Definition: Threats from non-native and native plants, animals, pathogens/microbes, or genetic materials that have or are predicted to have harmful effects on biodiversity following their introduction, spread and/or increase in abundance

Exposition: We spent a lot of time talking to experts about the subdivisions and phrasing of this class. They would like to restrict the use of “invasive species” to refer to non-native species to keep things simple for policy makers. They recommended using the term “problematic native species” to refer to native species that have become superabundant or otherwise cause problems. If possible, also record the source of the invasive species and/or conditions that exacerbate their effect.

8.1 Invasive Non-Native/Alien Species

Definition: Harmful plants, animals, pathogens and other microbes not originally found within the ecosystem(s) in question and directly or indirectly introduced and spread into it by human activities

Exposition: We are defining non-native/alien/exotic species as those brought either intentionally or accidentally by humans in the last 10,000 years.


  • feral cattle
  • household pets
  • zebra mussels
  • Dutch elm disease or chestnut blight
  • Miconia tree
  • introduction of species for biocontrol
  • chytrid fungus affecting amphibians outside of Africa

8.2 Problematic Native Species

Definition: Harmful plants, animals, or pathogens and other microbes that are originally found within the ecosystem(s) in question, but have become out-of-balance or released directly or indirectly due to human activities

Exposition: It is a bit of a judgment call as to when a species becomes “problematic” (aka outside its natural range of variation). This category could probably be refined over time.


  • overabundant native deer
  • overabundant algae due to loss of native grazing fish
  • native plants that hybridize with other plants
  • plague affecting rodents

8.3 Introduced Genetic Material

Definition: Human altered or transported organisms or genes

Exposition: Hatchery fish are not necessarily invasive species, but they can upset the gene pool of native fish.


  • pesticide resistant crops
  • hatchery salmon
  • restoration projects using non-local seed stock
  • genetically modified insects for biocontrol
  • genetically modified trees
  • genetically modified salmon