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How Do Wetlands Filter Harmful Substances?

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Michigan Environmental Education Curriculum
Wetland Ecosystems

Harmful substances are often introduced into water bodies like streams, rivers, ponds, and lakes. Factories may dump toxic chemicals, or rainwater may carry harmful pesticides or animal waste from farms. Such harmful substances can have negative impacts on the wildlife that live in these water bodies. These substances may also enter the groundwater, which is where people get their water to drink!

So how do wetlands help? Wetlands reduce the amount of these harmful substances that enter a stream, river, pond, or lake by acting like a strainer that filters out the bad stuff. When these substances enter a wetland, before reaching the water body, wetland plants will take many of the harmful substances into their roots and change the harmful substances into less harmful ones before they are released to the water body. Harmful substances may also be buried in wetland soil, where bacteria and other microorganisms break the substances down so they are no longer harmful.

So, let's say there are two farms, each one is next to a lake. On one of the farms, there is a wetland next to the lake. On the other farm, there is not. Which farm do you think is going to release more harmful substances into the lake - the one with the wetland, or the one without the wetland? See the animation to find out.

REMEMBER!! Wetlands can only handle so many harmful substances and they can only make certain substances less harmful. It is therefore important to remember that even though wetlands filter harmful substances very well, we still must be careful and allow very little of these substances to enter a wetland or any other ecosystem.

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