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Environmental Science
Invasive Species and Ecosystem Impact
How non-native species disrupt habitats and food webs
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Invasive species are organisms that arrive in a new ecosystem, spread rapidly, and cause harm to native species, habitats, or human activities. They matter because ecosystems depend on balanced relationships among producers, consumers, decomposers, and physical conditions such as water and soil quality. When an invader has few predators or competitors, it can grow quickly and disrupt food webs. The result can be loss of biodiversity, reduced ecosystem services, and major economic costs.
Key Facts
- Population growth without strong limits can be modeled as N(t) = N0e^(rt), where r is the growth rate.
- A species is invasive when it is nonnative, spreads successfully, and causes ecological, economic, or health damage.
- Biodiversity can be estimated with species richness, which is the number of different species in an area.
- Percent change = ((new value - original value) / original value) x 100%.
- Invasive species often succeed because they have high reproduction, broad diets, fast dispersal, or few natural enemies.
- Prevention and early detection usually cost less and work better than trying to remove a widespread invader.
Vocabulary
- Invasive species
- A nonnative organism that spreads in a new area and causes harm to ecosystems, economies, or human health.
- Native species
- A species that naturally occurs in a region because it evolved there or arrived without human-caused introduction.
- Biodiversity
- The variety of living organisms in an ecosystem, including different species, genes, and habitats.
- Food web
- A network of feeding relationships that shows how energy and matter move through an ecosystem.
- Ecological niche
- The role a species plays in its ecosystem, including what it eats, where it lives, and how it interacts with other organisms.
Common Mistakes to Avoid
- Calling every nonnative species invasive is wrong because some introduced species do not spread or cause measurable harm.
- Assuming an invasive species only affects one native species is wrong because changes can cascade through predators, prey, competitors, soil, and water quality.
- Ignoring time in population estimates is wrong because fast reproduction can make a small introduction become a large outbreak after several generations.
- Using only the number of individual organisms to judge ecosystem health is wrong because a habitat can contain many individuals but very low species diversity.
Practice Questions
- 1 A lake has 200 native snails before an invasive snail arrives. Five years later, only 80 native snails remain. What is the percent change in the native snail population?
- 2 An invasive plant population starts with 50 individuals and doubles every year. How many individuals will there be after 4 years if no limiting factors slow its growth?
- 3 A wetland has an invasive plant that forms dense mats on the water surface. Explain two ways this could affect fish, insects, or birds in the food web.