate funding is the primary obstacle faced by state DOTs and others trying to con- trol invasive species. Control efforts tend to be highly fragmented. Statewide roadside inventories for invasive species have been undertaken by 20% of DOTs to assess what needs and challenges there are and the effectiveness of treatments over broader periods of time and space. However, many DOTs say that they are unlikely to attempt such inventories, with several reporting that they were impeded by lack of templates or guidance on invasive species management. 2