Invasive species are organisms that spread into a new area and cause harm to native species, ecosystems, economies, or human health. They matter because ecosystems are built from many interactions, such as feeding, pollination, competition, and habitat use. When a fast spreading newcomer enters, it can change these interactions faster than native species can adapt.
The result can be lower biodiversity, damaged habitats, and disrupted ecosystem services such as clean water and crop pollination.
Many invasive species succeed because they reproduce quickly, tolerate many conditions, or arrive without the predators, parasites, and diseases that limited them in their original range. They may outcompete native species for light, food, space, nesting sites, or nutrients. Some alter food webs by becoming new predators, removing key plants, or changing nutrient cycles and fire patterns.
Management often combines prevention, early detection, physical removal, biological control, and long-term monitoring.
Key Facts
- An invasive species is nonnative to an ecosystem and causes ecological, economic, or health harm.
- Population growth can be modeled by N = N0(1 + r)^t, where N0 is the starting population, r is the growth rate per time step, and t is time.
- Competition occurs when species use the same limited resource, such as food, light, water, shelter, or nesting space.
- Biodiversity can be estimated by species richness, which is the number of different species in an area.
- A common spread rate formula is speed = distance / time.
- Effective management often follows prevention, early detection, rapid response, control, restoration, and monitoring.
Vocabulary
- Invasive species
- A nonnative species that spreads in a new area and causes harm to native species, ecosystems, economies, or human health.
- Native species
- A species that occurs naturally in a region and is part of its long-term ecological community.
- Biodiversity
- The variety of living organisms in an area, including species diversity, genetic diversity, and ecosystem diversity.
- Food web
- A network of feeding relationships that shows how energy and matter move through an ecosystem.
- Biological control
- The use of a natural enemy, such as a predator, parasite, or pathogen, to reduce the population of a pest or invasive species.
Common Mistakes to Avoid
- Calling every nonnative species invasive is wrong because some introduced species survive without spreading or causing measurable harm.
- Ignoring the early growth phase is wrong because small invasive populations are usually easier and cheaper to remove before they spread widely.
- Assuming one control method will solve the problem is wrong because invasive species often require combined strategies and repeated monitoring.
- Removing an invasive species without restoring natives is wrong because empty habitat and disturbed soil can allow the invader or another harmful species to return.
Practice Questions
- 1 An invasive plant population starts with 80 individuals and increases by 25% each year. Using N = N0(1 + r)^t, estimate the population after 3 years.
- 2 A zebra mussel infestation spreads 48 km along a river in 6 months. What is its average spread rate in km per month?
- 3 A lake has native snails, aquatic plants, fish, and birds. A new predatory fish is introduced and begins eating many native snails. Explain two ways this could change the food web and biodiversity of the lake.