An official website of the United States government

The .gov means it’s official.
Federal government websites always use a .gov or .mil domain. Before sharing sensitive information online, make sure you’re on a .gov or .mil site by inspecting your browser’s address (or “location”) bar.

This site is also protected by an SSL (Secure Sockets Layer) certificate that’s been signed by the U.S. government. The https:// means all transmitted data is encrypted  — in other words, any information or browsing history that you provide is transmitted securely.

You are here


Prevent the Pathway for Invasive Species
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.

The best way to fight invasive species to prevent them from occurring! Learn more about How They Spread to help stop them from USDA's Animal and Plant Health Inspection Service Hungry Pests outreach campaign.

Examples of ways invasive species spread include:

  • Agricultural materials
  • Aquaculture farming
  • Ballast water and shipping
  • Classroom or science lab (escapes or introductions)
  • Firewood
  • Fishing gear
  • Food trade and its packing material
  • Fouled hulls of commercial and recreational vessels
  • Internet sales
  • Moving
  • Outdoor gear (hitchhikers on boots, clothes, and camping equipment)
  • Passenger baggage
  • Pets (unwanted or escaped)
  • Plants and plant parts (escaped or disposals)
  • Recreational boats
  • Recreational vehicles (RVs)

Back to top


  • 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.

Selected Resources

The section below contains selected highly relevant resources for this subject, organized by source. To view all related content for this subject, click on "View all resources for subject" in the top left of this page.

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

Washington Invasive Species Council.


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.

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.

Northeast Marine Introduced Species.

Federal Government

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.

State and Local Government

Alaska Department of Fish and Game.