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May 25, 2011

What's the Point of a Wetland?

Although large-scale benefits of functions can be valued, determining the value of individual wetlands is difficult because they differ widely and do not all perform the same functions or perform functions equally well. We all must understand that impacts on wetland functions can eliminate or diminish the values of wetlands.

Water storage:
Wetlands function like natural tubs or sponges, storing water and slowly releasing it.  This process slows the water's momentum and erosive potential, reduces flood heights, and allows for ground water recharge, which contributes to base flow to surface water systems during dry periods.  Although a small wetland might not store much water, a network of many small wetlands can store an enormous amount of water.  The ability of wetlands to store floodwaters reduces the risk of costly property damage and loss of life - benefits that have economic value to us. 

The flooding of the Mississippi River Basin in the spring of 2011 has caused billions of dollars in property damage, resulted in many deaths, and has devasted the lives of thousands.   Historically, over 20 million acres of wetlands in this area had been drained or filled for either commercial, residential, or agricultural purposes.  If the wetlands had been preserved rather than drained or filled, most of this damage could have been avoided. 

Water filtration:
After being slowed by a wetland, water moves around plants, allowing the suspended sediment to drop out and settle to the wetland floor.  Nutrients from fertilizer application, manure, leaking septic tanks, and municipal sewage that are dissolved in the water are often absorbed by plant roots and microorganisms in the soil.  Other pollutants stick to soil particles.  In many cases, this filtration process removes much of the water's nutrient and pollutant load by the time it leaves a wetland.  Some types of wetlands are so good at this filtration function that envrionmnetal managers construct similar artificial wetlands to treat storm water and wastewater. 

Biological productivity:
Wetlands are some of the most biologically productive natural ecosystems in the world, comparable to tropical rain forests and coral reefs in their productivity and the diversity of species they support.  Abundant vegetation and shallow water provide diverse habitats for fish and wildlife.  Aquatic plant life flourishes in the nutrient-rich environment, and energy converted by the plants is passed up the food chain to fish, waterfowl, and other wildlife and to us as well. 

Did you know?
  • An acre of wetland can store 1-1.5 million gallons of floodwater.
  • Up to one-half of North American bird species nest or feed in wetlands.
  • Although wetlands keep only about 5% of the total land surface in the conterminous United States, they are home to 31% of our plant species. 
These beneficial services, considered valuable to socities worldwide, are the result of the inherent and unique natural characteristics of wetlands. 

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