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MNWR Photo |
Wetlands, the Vital Link |
Wetlands are very important to the well-being of many plants and animals, including people. But what are these areas, and what do they do?
A Wetland is the area between dry land and open water. It is sometimes covered with a shallow layer of water, but there are also wetlands which can be dry for part of the year. The plants and animals which live there are adapted to this watery environment. There are many different types of wetlands.
How do scientists determine what is a wetland and what is not?
Scientists delineate (draw the boundaries of) wetlands by looking closely at the plants, soils, and "wetness" in an area. Generally, when wetlands plants (certain species used as wetlands indicators) wetland soils, and a certain degree of wetness (hydrology) prevail, the area is called a wetland; when these things do not prevail, the area is called an upland.
Water
MNWR photo | First of all, in order to have a wetland there must be water. Makes sense, right? However, there may be areas that look completely dry that are still wetlands. A wetland is any area that is inundated (flooded) or saturated for a certain number of days in a row that add up to 7.5% of the growing season in an area. The growing season begins when the first buds on plants appear and ends with the first frost. For the rest of the year the area could have no water at all. Also, the water in a wetland may range from being salty, like along seashores, to being fresh, like in the freshwater marshes along streams and ponds. |
Wetland Plants
Photo: Ralph Tiner | Since there is a lot of water in the soil and very little oxygen, the plants that grow in wetlands are special plants. We call these plants hydrophytic plants. This means that they have special adaptations that allow them to grow in this unique environment. To succeed in their waterlogged environment, wetland plants must employ other strategies such as long, oxygen-transporting tubes (emergent reeds) or the ability to float on shallow water (lilies). |
Wetland Soil
Photo: Ralph Tiner |
Wetland (hydric) soils are saturated long enough in the growing season to create an anaerobic
(low oxygen) state in the soil horizon (the layers of soil found as you dig a hole) The
wetlands soil becomes so saturated with water that it cannot hold much, if any, oxygen. The
prolonged presence of water, and the resultant lack of oxygen, causes chemical changes that
eventually affect the color of the soil. By observing color characteristics of a soil sample, soil
scientists can determine if it is a hydric soil and how long or how frequently an area has been
wet.
Wetland soil layers may be either organic or mineral. Organic soils are characterized by a deep layer of decaying plant matter at the soil surface. This layer of organic matter keeps getting thicker because dead plant matter accumulates faster than it can decompose under anoxic conditions. Mineral soils are made of sand, silt, clay, and elements such as iron and manganese. Soil forms in layers called horizons. |
Animals
USFWS MNWR photo: Jessica Morgan | What about animals? Aren't animals important to a wetland? Of course they are! Although scientists don't use animals to determine which areas are wetlands, they are an important part of the wetland ecosystem. If you look for animals in a wetland, you may find all kinds of creatures, from the gigantic moose to the little dragonfly nymph. There will also be hundreds of animals you can't see that are either very small or living in the mud. |
Wetland Types Bog, swamp, salt marsh, pond: you've heard of all of these before and probably have an idea of what they look like. What you may not know is that they are all classified as wetlands, along with mangrove forests, riparian forests, vernal pools, and most other places where there is lots of water. Do you know the difference between all of these types of wetlands? Here's a helpful list of the different types of wetlands and how they are defined. Click on the link for a picture and description.
The lower 48 States once contained over 200 million acres of wetlands. For many years (all the way up until the early 1900's) they were looked at as "wastelands" because they were thought to have little use to people. Back in those days, people could not build on or farm them and some they couldn't travel through. So people began to find ways to use wetlands which often included draining off the water. They were used as dumps, ditched for mosquito control, dredged for canals, converted for agricultural use, and developed for industrial and residential uses. Today, we have lost half of our wetland habitats. An estimated 400,000 to 500,000 acres of wetlands are lost each year. New York State alone has lost 60 % (percent) of its original wetlands. People have started to recognize the value of wetlands and are now trying to protect them. Wetlands are not only are important for wildlife but also for people. They control floods, erosion, and sedimentation, improve water quality, recharge the water supply, and provide recreational opportunities.
An estimated 5,000 plants, 190 amphibians and reptiles, 1/3 of all birds, and 35% of all the federally listed threatened and endangered species depend on wetlands for their survival. The black tern is listed as an endangered (in danger of becoming extinct) species in New York State. It uses floating mats of cattail to build their nests on. If wetlands continue to be destroyed this species will not have a place to nest and may eventually become extinct (gone forever).
During times of heavy rainfall not all the water is absorbed into the soil and plants. Water runs off buildings, parking lots, and roads which cannot absorb water and heads toward lakes, rivers and streams. The level of water in these areas begin to rise increasing the water flow. These bodies of water can only hold a certain amount of water. The excess water overflows the banks creating floods in many areas including cities. Wetlands with their hydric soil act like a sponge by soaking up and storing the excess water. As the level of water in the lakes, rivers and streams begin to decrease the wetland will release the water at a rate they can handle. Thus, wetlands act as a flood control.
When it rains, the water runs off the land from the hilltops down into the valleys or lower areas and eventually ends in a stream, lake or river. As the water runs off it brings exposed soil sediment (or particles) down towards those bodies of water. If there is no wetland all the sediment will run into the water making the water depth more and more shallow. The sediment also destroys the spawning grounds for fish and may make them suffocate. If a wetland is present the sediment hits the plants and the low depression and slows down the water allowing the sediment to settle in the wetland. This helps prevent the sedimentation (or mud-clogging) of streams, lakes or rivers from erosion.
Runoff entering wetlands contains much more than just sediments. Pesticides, excess nutrients from fertilizers, bacteria, salts from winter road maintenance, and other chemicals also wash from the land and can enter our water ways. Scientists have found that after this polluted water has flowed through a wetland it becomes much cleaner. Wetlands, with all those plants and unique anaerobic (without oxygen) environment can protect lakes and streams from these substances by using the extra nutrients for their plants, and storing and breaking down the chemicals. This filtrating process improves the quality of the water for wildlife and humans.
Ground water is the source of drinking in many communities. Water stored in wetlands can recharge the ground water during dry periods. The water percolates (drain slowly) through the soils down to the water table where it can be used by people with wells.
Wetlands provide many pleasurable opportunities for people. Fishing, hunting, wildlife observation, photography, and canoeing are just a few examples.