Invasion! (WSJCANC)


This lesson will introduce ecosystem threats posed by non-native or invasive species of plants and animals. Participants will see that humans are usually the culprits for exotic species, which can quickly spread and overcome native species.

Grade Level:

4 - 12

Recommended Setting:

30 - 45 minutes

Outdoor Activity:



Witt Stephens Junior Central Arkansas Nature Center, Little Rock


Education Coordinator, 501-907-0636


30 - 45 minutes

Suggested Number of Participants:

10 - 30


  • Learn that invasive species of plants and animals are not native to Arkansas and can compete with native species for food, water, shelter and space.
  • Understand that invasive species are usually introduced and spread by people.
  • Realize that invasive species are often aggressive and may quickly crowd out native populations.
  • Identify examples of invasive species, explain the problems caused by them and ways to combat them.

Key Terms*:

Arkansas Game and Fish Commission (AGFC)

Amendment 75 of 1996

Bighead carp

Central Arkansas Nature Center (CANC)

Common carp


Endemic species

Eurasian collared dove


Introduced species

Invasive species


Northern snakehead

Silver carp


Water hyacinth

Zebra mussel

*See glossary for definations


AGFC news release on northern snakeheads

Common carp taxidermy mount

Fishing regulations guidebooks

Power Point presentation of invasive species in Arkansas

Zebra mussel display

Zebra mussels in North America flyer by the Ohio sea grant


The introduction of non-native (invasive) species by humans is a serious threat to the natural communities of plants and animals. Natural diseases or predators often are not brought with the invasive species. This can decrease a region’s native plant and animal diversity as these uncontrolled species increase and dominate native species.


  1. Introduce yourself and the CANC. Explain that it is owned and operated by AGFC and showcases the agency’s mission. Also tell how Amendment 75 of 1996 funds paid for the facility and allow free admission.
  2. Ask if they can define invasive or exotic species.
  3. Explain that people usually introduce exotic species into the environment. Ask the participants how this happens. List things such as introduction from ships and cargo (zebra mussels), release of plant and animal specimens by individuals (water hyacinth), escape of exotic pets or captured specimens (Eurasian collared dove, silver carp, black carp, bighead carp) and even intentional introduction gone awry (kudzu, common carp). Show the common carp taxidermy mount and explain that immigrants brought the species in the 1800s, and it is now prevalent in the United States. Use the Power Point presentation to survey the invasive species in Arkansas.
  4. Tell participants that introduced species often do not have natural predators, and their numbers can rapidly increase. Use the zebra mussel as an example. It is native to Russia and became established in the Great Lakes from ship ballast in the mid-1980s. It has spread to several other regions where it can quickly displace native mussel species and affect ecosystems. Zebra mussels filter large amounts of water and remove plankton. Each adult zebra mussel can filter one liter or more of water per day. Ask how this could affect the ecosystem. Some of the ways include reducing plankton levels for other species and thereby disrupting the food chain, clearing the water by filter feeding and allowing more sunlight to penetrate, and changing water flow levels by clogging water pipes and structures. All of these things can disrupt the ecosystem.
  5. Show the zebra mussel specimens. Point out that even though relatively small, zebra mussels collectively damage ecosystems through large populations. Studies from Lake Erie report up to 100,000 zebra mussels per square meter in some cases. Explain that once established, zebra mussels cannot be removed. However, people can take precautions to avoid spreading zebra mussels to unaffected lakes and rivers. Ask what things people could do to avoid spreading zebra mussels. Lead them through a discussion of the guidelines in the Zebra mussels in North America flyer by the Ohio sea grant.
  6. Ask why invasive species are a great concern to AGFC biologists. List reasons including harmful competition with native species, ecosystem damage, threats to the food chain, overproduction from lack of natural predators. Use the AGFC news release on northern snakehead fish (April 28, 2008) to illustrate how biologists must take action on invasive species. Ask for potential negative effects if the snakehead begins to spread across Arkansas and how citizens can help AGFC biologists address the problem. Point out how much money AGFC had to divert from other operations to address the snakehead issue. Use the fishing regulations guidebooks to explain that AGFC prohibits releasing non-native species in Arkansas, and note the violation fines.
  7. Ask the difference between invasive species and introduced species. Whereas invasive species are not welcome, introduced species are usually brought in by an authoritative body such as a governmental agency to correct a problem. Use the four trout species in Arkansas as an example. When the Corps of Engineers built large reservoirs in the mid-20th century for flood control, hydropower and drinking water, it changed the river environments. Cold water releases from the dams moved native species out of the tailwater sections of the rivers. Because many of the native species were popular sport fish, the government agreed to build trout hatcheries and stock trout to mitigate the loss. Trout thrive in cold water but cannot live in warm water. Therefore, they cannot spread beyond the tailwater sections of these rivers. Trout fishing created an economic boon in these areas, so this is a case of a carefully managed introduced species that has been extremely successful. Mention that Arkansas boasts world-class trout fisheries in the White and Little Red Rivers, and the current world record brown trout (40 pounds, 4 ounces) was caught from the Little Red River in 1992.



