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Pathways

Pathways of Invasive Plants - U.S. Fish and Wildlife Service

Pathways are the means and routes by which invasive species are introduced into new environments. Pathways can generally be classified as either natural or man-made.

Natural pathways (i.e., those not aided by humans) include wind, currents (including marine debris), and other forms of natural dispersal that can bring species to a new habitat.

Man-made (or human-mediated) pathways are those which are created or enhanced by human activity. These are characteristically of two types:

  • Intentional, which is the result of a deliberate movement of a species by humans outside of its natural range. Examples include the introduction of biological control organisms or the movement of species for the horticultural or pet trade. Intentional introductions as a whole should not be labeled as either good or bad. A specific intentional pathway can only be judged by the positive or negative impact of the specific organisms that are moving along that means.
  • Unintentional, which is the inadvertent movement of species as a byproduct of some other human activity. Examples of unintentional pathways are ballast water discharge (e.g. red-tide organisms), pests and diseases in imported plants, firewood, and other agricultural products (e.g. fire ants), the movement of recreational watercraft (e.g. zebra mussels), and the international movement of people (e.g. pathogens). In these and countless other unintentional pathways, the movement of non-native species is an indirect byproduct of human activities.

For our purposes, the term "vector" is viewed as a biological pathway for a disease or parasite (i.e. an organism that transmits pathogens to various hosts) and is not completely synonymous with the much broader definition of a pathway. The Asian citrus psyllid is an example of a vector of the serious citrus greening disease or Huanglongbing.

Examples of ways invasive species spread include:


Spotlights

  • Antarctica: Invasive Species 'Hitchhiking' on Ships

    • Jan 10, 2022
    • BBC News.

    • Species from around the world that are "hitching a lift" on ships threaten Antarctica's pristine marine ecosystem.

  • Great Lakes Commission Shares Lessons Learned from Fight Against Internet Sales of Aquatic Invasive Species

    • Jul 12, 2022
    • Great Lakes Commission.

    • The Great Lakes Commission (GLC) released a report on the second phase of its work to stop internet sales of aquatic invasive species (AIS) in the Great Lakes region. The GLC initiative, known as the Great Lakes Detector of Invasive Aquatics in Trade (GLDIATR), demonstrated that “web crawling” applications can be used to track the online sale of priority AIS and support the work of AIS researchers, outreach coordinators, managers, and law enforcement officials across the Great Lakes basin.

  • Marine Plastic Pollution Could Contribute to the Introduction of Invasive Species

    • Mar 2, 2022
    • Institut de Ciències del Mar; University of Barcelona (Spain).

    • A new study led by the Institut de Ciències del Mar (ICM-CSIC) and the University of Barcelona (UB) has revealed that marine plastic pollution could contribute to the introduction and transport of non-native species that attach to these particles of anthropogenic origin.

  • IMO-Norad Project to Demonstrate Solutions for Greenhouse Gases and Biosafety

    • Dec 14, 2021
    • International Maritime Organization.

    • A newly signed project is set to provide pilot projects in developing countries in order to demonstrate technical solutions for biofouling management, address the transfer of invasive aquatic species and help reduce greenhouse gas emissions from ships. Biofouling is the accumulation of aquatic organisms on wetted or immersed surfaces such as ships and other offshore structures.

      The project complements the existing Global Environment Facility (GEF)/United Nations Development Programme (UNDP)/IMO GloFouling Partnerships Project, which aims to support its lead partnering and partnering countries to implement IMO's Biofouling Guidelines (PDF | 134 KB).

  • Canadian Minister of Transport Announces New Regulations to Help Prevent Spread of Aquatic Invasive Species in Canada

    • Jun 23, 2021
    • Transport Canada.

    • Canada's coasts and waterways are vital to our environment, livelihoods, and economy, and must be protected. Ballast water, which helps keep vessels stable in the water, can accidentally introduce and spread aquatic invasive species, like the zebra mussel, if released in the water untreated. To further protect Canadian waters, the Government of Canada is taking action to limit the introduction and spread of aquatic invasive species in ballast water. Today, the Canadian Minister of Transport announced the coming into force of the new Ballast Water Regulations to strengthen existing rules for vessels on international voyages and the introduction of new rules for vessels which remain in Canada and on the Great Lakes. These regulations, which replace the Ballast Water Control and Management Regulations, apply to vessels in Canadian waters and to Canadian vessels anywhere in the world. Vessels are now required to:

      • plan their ballast water management and reduce the number of organisms in their ballast water, typically by installing a ballast water management system; and
      • carry a valid certificate, keep records, and be regularly surveyed and inspected. Smaller vessels may follow an equivalent approach tailored to their operations and size.

      For more information, see Managing Ballast Water and Backgrounder: Ballast Water Regulations.

  • Firewood Transport as a Vector of Forest Pest Dispersal in North America: A Scoping Review

    • Feb 2021
    • Cornell University. New York Invasive Species Research Institute.

