Wetlands are important for water filtration because they act as natural filters, trapping sediment, nutrients, and pollutants from the water as it flows through them. The plants and soil in wetlands help to absorb and break down harmful substances, improving water quality before it reaches rivers, lakes, and other water bodies. Wetlands also provide habitat for various microorganisms that further purify the water by breaking down organic matter and contaminants. Overall, wetlands play a crucial role in maintaining clean and healthy water systems.