Ask: Why are wetlands important? Students should be able to answer this question based on the previous day’s lesson and the reading. Introduce the term “function” to explain the different processes, or “jobs” organisms within ecosystems perform, such as water purification, climate regulation, fertilization, etc. When an ecosystem changes, its functions change too – for example, if you were to change a forest into an agricultural field, the amount of nutrients in the streams running through the area would change, because the trees that used to remove those nutrients are no longer there. A function that many students understand is feeding – producers, consumers, and decomposers are groups of organisms that perform the same function in an ecosystem.
Display several objects (or pictures of objects) that are common household items for which students should know the function – a vacuum cleaner, a stove, a lamp. Then, hold up a plant – ask students what functions a plant provides. Students may mention that plants produce oxygen, but they may also mention that plants produce food, habitat, or sequester carbon. Explain what a metaphor is and how it may be used in literature or in English. In science, metaphors are often used to explain or help visualize something. Introduce the metaphors activity by asking students what common item they might use to suggest the function of a plant – students might suggest food, a balloon filled with air, or a dog house to represent habitat. Hand out the Wetland Functions worksheet and have students keep track of the functions as they visit each station.
Have items placed around the room so that groups can rotate through each station. Each station must have a station number (see below). A timer will help keep students flowing and focused. Allow 1-2 minutes per station. Students will fill in the number of the station that they think matches the function and write down the metaphor items on the line to the right of the function. After the last station, go through each station and see if their numbers match. Did everyone have #1 for Habitat for many species?, etc. Go through each function and check.
#1: Home Sweet Home sign: habitat for many species
#2: Storage box/water bottle: Recharges groundwater by storing excess water
#3: Baby food and pacifier: Provides a nursery that shelters, protects, and feeds you wildlife
#4: Net: Reduces erosion by trapping sediment
#5: Coffee filter: Filters excess nutrients and toxins from the water
#6: Lunch box with apple: Provides a nutrient rich food supply
#7: Sponge: Reduces flooding by absorbing and storing excess water
Explain: Hand out the Metaphors Notes worksheet for students to take notes as you discuss their answers to the activity (or have students take notes on their own paper). Ask students to critique the metaphors – how is this activity a good model for what really happens in wetlands, and what could be improved. The lesson is designed to hit on subtle differences in the functions of a wetland.
- How is a net different from a coffee filter? The holes are different sizes; nutrients and pollutants need fine filtration system; and the net represents plant roots which trap sediment and thus reduce erosion in the mainstem of the river. However both deal with removing & trapping particles from the water.
- The lunch box with the apple and the baby food and pacifier are similar; however the baby food and pacifier should get them to link to the word “nursery.” What do they think about when they hear the word nursery? How would a wetland provide shelter, protection, and food for young wildlife? Wetlands are one of the most biologically productive places on earth. A wetland is filled with aquatic plants that grow in the shallow waters. These plants provide food, but also nesting grounds and shelter for many species which is why wetlands are so biodiverse. The lunch box and apple represent the fact that wetlands provide a nutrient-rich food supply. Plants are a good food source but wetlands are also home to many invertebrates and microscopic organisms that are food to larger species.
- The Home Sweet Home sign is more of a generalized function that is connected to the lunch box/apple, baby food/pacifier and the pillow/blanket.
- Students typically understand that a sponge stores water. Wetlands can reduce flooding by soaking up floodwaters. Water moves slowly through a wetland which slows down the momentum of water.
- The storage box/water bottle represents the idea that wetlands store water, allowing it to slowly infiltrate into the ground.
Ask students to brainstorm what other kinds of functions wetlands might perform, but which weren’t part of the activity. Examples include: produce dissolved oxygen, provide recreational spaces, decompose organic matter, remove nitrates.
Students should read “Constructed Treatment Wetlands.”
An interesting example of a constructed wetland (called a “Living Machine”) can be seen at the Omega Center for Sustainable Living (OCSL) in Rhinebeck, NY. Field trips are possible and very informative.
You could also show a youtube video on living machines if a field trip isn’t an option: http://www.youtube.com/watch?v=8_bxxUub9HU .
Ask students to explain, in writing, what functions constructed wetlands perform.
Exit slip question: What functions do wetlands perform?