  • Why are invasive species serious threats to ecosystems? (They often have no natural predators, allowing them to dominate native species for food, water, shelter and space.)
  • What can invasive species do to native populations? (They can reduce the numbers of endemic species to the point of extirpation.)
  • How can we fight the spread of invasive species? (raise awareness of the problem, legislation to ban possession of certain exotics or release into the environment)

Participant Information Sheets:

Northern snakehead makes Arkansas arrival


Arkansas Game and Fish Commission (AGFC) – the state agency responsible for managing fish and wildlife populations

Bighead carp – exotic species from China that was stocked in some sewage lagoons to consume excess nutrients and algae in the 1970s; has since spread into some natural waters in Arkansas

Common carp – exotic species from China introduced to the US by immigrants in 1876 and to Arkansas by the 1880s, and is now widespread in the state; considered a nuisance fish because it causes turbidity and siltation by its bottom feeding habits

Ecosystem – the environment for a specific area and the organisms living within it that function as an ecological unit

Endemic species – animals native to a particular region

Eurasian collared dove – an exotic bird from India introduced to the US as a pet; escaped from cages into the wild and inhabits similar environments as mourning doves

Exotic – a species that has been introduced from another geographic region to an area outside its natural range

Introduced species – animals intentionally brought into an ecosystem by an agency responsible for management; four species of trout have been introduced to Arkansas by the US Fish & Wildlife Service to mitigate loss of native species below reservoir dams

Invasive species – non-native organisms which have been released into a region and have potential to disrupt ecosystems and displace native species

Kudzu – a fast growing Asian vine that was brought to the US to control erosion but has overtaken entire regions and displaced native plants

Northern snakehead – an exotic fish from China imported as an Asian food that was first discovered in US waters in 2002; discovered in Arkansas in 2008 as a result of escape from a fish farm; inhabits stagnant water and preys on native fish; AGFC banned possession of snakeheads in 2002

Silver carp – exotic species from China that was stocked in some sewage lagoons to consume excess nutrients and algae in the 1970s; has since spread into some natural waters in Arkansas; characteristically jumps from the water when disturbed by boat motor vibrations and can injure boaters by striking them

Trout – coldwater sport fish introduced by the US Fish & Wildlife Service to mitigate loss of native species in tailwaters below reservoir dams; four species are found in Arkansas: rainbow, brown, cutthroat, and brook

Water hyacinth – exotic, floating aquatic plant from South America that appeared in the US waters in the 1880s after being imported as an ornamental plant; threatens ecosystems by overcrowding native species, blocking sunlight beneath the water and clogging water intake pipes

Zebra mussel – a small exotic mussel from Russia that escaped into the Great Lakes in the mid 1980s from ship ballast water and has spread throughout major river drainages; impacts ecosystems by filtering water and changing the clarity, competing with native mussels, and clogging water intake pipes