How do invasive species move from their natural range to new, distant places?
There are many pathways of introduction that move species from their natural range to new, distant places. Most introductions are the result of human activities. Some introductions, such as common carp, buckthorn, and purple loosestrife, were intentional and have caused unexpected damage. Many exotic introductions are unintentional. Species are carried on barges, boats and trailers, animals, vehicles, commercial goods, packing materials, produce, footwear or clothing, and in ballast water of ships. Ships take on ballast water in other countries for stability during the ocean crossing. This water is pumped out when the ships pick up their loads in Great Lakes ports. Many of the species, such as zebra mussel, ruffe, and spiny water flea arrived in the Great Lakes this way. But they are now being spread throughout the continent’s interior in and on boats and through other recreational activities.
