To teach students about the interdependent nature of natural ecosystems, have the third grade class act out each link of an ecosystem's "web" of connections. Assign each student one species within a local ecosystem. For example, one student can play the role of a specific flowering plant; another student can portray the plant's natural pollinator insect; while a third student can play a small bird that habitually eats the insect. Have all the students stand in a circle, and hand a ball of yarn or a roll of string to the student at the bottom of the food chain. Read a step-by-step description of the ecosystem's various links, having the students toss the string along as you read. By the end, your students will have formed a highly intricate web within the circle. Finally, have a student who represents the human species tug suddenly on the string. Watch how the whole web becomes skewed or breaks as a result.
As part of the Earth Day Groceries Project, have your third grade students team up with local supermarkets and distribute their messages of environmental awareness to shoppers in the community. To participate, find a local grocery store willing to let your class borrow paper grocery bags. Have students draw inspirational and educational pictures and slogans on the bags, encouraging environmental awareness and responsibility. Return the bags to the grocery store, where they will be used, spreading your students' message across the community. If your third graders are a technologically savvy bunch, set up a website to go along with the project and write its web address on the bags, as well.
Have your students take an up-close look at how they impact nature at the most direct and personal level. For this activity, bring the whole class to a relatively undisturbed, natural area; if necessary, organize a field trip to a beach, a state park or a nearby nature preserve. Beforehand, instruct the students that they will be sitting in nature for an extended period without making any sound. When you arrive, have students sit for 20 to 30 minutes, quietly writing down everything they can hear and observe when they are quiet, such as wildlife activity or birdsong.
As a conclusion to your studies on the impact of humans on the environment, ask the students what they think would happen if they fell asleep and woke up 100 years in the future. Have students write creative essays, comparison and contrast or narratives, about what would happen to the environment over a 100-year period if human behavior remains the same, or changes.