How do Invasive Species arrive and spread?

Résumé

Invasive species can be spread deliberately by people for food, as pets, for economic opportunity, or for planting in the garden. A few species such as the mongoose, were deliberately introduced to try and control other pests, but ended up becoming serious invasive species. Invasive species can be introduced accidently such as attaching themselves on cargo, clothing or equipment used in the field. In the marine environment, invasive species are commonly introduced through the ballast water of ships.