Endangered Food Chain

Science

Students will learn about the far-reaching effects of environmental hazards, such as DDT and other chemical pesticides, through role-playing.

Background

The story of the peregrine falcon provides a clear example of the far-reaching impact of environmental hazards and the need for environmental protection laws. The falcon, the world's fastest bird of prey, has few natural enemies and thrives in many locations. In the 1960s, however, its population mysteriously decreased.

Through careful observation, scientists determined that falcon chicks were not hatching properly. Toxic residue from DDT and other chemical pesticides had resulted in a thinning of the eggshells. But these chemicals were not ingested directly by the falcons. They were used on grains that were eaten by smaller birds, which were, in turn, eaten by the falcons. Legislative action halted the use of toxic pesticides, and now the peregrine population is increasing.

What You Need

What to Do

  1. Have each student select a slip of paper with a role on it. Explain that in this activity, the grasshoppers hop, the starlings “fly” with short walking steps, and the larger birds “fly” with running steps. Have the students stand with their groups in a large circle.
  2. You will be a corn farmer in the Midwest. Plant your “corn” (some of the candy) in the middle of the circle. Tell the grasshoppers that they have one minute to “eat” (collect) as much corn as possible. Then ask the following questions:
    • What happened to the corn, and what does this mean to the farmer?
    • Who else depends on the corn crop?
    • What is the economic impact of grasshoppers ruining a crop?

    Brainstorm possible solutions for preventing the grasshoppers from damaging the crop again. What would be the cheapest solution? the most effective? the most environmentally sound?

    Plant the corn again. This time, finish the planting by spraying with the pesticide (colored water). Let the grasshoppers eat for one minute.

  3. Send out the starlings. Tell them that they have one minute to eat (tag) as many grasshoppers as they can. When a grasshopper is tagged, it must return to the outside of the circle and turn over its candy to the starling.
  4. At the end of the minute, tell any remaining grasshoppers that they are dead from the pesticide-treated corn. Now release the peregrine falcons to eat (tag) the starlings for one minute. Again, if a starling is tagged, it must return to the circle and surrender the candy.
  5. Finally, allow one minute for the owl and the eagle to hunt the falcons. At the end of the minute, ask the class why so many falcons remained. Discuss the scarcity of natural enemies and how that might impact the falcon population.
  6. Then tell the class that in the 1960s, the peregrine falcon was on its way to extinction. Based on the class activity, ask students in each group to hypothesize what might have happened. Share responses. Then tell the class the full story. Discuss how scientists and legislators worked together to remedy the situation. Ask how the farmers might have felt about the situation.
  7. Share the candy!

Teaching Options