What are invasive species? Species are a kind of creature. Invasive species is a phrase that usually refers to a creature that is not native to the area, but becomes resident there; this is the same as discussing non-indigenous species. Sometimes, however, ecologists use the term invasive species to refer to species that heavily colonize an area, but actually were there in lower numbers before; in this case, the word invasive is referring to the high populations of that species. You have to read carefully to know which definition is meant.
There’s another related term: introduced species. Synonyms for “introduced” are non-indigenous, alien, and exotic. An introduced species lives outside its normal distributional range, and arrived because of human intervention.
The pictures show a species of duck called Muscovy duck. Its scientific name is Cairina moschata. The Muscovy* duck species is native to Mexico and Central and South America. Biologists say that the farthest north wild Muscovy ducks range is along the southeast Texas border. Any Muscovy ducks here in Georgia are considered feral populations. Feral populations are escaped domesticated or captive creatures. Muscovy ducks are a non-migratory species. This specimen resides (year-round) in Atlanta’s Piedmont Park.
So, some questions. Are the trees, shrubs, and plants around your county courthouse (or school) native species? Are they introduced species? Are they invasive species? And, are human beings an invasive species? Are human beings in North America invasive?
* The word Muscovy means “from Moscow,” but these birds are not from Moscow; they’re not even from the Old World. The explanation for this term is disputed, but is discussed at length in this Wikipedia entry.