Slide 1
A non-native species is not automatically invasive
A non-native species occurs outside its natural range through human introduction. It is considered invasive when it causes or threatens harmful effects there.
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A species can be native in one region and introduced in another. The description requires a location and ecological context, rather than assigning an inherently invasive identity everywhere.
Slide 2
Introduced species can compete, prey or bring disease
An introduced species may compete with residents, eat them or bring disease. These mechanisms can alter populations and food webs.
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Several mechanisms may occur together, but each needs evidence. Finding a new species and observing a decline nearby does not by itself identify which interaction caused the change.
Slide 3
Some also change the habitat itself
Some invasive organisms alter physical conditions, nutrient cycling or fire patterns. Their effects extend beyond direct competition with one native species.
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A dense plant mat, for example, changes light and water conditions for other residents. Ecosystem effects can continue even when the introduced organism is not directly attacking those residents.
Slide 4
Finding a harmful introduction early creates options
Recognizing a harmful introduction while its range is small can make management more feasible. Monitoring is part of prevention as well as response.
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A useful record includes identity, location and evidence of establishment. Confusing a transient individual with a reproducing population can lead to a different assessment of the next steps.
Slide 5
Success means ecological recovery, not removal alone
Removing an invasive species is a means toward protecting ecological functions or residents. Success depends on what happens after removal too.
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Native recovery may be limited by other habitat changes or missing species. Tracking the desired community response prevents removal totals from being mistaken for complete ecosystem recovery.
Sources
- Learn: Invasive and Non-Native Species
National Park Service
- Nonindigenous Aquatic Species: impacts
US Geological Survey