What is an alien or introduced species?
When a species is planted or ends up in a new ecosystem, it is considered “introduced.” Species naturally change their ranges slowly over time, but it is not these natural events that concern us. Most of the introductions that result in invasive species are human caused. In some cases, we deliberately introduce species. Examples of this include garden ornamentals, range forage or food for cattle, animals and insects used to control other organisms (particularly in agriculture), and plants used for erosion control and habitat enhancement for wildlife. Other species are introduced accidentally on imported nursery stock, fruits, and vegetables, in ship ballast waters, on vehicles, in packing materials and shipping containers, through human-built canals, and through human travel. Sometimes you will see alien species referred to as exotic, introduced, or non-indigenous species. The problem with these names is that they only refer to the non-native part of the definition. Many exotic or alie
