Ecological services derived from healthy streams, wetlands, and riparian zones include food, freshwater, flood control, water treatment, and recreational opportunities to mention only a few. They are vital for human well-being and maintaining healthy wildlife populations. Their benefits are felt locally in the form of providing drinking water and food, while on a global scale sequestering carbon and helping to regulate climate. The economic impacts are great. Some estimates put the world economic impact from ecological services at $18 trillion per year (Costanza et. al. 1997).

For a more in-depth discussion of all the ecological services wetlands provide: http://www.maweb.org/documents/document.358.aspx.pdf