Ways in which wetlands are misused

Privacy Copyright. Skip to main content. Home Institution Illinois Wesleyan University. Abstract This research examines the complex and inter related relationship between conservation and development of wetlands in Kampala.

Article Location. Search Enter search terms:. Water misuse, climate change threaten increased malnutrition and disease — UN. Irrigated agriculture accounts for 70 per cent of withdrawals with only 30 per cent returned to the environment - compared with industry and households which return up to 90 per cent.

Knowledge gaps, especially with regard to aquifers, are an increasingly significant hindrance for effective water management, with many developing countries operating in the dark on the size of water resource and precise patterns of supply and demand.

The intertidal cordgrass marsh created out of high marsh at the mitigation site appears to have met its goals of enhancing habitat heterogeneity, vegetational diversity, and wildlife utilization, principally by birds.

However, the project should be viewed as a habitat enhancement and conversion rather than an ecosystem restoration for the following reasons:. The mitigation did not endeavor to recreate the particular estuarine ecosystem that existed on the site prior to the damming of the Hackensack River and prior to other significant environmental modifications that have occurred in the Meadowlands.

Because of the limited areal scope of the mitigation work and limited goals, the mitigation project had virtually no impact on the regionwide ecological degradation of the Meadowlands. The resulting habitat cannot be considered ''restored," because of the influence of these intractable conditions on the mitigation project site. Where once there was probably a high marsh of Spartina patens, Distichlis spicata, and other species, the contractors produced an intertidal marsh with mud flats and raised islands of woody vegetation.

There is no evidence that the ecosystem created on the mitigation site has existed there within human memory. Water quality in the Hackensack River appears to be far better than the sewerlike conditions reported Certain aquatic organisms, such as grass shrimp and mummichog, are now thriving in vast numbers, and some species of waterfowl and fish have returned. However, as this committee has pointed out elsewhere, ecosystem restoration involves more than water quality improvement and increased wildlife use.

Within San Diego Bay and in San Diego County as a whole, only about 10 percent of the natural salt marsh acreage has escaped urban development. The Hackensack Meadowlands site is a second example of restoration efforts undertaken in an extremely disturbed urban setting see Box 6. In both these cases, the sites have experienced great damage both locally and to their biological support systems.

Systems with an intermediate degree of disturbance Figure 6. Several examples illustrate the variety of challenges facing restoration projects in such sites.

These isolated elliptical wetlands range in size from less than 50 m to more than 8 km in diameter and may be either only temporarily inundated or permanently flooded. Although they occupy a small areal portion of the landscape, their ecological importance to wetland and semiaquatic organisms is great Sharitz and Gibbons, Most of these wetlands have been disturbed, chiefly through ditching and draining to support agricultural usage. Many have been repeatedly plowed and planted or continually grazed by livestock; permanent ponds have been dug in others.

Most of these bays are surrounded by agricultural land or managed forests; very few are physically connected with other wetlands Sharitz and Gibbons, Reestablishing the hydroperiod by closing ditches or filling artificial ponds and cessation of agricultural use may allow these bays to resume their wetland function Schalles et al. On the Savannah River site in South Carolina, characteristic biotic communities have recovered in the 40 years since agricultural usage ceased and natural hydroperiod was reestablished.

The persistent seed bank allows rapid recovery of the vegetation of these wetlands if disturbance has not been excessively severe e. Dispersal of wetland plant species to recovering bays may be facilitated by waterfowl that use these wetlands when they are inundated. Thus, functional recovery of these systems may occur relatively rapidly after restoration of a more natural hydrologic state.

The Salmon River salt marsh in Oregon Frenkel and Morlan, is also an example of a site with intermediate restoration potential— the effects of disturbance are not easily reversible, yet the site exists within a region that has large reserves of natural habitat.

In this case, a ha salt marsh was diked in and used for grazing, as fresh water gradually diluted the salts and allowed pasture vegetation to become established. During the year diked period, the topography subsided 30 to 40 cm due to compaction and loss of soil buoyancy. Forest Service breached the dike in to restore the salt marsh to a functional ecosystem. However, the topographic subsidence was not readily reversible. Ten years after dike breaching, accretion had raised the topography only 2 to 5 cm throughout most of the site.

Native salt marsh plants have now reestablished themselves at their appropriate intertidal elevations, but the area of low salt marsh is much larger than that present before diking. From a functional standpoint, aboveground biomass indicates a high level of similarity with productivity in reference wetlands.

Thus, the restoration process is under way, but at the current rate of accretion, reestablishment of the predisturbance high salt marsh could take several decades.

The case is an example of a site that would fall in the upper left portion of the model shown in Figure 6. In the northern United States and Canada, prairie pothole wetlands were altered by European settlers to facilitate farming see case study, Appendix A. The poorly drained depression soils were drained by elaborate and extensive tile fields, seasonal inundation was eliminated, and the potholes were converted to tillable land.

