Management of invasive vegetation in the right of way increasingly impacts state DOT budgets. Invasive species are those non-natives introduced from another region or country. Transported to a new location, such species left behind their natural competition and began to crowd out native species and natural communities, leading to declining diversity, species rarity, agricultural impacts, and management problems. The large majority of non-native species—those occurring in locations beyond their known historical natural ranges and/or brought in from other continents, regions, ecosystems, or habitats-- do not pose a threat to the natural or human systems in which they are introduced; however, a small percentage of non-native species that do establish have the potential to become invasive and to cause significant economic, environmental, and human health consequences.[N] After introduction in a new environment, invasive species may establish easily and quickly, compete aggressively, and grow rapidly, presenting a threat to native species and habitats.

Executive Order (EO) 13112, "Invasive Species" defines invasive as "alien (non-native) species whose introduction does or is likely to cause economic or environmental harm or harm to human health."[N] Invasive species can be plants, animals, and other organisms (e.g., microbes). As transportation corridors enable people and vehicles to move from place to place, highways have become pathways or vectors for the spread of invasive. Construction ground disturbance also has the potential to reduce native species viability if invasive species are not managed prior to or doing construction, non-infested topsoil is not saved, or inadequate attention is given to revegetation with native species.

DOTs driving concerns and objectives in controlling invasive species include cost efficiency, reducing herbicide use, protecting rare or threatened species, and carrying out formal roadside vegetation management plans, and even pavement preservation.[N] Many DOTs were quite vocal about the obstacles confronting control of invasive species. For many, a simple lack of resources -both dedicated funding and dedicated personnel- lie at the heart of insufficient invasive species control. As NYSDOT stated, "[c]urrently, staffing and funding for invasive species management must compete against other priorities for the same staff time and funds – dedicated line items and a separate funding source would be a great benefit." Fifty-three percent of responding DOTs cited lack of state funds as an obstacle in invasive species control. Fifty percent cited a lack of control over lands adjacent to the ROW. Thirty-eight percent said limited federal highway funds were an obstacle to invasive species control. In addition states have varying definitions of invasive species and little legal impetus or guidance for addressing invasive species control. Many states' laws still only address noxious weeds identified for agricultural purposes. Thirty-five percent of responding DOTs cited differing priorities of federal, state and local agencies as obstacles to invasive species control. Inadequate or incomplete inventories of invasive, as well as means to track those identified remain obstacles for others.

Lack of templates or guidance on invasive species management is an obstacle for 33 percent of responding DOTs, while finding suitable native ground covers and the perception of native grasses as being difficult or slow to establish are issues for 28 and 30 percent, respectively.

Other obstacles cited by individual DOTs include the additional cost imposed by best practices such as equipment washing, the difficulty of monitoring such measures, the lack of specific guidelines or policies on a programmatic scale, poor and compacted soils, disturbed and degraded roadsides, and lack of an easy (commitment) tracking system for segments of ROW that come under federal funding for purposes of compliance with E.O. 13112 (with status easily accessible to maintenance personnel as projects close and landscaping and maintenance projects start and close). Getting the right information to the right people was a concern for some DOTs. As one put it, the problem is "[l]ack of communication, lack of training for contractors and overall lack of awareness in the organization, especially in that this is a serious issue." Others lack good training materials or management guidelines. DOTs also noted that access to information about the costs and benefits of treating invasive species could bolster their ability to get resources allocated to address the problem. Some of the key available information in this area is described or referenced below, by weblink if available. NCHRP Synthesis project 36-05 will go into greater detail on these topics.

In the United States, nonindigenous species do more than $130 billion a year in damage to agriculture, forests, rangelands, and fisheries, as estimated by Cornell University biologists.[N] Managers on Department of the Interior and other public lands, as well as the private sector, rank invasive species as their top resource management problem.[N] Estimates of current infestation on federal lands are in the range of 35 million acres (around 5 percent) on BLM lands alone;[N] however, at the estimated rate of expansion (5-15 percent/annually), the acreage infested doubles roughly every nine years.[N] The threat posed by this rate of expansion is enormous, in terms of lost natural resource values, economic production, and cost. By 2040, without substantial investment to stop the spread of such weeds, over 50 percent of federal land could be infested.[N] For DOTs, increasing roadside management costs are felt in terms of additional mowings, herbicide inputs, and labor, as well as the pressure to respond to public complaints.

