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What's a Wetland?
IntroductionA wetland is pretty much what is sounds like--"wet land." It's a place where water meets land. There are wetlands on the coasts and along the Gulf of Mexico, called coastal wetlands. Here, in the Midwest, some wetlands have open water and cattails, rushes, or other plants like you'd probably imagine. But, some look like prairies, until you step in and water squishes out of the ground and gets your feet wet. Some occur along rivers and streams, and others are miles from the nearest river, stream or lake. Wetlands come in an amazing variety of shapes, sizes, and functions, but they all have three common characteristics:
WaterWater is the first ingredient of a wetland, but water doesn't have to be present year round. Some wetlands are wet in the spring and fall and dry during the hot summer months. These are known as seasonal or temporary wetlands. Just because they're only wet part of the year doesn't make them less important though. For example, these wetlands provide important "rest stops" for migrating ducks and geese as they return to their northern nesting grounds in the spring because these wetlands can be full of seeds and insect larvae at that time of year--a protein-packed snack for hungry puddle paddlers! Wetlands that are wet most to all of the year are called semi-permanent or permanent wetlands. In the spring wetlands and their surrounding vegetation can also be rest stops for migrating ducks and geese, as well as nesting areas. Permanent wetlands, like seasonal and semi-permanent wetlands, are also home to amphibians, insects, birds, crustaceans, mammals and many kinds of plants. Although wetlands, constitute only about 5 percent of the nation's lands, from 35 to 46 percent of all endangered and threatedned species are either dependent on or associated with wetlands areas. Over 100 of Iowa's animal and plant species recognized as being endangered, threatened, or of special concern are associated with wetlands and riparian areas. Sometimes wetlands have been drained for farming or other uses. This is usually done with underground tiles which are used to drain water from the land's surface. A drained wetland with crops planted on it is called a cropped wetland. The tile is like a bathtub drain and helps keep the land from being flooded, so the farmer can grow crops on it. If you plugged the drain, then the wetland would have water again. This is often the first step in restoring a wetland. (You can read about some Cool Kids who helped restore a wetland.)
SoilThe second criteria a wetland must meet is having wetland soil, but soil's soil. "What's the difference between wetland soil and the soil in the garden?" you may ask. There can be a lot of differences between soils. You've noticed that sand is different from clay and the compost in the backyard compost heap. Those are all components of soil. A soil is bits of rock, dust and decaying plant matter. Having more or less of one or more of these, makes one soil different from the rest. What's on top of the soil also affects the soil underneath. Soils that have prairies on top of them have different characteristics than soils that have woodlands on top of them. Wetland soils also have characteristics that make them different from other soils. Wetland soils are called hydric soils. Using a variety of tests, you can determine what kind of soil is present. The presence of a hydric soil is sometimes the first clue that a wetland was present at one time if none of the other characteristics (water or wetland plants) are at that location.
PlantsWater-loving plants are the third characteristic of a wetland. Wetland plants are specially adapted to the flooded or saturated conditions typically found in wetlands. Some plants are even adapted to the soil and water of one type of wetland. That's why many wetland plant species are considered rare, threatened, or endangered. They're very specific about their habitats, and those habitats have been disappearing for 150 years.
Types of wetlandsThere are many types of wetlands. Some are classified by from where the water comes. Water can come from two places. The first is surface water from precipitation (rain or snowfall). Many seasonal and semi-permanent wetlands, and some permanent wetlands, fill with rain or melted snow. The other souce of water is groundwater. Groundwater-fed wetlands are usually permanent wetlands. Sometimes it is hard to tell where a wetland gets its water. In one spot it can be fed by rainfall; another part of the same wetland it can be fed by groundwater. In Iowa we have palustrine, lacustrine and riverine wetland types. Prairie potholes are numerous throughout north central Iowa and the Upper Midwest and are called palustrine wetlands. They are shallow depressions that were created by a glacier several thousand years ago and filled with melted snow and rain. These seasonal and permanent wetlands made this region famous as the "thousand lake land" and the "prairie pothole region." Another type of wetland is called lacustrine. These are shallow lakes. Wetlands along rivers are called riverine wetlands. In Iowa, wetlands filled with groundwater are called seepage wetlands. Fens and bogs are seepage wetlands. Bogs have lots of dead plant material in their soil. Fens don't have as much dead plant material in their soil, and their water is different from bogs.
FunctionsAll these kinds of wetlands perform functions. Some functions include providing habitat for birds, animals and plants, and cleaning water of nutrients and pollutants. Wetlands can even help reduce flooding of streams and rivers. These functions make wetlands important and valuable to humans. But we don't know all the things wetlands do for us. That's why it's important to study, conserve, and restore wetlands. (Want to read more about kids learning and studying wetlands?) If you'd like to learn more about
wetlands and their functions, then check out the
Links
page. Also, check out the library
for some great books! |