Approximately one-half of the 20 million acres was drained, with dramatic effects on fish and wildlife habitat. Restoration efforts supported by federal, state, local, and private programs are now under way. Physical measures to restore the natural hydrology, such as breaking the tile fields and filling ditches, followed by natural recovery of wetland plant communities, have restored waterfowl habitat. The chief obstacle is development of a program to persuade individual landowners to take pothole areas out of agricultural production and allow.

Many of these pothole sites could be described as falling in the lower right portion of Figure 6. Bottomland hardwood forests of the southeastern United States have undergone rapid reductions in area and changes in composition Box 6.

The lower Mississippi River floodplain is an example of a large-scale disturbance in which the physical condition of the wetland area has been altered and cumulative impacts have occurred.

Large areas of mature forested wetlands have been removed or totally disrupted through diking, draining, and clearing for conversion to agriculture, and through urban encroachment. Extensive federal water management and flood control programs in the Mississippi watershed have altered the basin hydrology on a large scale and have allowed major changes in land use to occur.

Thus, within this landscape, only 23 percent of the area of floodplain forest remains Tiner, The converted agricultural lands typically retain the natural alluvial soils even though the hydrology of these floodplain and backwater areas has been substantially altered.

If crop cultivation ceased, wetland vegetation including forests would be reestablished eventually in much of the area because the poorly drained alluvial soils hold sufficient moisture. Blockage of small drainage ditches and canals and breaching of levees or dikes would enhance recovery of riverine overflow hydrologic conditions. These former forests could be characterized as falling somewhere in the middle of the model shown in Figure 6.

Reforestation with bottomland species is being undertaken in several large-scale efforts on federal lands, with wildlife habitat and increased timber values as the goal.

Much of the converted wetland area in the lower Mississippi valley is privately owned, however. Furthermore, removal of large water-control structures is not politically or economically realistic. Thus, the major constraints on wetland restoration in the lower Mississippi valley are not so much physical or technical as institutional and economic.

If the model shown in Figure 6. Understanding the factors that limit restoration potential can lead to setting realistic goals for systems that will be most difficult to restore and to making better decisions when restoration is proposed as mitigation for further destruction of wetland habitat.

Because some landscapes have lost the majority of their wetland area to irreversible uses, restoration opportunities may be few in these areas.

The remaining degraded systems may be highly stressed, yet. At the time of European settlement, approximately 80 million hectares of forested wetlands existed in the conterminous United States.

By the mids, this area had been reduced to about Drainage, logging, and conversion to agriculture accounted for most of the losses, especially in the Mississippi floodplain, where 78 percent of the forested wetlands have been lost MacDonald et al. Clearing for cotton fields was extensive in the early s. In the s, following major floods, congressional actions began to increase federal flood control project construction in the lower Mississippi River valley.

River channelization and flood control structures altered the natural hydrologic regimes of vast floodplain areas. Further conversion for soybeans has had substantial impacts on the bottomland hardwood resource in recent decades, as have urbanization and industrial development. The drained and converted agricultural lands of the Mississippi floodplain retain the natural alluvial soils; it is the hydrology that has been greatly altered.

In these cases, restoration of large areas could be initiated by halting row crop planting and other farmland activities and by closing drainage ditches and small canals. In many areas, the clay soils retard drainage and hold sufficient moisture, so that wetland vegetation would become reestablished. Planting of wetland forest species can accelerate the return to a bottomland forest. It is not realistic, however, to anticipate that true restoration to the original geologic, hydrologic, and biological conditions is possible except in very limited areas.

Most bottomland forest restoration projects focus on techniques of planting and establishing forest species i. Restoration success is commonly judged, at least in the early phases, by the success of tree seedling establishment, and increased timber values and wildlife habitat are often the major goals.

The most successful technique is to plant mixtures of species in blocks or rows. This approach enhances the establishment of species that grow more slowly and compete poorly. A small number of restoration projects have come under the Conservation Reserve Program. Most of these projects began during the late s.

Although some may appear promising in terms of species composition and structure, it is too soon to assess the recovery of other wetland functions. Restoration measures must be carefully designed to retain any remaining values, including functional attributes, wetland soils, biota, and gene pools. In such landscapes, the creation of new wetlands should be explored as an interim measure, to provide habitats for mobile organisms, to determine how well restoration efforts might work in degraded areas, and to retain genetic diversity.

Ecologists predict that early succession communities should be easiest to restore. Hartman calls the smooth cordgrass Spartina alterniflora a good colonizer species, with a ready ability to expand vegetatively. Seneca and Broome in press have evaluated a large number of restoration projects that were studied over a period of several years; for some, the vegetation, invertebrates, and birds are very similar to those found in natural cordgrass marshes.

Broome reviewed wetland restoration projects in the southeastern United States and stated that "a smooth cordgrass stand established on sand in an area where natural marshes are relatively young will likely be comparable to the natural marsh for most measurements in a few years. Similarly, ecosystems dominated by short-lived plants might be more quickly restored than those dominated by long-lived perennials.

Not many wetlands are dominated by annuals, although the vernal pools of California are, and these are persistent communities. Because one of these annual species is endangered the mesa mint, Pogogyne abramsii; cf. Zedler, , there are now attempts to restore its habitat and recover the population to levels that would allow it to persist.