Former Secretary of the Interior, Bruce Babbitt, noted that "[t]he invasion of noxious alien species wreaks havoc on America's environment and economy that is matched only by damage caused by floods, earthquakes, mudslides, hurricanes, and wildfire."[N] Introduced organisms are the second greatest cause, after habitat destruction, of species endangerment and extinction worldwide.[N] Invasive species are a factor in the decline of 49 percent of all imperiled species.[N] According to an Office of Technology Assessment study, just 79 of these non-native species cost the American public some $97 billion in damages to natural resources and lost industrial productivity during the 20th century.[N] These costs arise from a variety of factors: [N]

• Contamination or competition with crops.
• Decrease in forage value of rangeland and pastures.
• Displacement of valuable wildlife habitat and disruption of food chains.
• Elimination of waterfowl migration stops.
• Reduction in property values and ability to acquire loans.
• Alteration of ground water reserves.
• Change in aesthetics of the landscape and degradation of natural heritage and educational value.
• Increased fire threats.
• Compromise of roadside visibility and safety.
• Attraction of wildlife to roadside.
• Additional costs of roadside maintenance.

The above costs are rising as invasive plants spread into another estimated 4,600 acres daily.[N] In a 2002 report entitled, Invasive Species: Clearer Focus and Greater Commitment Needed to Effectively Manage the Problem, the U.S. General Accounting Office (GAO) found that most economic estimates do not consider all of the relevant effects of nonnative species or the future risks that they pose, but that more comprehensive analysis could help decision makers make better resource allocations; i.e., allocate more resources to the task.

Other efforts by states, associations, and scientific entities to begin to document cost-benefit data for invasive species control include: [N]

• WSDOT Comparison of Roadside Maintenance Practices - Impacts of Herbicide use on Cost and Results . Management without herbicides costs roughly double.[N]
  
  
• Northeastern States' Costs of Managing Invasive Species , compiled by Ray Bouchard, Maine Department of Environmental Protection.
  
  
• Costly Interlopers: Introduced species of animals, plants and microbes cost the U.S. $123 billion a year , Scientific American (Feb 15, 1999).
  
  
• Combating the Economic and Environmental Devastation from Invasive Species Western Governors' Association (Dec 2000).
  
  
• Economic and Environmental Threats of Alien Plant, Animal, and Microbe Invasions ( Cornell University, Ecosystems and Environment 84 (2001) 1–20
  
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• Economic Dimensions of Invasive Species Edward A. Evans, Choices Magazine: Food, Farm, and Resource Issues (Jun 2003).
  
  
• Economic Impact of Invasive Species to Wildlife Services' Cooperators David L. Bergman, et al., Proceedings of the Third National Wildlife Research Center Special Symposium: Human Conflicts with Wildlife: Economic Considerations.
  
  
• Nonindigenous Aquatic and Selected Terrestrial Species of Florida: Status, Pathway and Time of Introduction, Present Distribution, and Significant Ecological and Economic Effects, James A. McCann, Lori N. Arkin, James D. Williams, National Biological Service, Gainesville, Florida.
  
  
• Noxious Weed Cost Share Program and ISDA 2002 Cost Share Program Accomplishments, Idaho State Department of Agriculture.
  
  
• West Nile Virus Economic Impact, Louisiana, 2002 , Centers for Disease Control and Prevention, Emerging Infectious Diseases, Vol. 10, No. 10 (Oct 2004). The 2002 Outbreak of West Nile Virus Cost Louisiana $20 Million
  kplctv.com/AP (Sep 28, 2004).
  
  
• Potential Economic Losses Associated With Uncontrolled Nutria Populations in Maryland's Portion of the Chesapeake Bay , Maryland DNR (Nov 2, 2004).
  
  
• The Impact of Knapweed on Montana's Economy , North Dakota State University Agricultural Experiment Station (Jul 1996).
  
  
• Estimating Net Losses in Recreation Use Values from Non-Indigenous Invasive Weeds University of Nevada- Reno, Cooperative Extension, Special Publication SP-03-10.
  
