What Makes A Wetland A Wetland?

There is no one definition that can describe all wetlands. This is because no two wetlands are exactly alike: they come in various shapes and sizes, with different hydrology, soil condition, and dominant vegetation. Wetlands occur in all fifty states and tend to be located in depressions or low-lying areas beside lakes, rivers, and streams and along coastlines. Wetlands usually contain calm, shallow waters and can be as small as a half acre pond in Iowa or as large as the broad shallow 5,000-square-mile wetland area that comprises the Florida Everglades- one of the world's largest marshes.

Despite all these differences wetlands do share some characteristics that set them apart from other kinds of habitats. Wetland habitats, at least periodically, have saturated or waterlogged soils and contain plant and animal communities particularly adapted to live in these soggy conditions.

What Makes A Wetland Wet?

The answer to this is as varied as the wetlands themselves. Most wetlands are located in low-lying areas and thus are inundated by rain and run-off. In places where the ground water table lies close to the surface the wetland is constantly fed water from below. Saltwater marshes along the coasts stay wet because of the diurnal flooding of the tides. Some wetlands that lie close to rivers, streams and lakes, are saturated when the bodies of water they lie next to, overflow their boundaries.

Wetlands Are Not Wastelands

In the past, wetland areas were thought of as swamps that were only useful to mosquitoes and pests. Wetlands were readily drained, filled, and replaced with something more "functional". Many prisons, airports and industrial complexes were built on filled in wetland areas. Recently we have come to understand that the wetland habitat can be of great value to humans economically as well as aesthetically.

The wetland habitat is a highly productive ecosystem. These soggy areas, when healthy, support more life than most other habitats, even tropical rain forests! It is this high productivity that makes our wetlands very useful to wildlife, and in turn useful to us humans. Many waterfowl use these areas as resting, breeding, and feeding places or as a pitstop during migrations. There is a good chance that if you visited our local wetland area during spring or fall, you would encounter many different types of migrating birds. Coastal wetland plants provide a prime location for the spawning of fish and a nursery ground for oysters, crabs, and shrimps. Many rare or endangered species make their homes in wetland communities. American crocodiles, whooping cranes, wood storks, and snail kites are all endangered, and all live in wetlands.

Many animals linked to the wetlands are economically important. Hunters spend considerable amounts of money each year to hunt waterfowl. Sea trout, flounder, and blue fish all spawn in the coastal wetlands. These fish, as well as shellfish like oysters, shrimp, and crab, are commercially valuable as food for we humans.

Wetlands, in their natural state, act as flood controllers. They help absorb floodwaters from nearby rivers and lakes. As the water overflows into the wetland it naturally loses velocity and the wetland vegetation slows the water even more. This helps protect surrounding farms and developed areas. By slowing down the water flow, wetlands allow suspended solids to slowly settle. Otherwise the suspended solids would be carried downstream where they could build up and congest rivers and clog the gills of aquatic animals.

Wetland vegetation does more to flood water than just slow it down, it also acts as a filter, collecting and recycling pollutants. Many communities are taking advantage of the ability of the wetland ecosystem to thrive on nutrient-rich water. Both natural and human- made wetlands are being employed in the last stages of wastewater treatment and storm water run-off. Wetland plants are ideal for wastewater treatment because they are able to survive in anaerobic soil conditions, (which is the product of nutrient rich water) and they convert potential pollutants, such as phosphorus and nitrogen, into biomass through assimilation.

Although many of our wetlands are now industrial complexes, farms or forests, people are starting to realize the value of wetlands just as they are. Not only are they commercially valuable, they provide storm protection for near-by farms and communities, they are a refuge for a variety of wildlife, and a peaceful haven for nature lovers. Lastly we should remember that every community, including the wetlands, has an inherent value that can't be measured by our constructed values.

Our Local Sweetwater Wetland

Here in Tucson, we are lucky to have a wetland area in our urban community­Sweetwater Wetlands. Sweetwater Wetlands is an artificial wetland area located on the east bank of the Santa Cruz River near Prince Road. It was built in 1996 under the direction of a committee with representatives from the US Fish and Wildlife Service, US Forest Service, Arizona Game and Fish Department, City Parks and Recreation Department, the University of Arizona and many local environmental education and wildlife organizations. This wetland area serves a dual function, it cleans-up wastewater while serving as a wildlife habitat and environmental education facility. It takes the secondary effluent from Pima County's Roger Road Treatment Plant and provides further natural water treatment. It also treats 1.6 million gallons of backwash water per day from the city's reclaimed water treatment plant. The treated water is then used to help irrigate Tucson's parks, schoolyards, golf courses, and median strips. This reuse of water is important in our efforts to conserve one of the desert's most precious resources­water.

Wetlands at Work

How does the wetland recycle our wastewater? In the first step the incoming water flows into settling basins. Here any suspended solids in the water will fall to the bottom of the basin. From the settling basins the water flows into the polishing ponds where it is further treated by microbial processes. These polishing ponds are filled with aquatic plants such as bulrush and cattail that provide an environment for microbes to live. The microbes use both aerobic and anaerobic processes to change high nitrogen concentrations into nutrients useful to the pond ecosystem. Finally, the naturally treated water flows into the recharge basins where it filters through soils and is stored for reuse in the city's reclaimed water system.