    • A cozy campfire for summer days, a warm fireplace for winter evenings– the use of firewood is an "established cultural norm". However, moving firewood from place to place can have devastating consequences, as it can spread forest pests that decimate forests to collectively cost an estimated $4.2 – $14.4 billion per year. In order to better address the problem of people moving firewood and vectoring forest pests, Solano and colleagues examined trends and gaps in the existing literature on firewood and human-mediated forest pest movement in North America. The existing literature demonstrates the risk of firewood movement, but fails to address the level of awareness the public has on such risks, or the level of effectiveness of firewood regulations to prevent forest pest spread.

  • Invasive Plants are Still for Sale as Garden Ornamentals, Research Shows

    • Aug 9, 2021
    • University of Massachusetts - Amherst.

    • UMass Amherst study finds that invasive species are widely available due to inconsistent regulation. Results of a new study by ecologists at the University of Massachusetts Amherst show that 1,330 nurseries, garden centers and online retailers are still offering hundreds of invasive plant species as ornamental garden plants. This includes 20 species that are illegal to grow or sell nationwide.

      The study, “Invaders for sale: the ongoing spread of invasive species by the plant trade industry,” published in Frontiers in Ecology and the Environment, shows that existing regulatory and ethical guidelines do not serve to limit the widespread introduction of invasive plants and that more than 60% of the 1,285 plants identified as invasive remain for sale.

  • Using Data to Tackle the Dangerous Mail Pest Pathway

    • Feb 26, 2021
    • USDA. APHIS. Plant Protection Today.

    • The PPQ Mail Interception Dashboard can filter data to show where illegal shipments have been intercepted in the past and plot the locations across the United States. The dashboard will help us to better understand where violations are located; what products are being imported, from where, and how often; and the pathways that illegal packages travel to the United States.

  • Hitchhiking Seeds Pose Substantial Risk of Nonnative Plant Invasions

    • Sep 29, 2020
    • USDA. FS. Southern Research Station. CompassLive.

    • Seeds that float in the air can hitchhike in unusual places – like the air-intake grille of a refrigerated shipping container. A team of researchers from the USDA Forest Service, Arkansas State University, and other organizations recently conducted a study that involved vacuuming seeds from air-intake grilles over two seasons at the Port of Savannah, Georgia. The viability of such seeds is of significant interest to federal regulatory and enforcement agencies, and the project required a shared stewardship approach. Their findings were recently published in the journal Scientific Reports.

      Seeds from 30 plant taxa were collected from the air-intake grilles, including seeds of wild sugarcane (Saccharum spontaneum), a grass on the USDA Federal Noxious Weed List. Federal noxious weeds pose immediate, significant threats to agriculture, nursery, and forestry industries. Although a lovely grass and useful in its native range, wild sugarcane has the potential to join cogongrass, stiltgrass, and other nonnative species that have become extremely widespread in the U.S.

  • New Zealand’s Craft Risk Management Standard for Vessel Biofouling: A Blue-Print for Marine Pathway Management

    • Jul 29, 2020
    • New Zealand Ministry for Primary Industries. Biosecurity New Zealand; National Institute of Water and Atmospheric Research.

    • New Zealand is the first country to implement nationwide regulations to manage risks associated with biofouling on international vessels. The development of this regulation and its implementation can serve as a blue-print for other jurisdictions that are interested in preventing the spread on non-indigenous marine species.

  • Report Lifts Lid on Australia's International Bug Superhighway

    • Apr 15, 2020
    • Australian Invasive Species Council.

    • A new report has identified an international 'bug superhighway' capable of carrying a large variety of environmentally destructive overseas insects into Australia. The study, led by Monash University, rated the environmental harm being caused by 100 of the worst overseas insect species and recommends a string of actions to keep them out of Australia. The most dominant group of invasive insects by far are the hymenopteran insects – ants, bees and wasps – making them the world's most environmentally harmful invasive insect species.

      "Our report found that environmentally harmful bugs, beetles, ants and moths are most likely to hitch a ride into Australia along an international bug superhighway made up of imported plants, nursery material and the timber trade," said report author Professor Melodie McGeoch from Monash University. The report identifies the international trade in cut flowers and foliage as a high-risk pathway for more than 70 of the species studied. Invasive Species Council CEO Andrew Cox said this is the first time Australian and international scientists have comprehensively analysed which invasive insects overseas are doing the most environmental harm and could therefore threaten Australia's natural environment if they breach the nation's borders.

  • Marine Debris as a Potential Pathway for Invasive Species

    • 2017
    • DOC. NOAA. Marine Debris Program.

    • There is mounting concern over the increase in debris in our ocean and the potential for that debris to assist in the spread of non-native species. While the pathways associated with global shipping draw the greatest amount of attention regarding marine invasives, the purpose of this paper is to consider the potential role that marine debris may play in introducing non-native species that may become invasive. This report reviews the scientific literature that exists on the subject and identifies areas where more research is needed.

