What is an invasive species?




Invasive species are non-native plants, animals, or other organisms that did not historically occur in Maine. When introduced to Maine ecosystems, they develop abundant, widespread populations that negatively impact the environment, the economy, human health, or the way we live. Common reed, variable watermilfoil, and Chinese mitten crabs are examples of species that are invasive to Maine.



Maine’s native species are plants, animals, or other organisms that have historically occurred and evolved in Maine ecosystems. Milkweed, rock crabs, and little floating heart are examples of species that are native to Maine.


    Non-native species have been either intentionally or accidentally introduced to Maine by humans or their activities. Non-native species do not cause environmental or economic harm. An important, not-to-be-missed distinction between non-native species and invasive species is that non-native species do not disrupt the natural functions and processes of our native ecosystems. Check out Mission: Sea Potato and Mission: Hungry, Hungry, Beetles for two non-native species that students and scientists are investigating.

Why VS cares

Invasive species affect Maine's native species and natural ecosystem processes, impact our economy, and change our relationship with and reliance on our environment. Maine is a big place. Looking for invasive species along Maine's 32,000 miles of rivers and streams, 6,000 lakes and ponds, 5,000 miles of coastline, and millions of acres of forests, fields, and developed areas is a sizable challenge. But this statewide Vital Signs community is making it happen!

    Knowing where invasive species are FOUND helps scientists and resource managers target their own research efforts. Finding invasive species before they establish populations keeps Maine relatively free of invasive species.

    Knowing where a species has been looked for but NOT FOUND is just as important as knowing where it has been found. It offers critical insight into species ranges, seasonal or annual fluctuations, species movement, and habitat preferences.

    Knowing where natives species are establishes an important baseline of information from which we can see how a place changes with time when an invasive species moves in.

What VS is doing

The magnitude of student involvement promises to build a heightened level of public awareness and a meaningful body of scientific knowledge that is essential for biologists and resource managers committed to addressing invasive species issues.
David Littell, Maine Department of Environmental Protection

The VS community is documenting where native and invasive species are FOUND and NOT FOUND in ecosystems across Maine.

Together we're using our high-speed network of 32,000 middle school students, our forward-thinking teachers, our passionate citizen scientist community, and our committed invasive species scientists and natural resource managers. Everyone - novices and experts alike - are making meaningful contributions to this effort by publishing, reviewing, or using the native and invasive species observations in the Vital Signs database.

Join us by looking for species in your special corner of Maine!