Modify the lesson by launching the Cool-down with a discussion of beavers’ effects on the environment. Explain that beavers are sometimes regarded as pests that harm the environment by cutting down trees and building dams that cause flooding and block irrigation. Ask students to consider ways that beavers aid the environment. (They help store water, creating wetlands habitat for many species and protecting against drought. The water in a beaver pond is filtered as it seeps into the ground, preventing pollutants and excess nutrients from traveling downstream.)