How Do They Get Here?

There are two ways that invasive species move into an area, these are referred to as pathways, the first are natural pathways and the second are human created pathways.

Natural Pathways

Natural pathways are pathways that humans have no control over they include birds and wind carrying seeds, and water carrying animals.

Human Pathways

These pathways are the pathways that people concerned with invasive species hope to control. Some human pathways include:
Aquaria - http://www.wise.wa.gov/pathways/aquaria.aspx
Boats - http://www.wise.wa.gov/pathways/boats.aspx
Food/Medicines - http://www.wise.wa.gov/pathways/foodandmedicinals.aspx
Travel - http://www.wise.wa.gov/pathways/travel.aspx
Vehicles - http://www.wise.wa.gov/pathways/vehicles.aspx
Gardens - http://www.wise.wa.gov/pathways/gardenornamental.aspx

Further Reading

Washington State's Invasive Species Council's page on pathways with links to other organizations information about pathways.
http://www.invasivespecies.wa.gov/how_do_they_get_here.shtml

The Washington Invasive Species Education site's page on pathways, source for the human pathways links; this site includes more pathways, and more information on specific pathways, as well as examples of species that have entered Washington through various pathways.
http://www.wise.wa.gov/pathways/index.aspx