  
• The Economic Costs of Delaying Invasive Weed Control: An Illustration based on Nevada's Tall Whitetop Initiative , University of Nevada-Reno, Cooperative Extension, Special Publication SP-01-08.
  
  
• The Estimated Costs of Treating Invasive Weeds in Elko County, Nevada
  University of Nevada-Reno, Cooperative Extension, Fact Sheet FS003-41.
  
  
• Economic Analysis of Containment Programs, Damages, and Production Losses From Noxious Weeds in Oregon , The Research Group, Corvallis, Oregon, for Oregon Department of Agriculture, Plant Division, Noxious Weed Control Program (Nov 2000).
  
  
• Impacts of Aquatic Nuisance Species Within the State of New York
  New York Sea Grant.
  
  
• Fire Ants Cost Texans Millions, Texas A&M University , Department of Entomology (Apr 21, 2000).
  
  
• Invasive Non-native Species: Background and Issues for Congress (revised Nov 25, 2002) Washington, DC: Congressional Research Service.
  
  
• Riparian Impacts - Invasive plants damage green zones along rivers and streams. Montana Weed Control Association.
  
  
• Rocky Mt Research Station: Foreign Weeds Feed Western Fires . Newspaper article on the problem of invasive plants and possible solutions. From the US Forest Service.
  
  
• The Spread of Invasive Weeds in Western Wildlands: A State of Biological Emergency, The Governor's Idaho Weed Summit . From the Bureau of Land Management.
  
  
• Weed Control on Conservation Reserve Program (CRP) Acres . Establishing perennial grasses on former cropland presents a challenge. Weed control can be accomplished with herbicides, tillage, burning, mowing, and crop competition. The key to weed control is timeliness. From the University of Nebraska Lincoln.
  
  
• Invasive weeds in rangelands: Species, impacts, and management . –Rangeland and pastures comprise about 42% of the total land area of the United States. This abstract describes the effects of found more than 300 rangeland weeds in the United States, which cause an estimated loss of $2 billion annually in the United States impacting the livestock industry, interfering with grazing, poisoning animals, increasing costs of managing and producing livestock, and reducing land value. Weed Science Society of America.
  
  
• Knapweed - Its cost to British Columbia (B.C.) - Several aspects of how knapweed (both diffuse knapweed, Centaurea diffusa, and spotted knapweed, Centaurea biebersteinii) infestations are causing major environmental deterioration and loss of beef production in the southern interior of British Columbia. B.C. Ministry of Agriculture, Food and Fisheries.

Federal funds with regard to construction and maintenance may be used for new and expanded invasive species control efforts under each state DOT's roadside vegetation management program, including:

• Statewide, right-of-way inventories of vegetation that map existing invasive plant infestations.
• Inspection and cleaning of construction equipment.
• Commitments to ensure the use of invasive-free mulches, topsoils and seed mixes.
• Eradication strategies to be deployed should an invasion occur.

Multiple Executive Orders have directed federal agencies to address invasive species concerns and refrain from actions likely to increase invasive species problems. It also directs agencies to "provide for restoration of native species and habitat conditions in ecosystems that have been invaded." FHWA's implementing guidance specifies that: [N]

• Federal funds cannot be used for construction, revegetation, or landscaping activities that purposely include the use of known invasive plant species as listed by some states or the National Invasive Species Council.
• NEPA analyses require determinations of the likelihood of introducing or spreading invasive species and a description of measures being taken to minimize their potential harm.

A number of DOTs have started completing invasive species surveys for all projects (state and federal) with ground disturbing activities. If weeds are found and adjacent lands are federal, the DOT coordinates with that agency for more effective control of invasive species. Special mitigation measures to prevent the spread of weeds found and to prevent the introduction of invasive species are incorporated into NEPA documentation and contract specifications. Coordination among environmental, design/landscape architecture, and construction staff is on the upswing, addressing environmental impacts and eradication and control of invasive species during and after construction. At New York State DOT (NYSDOT) and Utah DOT (UDOT), for example, the departments are including invasive species in NEPA decision-making processes, documenting potential environmental impacts, and listing appropriate best management practices as mitigation commitments for all projects that have the potential to spread or introduce listed weeds.