WHAT IS A WETLAND? 



All of us are familiar with marshes and swamps either 

 through our own observations or readings. The term 

 "wetland." however, may be relatively new to many peo- 

 ple. Essentially, wetlands include the wide variety of 

 marshes, swamps and bogs that occur throughout the 

 country. They range from red maple swamps and black 

 spruce bogs in the northern states to salt marshes along 

 the coasts to bottomland hardwood forests in the southern 

 states to prairie potholes in the Midwest to playa lakes and 

 cottonwood-willow riparian wetlands in the western 

 states to the wet tundra of Alaska. 



Wetlands usually lie in depressions or along rivers, 

 lakes, and coastal waters where they are subject to period- 

 ic flooding. Some, however, occur on slopes where they 

 are associated with groundwater seeps. Conceptually, 

 wetlands lie between well-drained upland and permanent- 

 ly flooded deep waters of lakes, rivers and coastal embay- 

 ments (Figure 1). Recognizing this, one must determine 

 where along this natural wetness continuum wetland ends 

 and upland begins. Many wetlands form in distinct de- 

 pressions or basins that can be readily observed. Howev- 

 er, the wetland-upland boundary is not always that easy to 

 identify. Wetlands may occur in almost imperceptibly 

 shallow depressions and cover vast acreages. In the Prai- 

 rie Pothole Region, wetland boundaries change over time 



due to varying rainfall patterns. In these situations, only a 

 skilled wetland ecologist or other specialist can identify 

 the wetland boundary with precision. 



Wetlands were historically defined by scientists work- 

 ing in specialized fields, such as botany or hydrology. A 

 botanical definition would focus on the plants adapted to 

 flooding and/or saturated soil conditions, while a hy- 

 drologist's definition would emphasize the position of the 

 water table relative to the ground surface over time. A 

 more complete definition of wetland involves a multi- 

 disciplinary approach. The Service has taken this ap- 

 proach in developing its wetland definition and classifica- 

 tion system. 



The Fish and Wildhfe Service's 

 Definition of Wetlands 



Prior to conducting an inventory of the Nation's wet- 

 lands, the Service had to first define what a wetland is and 

 where along the soil moisture gradient to draw the line 

 between wetland and upland. To do this, the Service 

 enlisted the help of the Nation's leading wetland scien- 

 tists and selected four of them to develop a new wetlands 

 classification system (Figure 2). The authors represented 

 several disciplines including waterfowl biology, hydrol- 

 ogy, wetland ecology and marine biology. 



UPLAND 



UPLAND 



...^fiifS-. 



Water table 



V 

 Depressional Wetland 



— V — V — V — 



Overflow Deepwater Overflow 

 Wetland Habitat Wetland 



Water table 



Stream Groundwater 

 Discharge 



Seepage Wetland on Slope 



Fig. 1. Schematic diagram showing wetlands, deepwater habitats, and uplands on landscape. Note differences in wetlands due to hydrology 

 and topographic location. 



