Nonnative species are also referred to as introduced, exotic, or alien species. The National Park Service defines nonnative as species that occur in a given place as a result of direct, indirect, deliberate, or accidental actions by humans. Plant species that are brought into an area as food, fiber, or ornamental landscape plantings can "jump the fence" and become established in the wild.
Likewise, nonnative animal species can be introduced into an area deliberately, for agricultural use or fish stocking; or by "hitching a ride" on objects like boat hulls and outboard motors. Many species find their way to new locations in crop seed, soil or nursery stock.
Although many introduced species have had a negative impact on our society, primarily in agriculture, these species would not have evolved with the native species and therefore are not a natural component of the ecological system. In extreme cases, invasive nonnative species can displace native species, thereby degrading the integrity and diversity of native communities. Alien species can also become pests, such as Asian lady beetles and zebra mussels.
Silver and Bighead (Asian) Carp, AKA silverfin - These plankton feeders were imported to clear the water in aquaculture and settling ponds. Escaped, they have flourished and spread, taking resources form native species. They have become popular targets for bowfishing and, as an entirely different species from the common grass carp, are excellent eating. Help control invasive species; eat Silverfin!
Zebra Mussels - Accidentaly imported to the Great Lakes and lower Mississippi in the ballast water of cargo ships, these shellfish cause tremendous damage to both natural systems and man-made structures. Their large colonies remove vital plankton from the food chain, smother native shellfish, clog water intakes and boat motors, and encrust boat docks and other structures. Dead, their razor-sharp shells make beaches hazardous. There is no known means of eliminating these destructive pests once they have become established.
These mussels are not currently present in the Wild & Scenic designated stretches of the Missouri. They can only move upstream or overland by hitchhiking on boats and trailers. For this reason, it it essential that any and all boats and trailers coming from other waterways be properly washed and/or dried before launching in uncontaminated waters.
There are currently about 8 nonnative plant species being targeted for action within the MNRR that are of high management concern. These include:Purple loosestrife - although beautiful, is a noxious weed, well known for its capacity rapidly to invade wetlands, replace native vegetation and dominate those habitats at the expense of turtles, birds and other animals.
- Salt cedar - also known as Tamarisk, it is a deciduous shrub or small tree. It can absorb 200 gallons of water per day, giving heavy infestations the ability to dry up creeks and small lakes.
- Russian olive
- Canada thistle
- Leafy spurge - a noxious weed that has driven out and taken over from native species.
- Phragmites - A tall, invasive grass.