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Pathways

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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

Michigan Department of Agriculture and Rural Development.

The Michigan Department of Agriculture and Rural Development (MDARD) is proposing an Exterior Firewood Quarantine (PDF | 192 KB) to prevent the introduction of unwanted plant pests and diseases into Michigan. Public comments on the proposal are due by Friday, November 19, 2021. Over 140 pests and diseases can be moved by firewood, including Asian long-horned beetle, mountain pine beetle and spotted lanternfly. These pests are not known to exist in Michigan but could be accidentally brought into the state by travelers transporting firewood.

Members of the public interested in providing feedback on this proposed quarantine can submit their comments to Mike Bryan, MDARD Export and Compliance Specialist by emailing BryanM@Michigan.gov. The deadline for comments is Friday, November 19, 2021. Additional information is available at Michigan.gov/Invasives and on MDARD's plant pest quarantine webpage.

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.

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.

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.

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 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.

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.

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.

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.

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. Or, to display all related content view all resources for Pathways

Council or Task Force
Aquatic Nuisiance Species Task Force.

The purpose of pathway risk analysis is to provide scientific analyses and policy recommendations in support of U.S. National Invasive Species Council’s Management Plan. Developed jointly by the Aquatic Nuisance Species Task Force (ANSTF) and National Invasive Species Council (NISC) Prevention Committee via the Pathways Work Team.

Note: This guide only applies to existing unintentional, man-made pathways

Georgia Invasive Species Task Force.

Washington State Recreation and Conservation Office. Washington Invasive Species Council.

Partnership

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.

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.

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.

Nature Conservancy.

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

Nature Conservancy.

The Firewood Outreach Toolbox includes a quick reference list of customize-ready outreach materials, targeted groups outreach list, videos, and logo use instructions.
See also: Outreach resources for professionals related to Forest Pest and Pathogens

Ontario's Invading Species Awareness Program (Canada).

Northeast Marine Introduced Species.

Local Government Aquatic Invasive Species Toolkit.

The primary challenge associated with invasive species ecology is management of introduction vectors. This resource illustrates the framework used to describe invasive species pathways and threats, including the primary pathways of introduction as well as the techniques commonly used to manage the threats, and the priorities for protection from threats. The framework includes 10 primary pathways of introduction: Air transportation/cargo, water transportation, land transportation, items used in shipping, travel tourism/relocation, plant pathways-plant trade, food pathways, non-food animal pathways, non-food animal, other aquatic pathways, natural spread, and ecosystem disturbances.

International Government

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
Alaska Department of Fish and Game.