There are some good examples of how these polluters work. The water hyacinth of South America is choking lakes in China and Africa. Tree snakes from Papua New Guinea are busy eating up bird varieties in the country of Guam, which is quite far away. Tiger mosquitoes from Asia are busy biting Americans.
Suddenly, a lot of things become clearer. Like why the customs officials in many foreign countries prevent you from bringing in a small plant, or a decorative item made of wood that is in its natural form?They tell you that its in the rules.
They have these rules because they know that these varieties of plants that are special to specific places have the power to spread new diseases among native plants and animals. They are called biological polluters and they always create problems in places where they do not belong. They could be special varieties of plants, bugs or even animals.