Introduction
Once plentiful in the United States, wetlands are in serious decline now because of their loss to agriculture and commercial development. The United States has lost more than half of its original wetland areas. Even though development in wetlands is now regulated by the federal government, more than 300,000 acres are lost annually. But because people are realizing the important and valuable functions of wetlands, recent efforts have focused on restoring some of these lost resources. But wetland restoration is a complex and lengthy process. Ecologists are just beginning to learn about the effectiveness of various restoration strategies.
Wetland Functions
Wetlands have numerous functions. Among them are:
1. Flood control: Wetlands, often called natural sponges, help control flood waters by absorbing water during heavy rainfall, then slowly releasing it downstream.
2. Water quality and availability: Wetlands help purify water by processing nutrients, suspended materials and other pollutants. Wetlands also increase the availability of water by absorbing and storing water in wet seasons, then gradually releasing it during dry periods.
3. Erosion control: Because they are often located between water bodies and high ground, wetlands buffer shorelands against erosion. Wetland plants also bind soil with their roots and help to absorb the impact from wave action.
4. Fish and wildlife habitat: Most fish and shellfish eaten by humans live in wetlands when they are young. Wildlife also migrate through wetlands, and many endangered species, such as the wood stork, live there, as do many other birds, amphibians, reptiles and mammals.
5. Recreation: Wetlands attract hunters, fishermen, hikers and boaters. Wetlands are also havens for bird watchers and provide scenic inspiration for artists and writers.
Swamp Forest Restoration
Experiments with various flood-tolerant tree species and various planting methods have allowed Savannah River Ecology Laboratory researchers to accelerate by decades the recovery of a portion of the delta of Four Mile Creek, which was damaged by 30 years of nuclear reactor discharges at the U.S. Department of Energy's Savannah River Site near Aiken, S.C. Hot water destroyed 227 acres of the swamp forest. The delta no longer receives these discharges because the reactor was shut down in 1985.
In 1991, a DOE-funded mitigation program began funding research by the Ecology Laboratory, which conducted a dozen experiments with more than 4,500 trees of 24 different species. Researchers found that two flood-tolerant tree species, bald cypress and water tupelo, are suitable for all areas of the delta.
In sites that are not frequently flooded, additional species can survive: green ash, water hickory, overcup oak and nuttall oak. In the highest and less flooded areas, swamp chestnut oak, water oak and willow oak can become established. Researchers also found that the survival of the least expensive planting stock, bareroot saplings, was almost as high as the most expensive stock. And the use of plastic tube tree shelters prevent tree seedling destruction by beavers.
Carolina Bay Restoration
Many Carolina bay wetlands have been degraded or converted to non-wetland use. Restoration efforts have focused largely on restoring a bay's hydrology, or capability to hold water. But scientists at Savannah River Ecology Laboratory believe restoration is not successful until studies show that the replacement ecosystems are functioning at least equally as well.
So in 1994, they began a comprehensive study of the restoration of a 9-acre Carolina bay wetland on the U.S. Department of Energy's Savannah River Site near Aiken, S.C. The bay had been drained by a ditch for agricultural use sometime before 1951.
With scientists from the USDA Forest Service, researchers divided the bay into four sections and applied several experimental treatments. They were: logging only (mostly loblolly pine), burning only, logging and burning, and a control area with no treatment. Since the treatments were applied, researchers have been collecting and analyzing data related to the bay's vegetation, soil chemistry, water chemistry and aquatic invertebrates. The collective results from these four study areas will indicate the success of the restoration project.
In 1996, researchers found the wetland vegetation that once lived there had begun returning. The number of wetland and non- wetland plant species increased greatly -- compared to a pre- restoration study -- in the first year after workers closed a drainage ditch that emptied the bay, removed woody species and burned portions of the wetland. As the water level rose during the second growing season, the relative abundance of plant species shifted toward those that were more flood tolerant. An examination of the seed bank (seeds deposited in the soil underlying the bay) revealed that germinating wetland species were an important component of the initial vegetation response to the restoration efforts.
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