What are Invasive Species?

24 June

What are Invasive Species?

Native, indigenous, non-native, exotic, invasive, non-native invasive.  These are some of the many ways that the conservation community describes the origins and status of plants, animals, insects, reptiles, amphibians and other organisms in our natural communities.  However, the similarity of these terms and sometimes subtle differences between them often creates confusion.  It is our hope in this post to make these blurred lines a little clearer with a breakdown of the individual terms. 

Native Species – A species found in the particular region or ecosystem in which it evolved.  

While this definition seems simple it does not tell the whole story.  A plant that is considered an “Illinois native” may not be native across the state, only a certain part or parts.  For example, the shortleaf pine (Pinus echinata) is native to Illinois.  However, before it was propagated and planted across the state, it was only known to naturally occur at LaRue Pine Hills Research Natural Area in Union County and Piney Creek Ravine Nature Preserve on the Randolph/Jackson County line.  

Indigenous Species – This term is synonymous with “native species.”  

Non-Native Species – Species that have been introduced, accidentally or intentionally, outside of their native range.  

Non-native status does not always carry a negative connotation, it is believed that only 1 in 1,000 non-native species will become invasive when introduced to new ecosystems.  Species native to the United States can be non-native within the country depending on where they are found.  For example, the loblolly (Pinus taeda) is native from southern New Jersey down to Florida and west to Texas but is considered non-native in Illinois and other states where it is commonly found.  

Exotic Species -These are species found outside of their native continent.  

Just like non-native species, exotic species are not necessarily a bad thing.  Many of the fruit and vegetables we grow in our gardens and on farms are exotic, along with flowers, shrubs and trees that adorn our lawns.   

Invasive Species – These are species that are not native to the ecosystem in which they occur and cause significant ecological degradation, economic damages or risks to human health.  

Species that become invasive often lack predators and/or diseases outside of their native range, have special traits that allow them to out-compete native species, and/or fill empty or specialty niches within an ecosystem.  In southern Illinois, invasive species impact native ecosystems through losses or changes in habitat, biodiversity, species abundance, ecosystem productivity and economic productivity.  Forests, grasslands, wetlands, glades, barrens and other native communities are all imperiled by current and future invasion.  

Non-Native Invasive Species – This term is synonymous with “invasive.”

Hopefully you now have a better understanding of what these different terms mean.  If you wish to learn more about invasive species in southern Illinois, here is list of the most common invaders:

  • Amur honeysuckle (Lonicera maackii)
  • Autumn olive (Elaeagnus umbellata)
  • Callery (Bradford) Pear (Pyrus calleryana)
  • Chinese yam (Dioscorea oppositifolia)
  • Common reed (Phragmites australis)
  • Garlic mustard (Alliaria petiolata)
  • Japanese chaff flower (Achyranthes japonica)
  • Japanese honeysuckle (Lonicera japonica)
  • Japanese hops (Humulus japonicus)
  • Japanese stiltgrass (Microstegium vimineum)
  • Kudzu (Pueraria montana)
  • Multiflora rose (Rosa multiflora)
  • Oriental bittersweet (Celastrus orbiculatus)
  • Princess tree (Paulownia tomentosa)
  • Reed canary grass (Phalaris arundinacea)
  • Sericea lespedeza (Lespedeza cuneata)
  • Tree-of-Heaven (Ailanthus altissima)
  • Winged burning bush (Euonymus alatus)
  • Wintercreeper (Euonymus fortunei)