farming has introduced many species into new areas where they would not naturally be found
some are crop or livestock species that have colonised the surrounding area and become pests, others are pests that have been introduced accidentally such as the late blight fungus of potato and tomato crops
biological control species
biological control can be used to control pests instead of using pesticides, which should reduce environmental damage
however, introducing non-indigenous species can cause problems
introduced predators may eat other species as well as the pests