  • Firewood

    • USDA. Animal and Plant and Health Inspection Service.

    • Whether used to heat your home or build a campfire, firewood is a must-have item for millions of Americans. However, firewood also presents a very real threat to the Nation's forests. Invasive species including the Asian longhorned beetle (ALB), the emerald ash borer (EAB), and gypsy moth can be spread into new areas of the country on firewood.

  • Habitattitude - Animals and Plants in Classroom Education

    • Pet Industry Joint Advisory Council; DOI. Fish and Wildlife Service; DOC. National Oceanic and Atmospheric Administration.

    • Pets in K-12 school classrooms can be valuable teaching assets. Caring for companion animals helps students to relate to species in their natural habitats while fostering a sense of environmental ethics. Provides information for planning for classroom pets, caring the classroom pets after the school year, how to protect the environment, and additional resources.

Selected Resources

The section below contains highly relevant resources for this subject, organized by source.

Council or Task Force
Partnership
  • Neighborhood Watch: Early Detection and Rapid Response to Biological Invasion along U.S. Trade Pathways

    • 2009
    • International Union for Conservation of Nature.

    • This report offers recommendations to improve biosecurity measures at U.S. ports, as well as a possible funding mechanism based upon the polluter-pays principle.

  • Denying Entry: Opportunities to Build Capacity to Prevent the Introduction of Invasive Species and Improve Biosecurity at US Ports

    • 2007
    • International Union for Conservation of Nature.

    • The aim of this report was to identify the resources, strategies, and policies necessary to create, maintain, and make accessible one or more commodity/invasive species databases that EPA and other relevant agencies can apply to trade policy decision-making in a timely and scientifically-based manner.

  • AIM - How Invasions Happen

    • Aquatic Invaders in the Marketplace.

    • The AIM campaign that focuses on providing information and best practices to manage The Organisms in Trade (OIT) pathway. The OIT pathway is one of the main avenues by which non-native aquatic species become established in waterways. Many of the aquatic plants and animals available in the marketplace can negatively impact ecosystems, economies, and public health when introduced to new freshwater habitats. AIM was developed by a collaboration of researchers and outreach specialists led by Illinois-Indiana Sea Grant and the Illinois Natural History Survey.

  • Don't Move Firewood - Emerald Ash Borer Awareness Week Toolkit

    • Nature Conservancy.

    •  Emerald Ash Borer Awareness Week is in May each year. Provides outreach materials for EAB EAB Awareness Week.

  • Don't Move Firewood - Toolbox

  • Great Lakes Detector of Invasive Species in Trade (GLDIATR)

    • Great Lakes Commission.

    • The Great Lakes Detector of Invasive Aquatics in Trade (GLDIATR) is an innovative approach developed by the Great Lakes Commission that uses advanced technology to search the internet for sites where aquatic invasive species can be purchased and shipped to the Great Lakes region. This information can be used by invasive species managers to inform and help target a variety of activities including outreach and education, risk assessment, monitoring and surveillance, and enforcement.

  • InvadingSpecies.com - Pathways

    • Ontario's Invading Species Awareness Program (Canada).

  • Local Government Aquatic Invasive Species Toolkit

    • Pacific States Marine Fisheries Commission. Western Aquatic Invasive Species Resource Center.

    • The purpose of this toolkit is to assist local governments with navigating the regulatory framework associated with high-risk priority aquatic invasive species (AIS). Financial support for the development of this toolkit was provided by the U.S. Fish and Wildlife Service, U.S. Department of Interior, under award #F20AP00238.
      See also: Role of Local Governments in Aquatic Invasive Species Prevention Efforts (National Sea Grant Law Center)

  • National Plant Board Firewood Working Group Guidelines

    • National Plant Board.

    • In an attempt to limit the transfer of pests across state lines in firewood, these guidelines provide information on the process of drafting new or revising current state-based regulations pertaining to firewood, share case studies of states that have already approached firewood quarantines, provide examples of strategies beyond regulation that could enhance a state’s overall response to the firewood pathway, and give selected recommendations or examples within these strategies.

  • Pathways and Prevention

    • Northeast Marine Introduced Species.

International Government
  • Invasive Alien Species in Ireland - Pathway Action Plans

    • National Biodiversity Data Centre (Ireland).

    • With increased movement of people and goods around the world, there is an increased introduction of alien (non-native) species to new areas where they can become invasive. Key to this, is knowing how the invasive species are likely to be introduced and acting to prevent further introductions through those pathways. The purpose Pathway Action Plans is to raise public awareness as well as to prevent unintentional introductions by minimizing the contamination of goods, commodities, vehicles and equipment by IAS, and ensuring appropriate checks at EU Union borders.

State and Local Government
Academic