Wetland Ecology

Ecology is the study of the relationships of living things to each other and to their environments. It seeks to answer the "how" and "why" questions in relation to a particular area. Why do mosquitoes thrive in stagnant waters? Why do Bellastoma tend to dominate the pools of the Sweetwater wetlands? Why are our riparian areas vanishing? How does human activity affect our wetlands? How can we restore our riparian areas? These questions can be very difficult to definitively answer. But our speculations can help us understand more about the community in question, and hopefully, guide our actions so that the greatest positive results are achieved.

Who Lives At Sweetwater?

Sweetwater wetlands is a community of animals and plants with it's own unique character. The lifeforms are abundant as well as varied and different from that which we would typically find in our Sonoran Desert. Take a little time to visit Sweetwater, you will find it has much to contribute to a tranquil morning walk.

As you step out of your car the first thing you might notice is the lush green area in front of you. This artificial wetland area stands out in our Sonoran desert landscape, although the Santa Cruz River once supported a wetland area that stretched for hundreds of miles. As you walk toward the ponds you will find yourself among cottonwood, willow and other large-leaf shade trees. When you reach the pond you will notice the many dense sedge, rush, cattail and reed plants. Quietly sitting on the tips of these plants you will find dragonflies and damselflies awaiting the perfect opportunity to swoop down and catch a meal. The larvae of these insects live at the water's edge clinging to submerged vegetation. Young of the dragonfly move around on this vegetation stalking their prey. When an organism comes into range, the dragonfly larva will unfold a special appendage under its head; the appendage shoots out, pierces the prey, and then scoops it up and into its mouth.

Find a spot where you can see the water. As you peer down on the pond you will notice water striders skating and jumping about on the water surface. These creatures have waxy hairs on their legs. The arrangement of these hairs and their waxy coating repel water and this is what keeps these insects afloat.

If you adjust your eyes and look into the water you will notice much activity right below the surface. In this area you are likely to find water scorpions, mosquito larvae and pupae, water boatmen, and backswimmers. Water boatmen and backswimmers are often confused as the look and behave in a similar fashion. But if you look closely you will notice that they have different manners of swimming. The backswimmer prefers to lay on its back and propel itself forward with its powerful legs, whereas the water boatman glides around right side up. This area right below the surface is highly populated with many interesting insects. This is because aquatic insects are air breathers and must occasionally visit the water surface to replenish their air supplies. Many will hang from some sort of breathing tube that connects them to the water surface and in this way they are able to breathe air.

Further down, beyond where you can see into the water, in the bottom soils, live the larvae of predaceous diving beetles and midges. The adult midge resembles a small mosquito, but it does not bite. The larvae of midges are sometimes called "bloodworms" because of their characteristic blood-red color. This color is due to a red pigment that aids the organism in breathing at very low oxygen levels.

Now step back and take a moment to think about all of the creatures you have seen. Think about how each one has a unique approach to survival in the wetland. Each of the plants and animals etch out a corner of the wetland community where it fits best, but none could survive independent of the community. All living things maintain interactions with the other living things around it. One may depend on others as a source of food or to provide breeding ground. Some organisms will compete with others for resources. There are many different interactions and studying these relationships will give us a better understanding of the community as a whole.

The Wetland Web of Life

The plants and animals of the Sweetwater wetland area live together in what we call an ecological community. Within this community all living things interact. Some interactions involve food and feeding and some involve habitat space and protection. It is these relations that link each living thing to others within its community like links in a chain. However, the chain of life isn't this simple. In fact, each organism has links to many different organisms, which are linked to other organisms, and so on. So it is easier and more appropriate to picture a community as a complex spider's web where each interaction between two living things forms one strand of the web. Since every plant and animal can potentially interact with every other member of the community the many strands connect to form a beautifully complex and unique web of life.

The wetland community is an ensemble of plants and animals that are specially equipped to live in soggy conditions. Each living thing plays an important role. Plants, like duck weed, sedges and cattails, are the primary producers in this community. Through the action of chlorophyll plants are able to convert water, carbon dioxide and the suns energy into carbohydrates in the form of plant mass. This is the first step in the energy transfer through the wetland system. Animals, herbivores and omnivores such as ground squirrels and water scorpions, then eat the plants and the energy flows into them. These animals are known as primary consumers. Carnivores such as dragonflies and kestrels, the secondary consumers, eat the primary consumers and again the energy is transferred, and so on. When animals and plants die their organic materials are broken down by the actions of detritivores into nutrients that can be used again in the system. Plants will use these nutrients and the cycle is complete. Each predator and prey and every connection is very important for the movement of energy.

Many of the connections of a community involve feeding and the transfer of energy, but there are other types of relationships. Many plants are pollinated with the help of flying critters. Bees and birds pollinate as they fly from plant to plant. As they feed they inadvertently collect pollen on their body which may rub off them and on to the next flower they visit. In turn, plants provide a good breeding area for birds, fish and insects. Plants can also provide protection for animals, both protection from the abiotic influences of the community, such as harsh weather, and protection from predation.