The Value and Function of Natural and Constructed Wetlands

by Curt Kerns, M.S., R.P.Bio., C.F.S.

North America once had vast areas of wetlands associated with virtually all rivers. Over their extensive range, beavers built ponds which quickly evolved into wetlands.  Since European agriculturists landed, over half of the wetlands of North America have been lost.  Extensive draining and diking has turned wetlands into croplands.  As towns grew into cities, wetlands were/are routinely filled for space. Many highways have been built through marshes if they happen to fall in the path.  While the present mammalian biomass of North America is on the same order as it was historically, distribution has changed.  Formerly much of the animal biomass was found in the vast grasslands of the Great Plains and the Prairies.  Runoff was filtered by sod, woodlands, and wetlands.  Particulate and dissolved nutrients were retained on land or were mineralized.  Currently most mammalian biomass is located near the coasts and Great Lakes.  Wastewaters are no longer filtered though natural systems instead pass partially treated into surface waters.  As the ecology of coastal waters did not evolve receiving complexed nutrients, significant changes have occurred.  Formerly harmful algae blooms were restricted to northern latitudes, probably stimulated by the carcasses of the billions of anadromous fish that historically graced rivers and streams.   Now complexed nutrients unfiltered by sod, forest and wetland are released in our storm, urban, and agricultural wastewaters.  Complexed nutrients stimulate marine bacteria, which allow dinoflagellates to bloom.  Dinoflagellates produce a variety of toxins, one being paralytic shellfish poison.

The majority of pelagic fish have lifecycle reliance on estuarine and coastal waters.  In the past 50 years, numbers of larger open ocean fish have plummeted, perhaps as much as by 90%.  Contaminated waters coupled with habitat loss, and unrelenting fishery pressures all contribute.  By restoring wetlands, by insuring that contaminants remain on land, and by more effective fisheries management, fish populations may rebound.  Constructing wetlands for contaminant removal is a well understood process.  This paper will discuss examples and opportunities for constructed wetland restoration.



“The significant problems we face cannot be solved at the same level of thinking we were at when we created them.” Albert Einstein

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