Restoration involves the scraping of shallow impoundments where soils already have a clay layer to retain rainwater. Four years after construction of several dozen pools at Del Mar Mesa San Diego in , successful establishment of mesa mint and its other plant associates is still not at hand P. A series of dry years with less than the average cm annual precipitation has reduced mesa mint densities in natural pools, as well as in artificial ones, so it is not clear if declines would continue in wetter years while a seed bank is still present.

The project might not fail; however, its success seems to depend on the weather—a most unfortunate circumstance in a region with a history of prolonged droughts. The native biota may also set limits on the degree to which predisturbance conditions can be restored.

On the one hand, cattail marshes are a pioneer community with a few plant species that spread rapidly into open areas, including disturbed areas. Such species are preadapted to colonize newly graded sites.

A mature spruce bog, on the other hand, requires decades, if not centuries, to develop in nature. Reconstruction of a forest would take at least as many years as the age of the oldest trees, and replacement of the peat that had accumulated over centuries would take considerably longer. Large numbers of wetland species have received special attention because their populations have dwindled to levels that mark them as endangered.

Careful study of endangered species indicates that they have complex requirements and narrow ecological limits. One particular plant, the salt marsh bird's beak Cordylanthus maritimus ssp. Fink and Zedler, This hemiparasitic annual lives only along the upper margin of salt marshes. Although it can live independently in the greenhouse with water and nutrients added , it grows best when its roots can attach to those of grass species hosts. The plant is not very salt tolerant during germination or growth, nor are the seedlings very tolerant of inundation.

It needs partial shade because plants grow poorly under either open conditions or a dense canopy. Attempts to reestablish populations of this species to restored salt marsh habitats have not yet succeeded B. In addition, field trials suggest that pollinators are limiting and that the small-scale disturbances that create openings in the marsh canopy may be lacking. Small burrowing rodents may have been the natural factor that maintained open patches in the salt marsh.

We cannot yet rely on our ability to restore wetlands that support remnant populations of endangered species, desirable as that may be. Therefore it is not an acceptable mitigation policy to allow further damage to ecosystems that cannot be fully restored to compensate for further losses. Until restoration and creation activities can guarantee full replacement of wetland functions, no further modifications of endangered species habitat should be allowed, because the risk to biodiversity is too great.

Where restoration is intended to. The susceptibility of a site to invasion by exotic or undesirable species is of primary concern because aggressive plant species such as Phragmites australis, Lythrum salicaria , or Typha species may dominate sites intended for other vegetation Larson, ; Odum, Of recent and urgent concern is the spread of three Spartina species S. It is ironic that at least some of these introductions were made deliberately for the purpose of marsh "restoration" Spicher and Josselyn, The exotic plant problem is now considered urgent in the Pacific Northwest.

The state of Washington formed a multiagency working group in to address the problems of habitat alteration and impacts on fisheries and wildlife. They funded a literature review Aberle, and sponsored a scientific workshop in November T. Mumford, Department of Ecology, Seattle, personal communication, to develop a research, management, and control program. Exotic animal species are of equal concern, although their ecology and control mechanisms are little understood.

The zebra mussel invasions of the Great Lakes see Chapter 4 show how quickly a lake system can become dominated by an exotic brought in with ballast water. The recent invasion of San Francisco Bay by an Asian clam, Potamocorbula amurensis , and its current dominance of subtidal habitats F. Nichols, U. Geological Survey, personal communication, July , verify the need for concern. Estuaries are particularly susceptible because of their "seascape linkage" to other coastal areas that are used as ports and where ships disperse foreign organisms and larvae as they discharge ballast water.

The exotics include two plant species Zostera japonica and Sargassum muticum , two fish species, four bryozoans, nine crustaceans, three molluscs, several polychaete species, two coelenterates, and one sponge. Further south, Nordby and Zedler reported the occurrence of two exotic fish species in Tijuana Estuary, another NERR, and Rutherford documented the occurrence of a Japanese mussel, Musculista senhousia, in a San Diego Bay salt marsh restoration site.

In the lower. Mississippi drainage area, the introduced nutria Myocastor coypu has spread throughout swamps and marshes and has retarded reforestation of bald cypress wetlands by feeding on planted cypress seedlings Conner and Toliver, Although some efforts are under way to control invasive plant species e.

Mumford, Washington State Department of Ecology, personal communication, July , there is little possibility of controlling invasive animals, other than by preventing their introduction. As Carlton , p.

These have been so fundamental and pervasive that we may never fully know what the biota of the continental margins looked like before ships and before the movements of commercial fishery products. But with increased awareness of the scale and rate at which introduced species are being transported and released today, we may be able to develop more specific and enforceable controls on the movement and release of species for mariculture, for scientific research, or by ballast water.

Such invaders may pose much greater problems for restoration sites than for natural systems, because disturbed substrates have few defenses against germinating seeds or settling larvae. Legal, political, and economic constraints often govern where restoration can be done and how effective it will be. Legal issues concern land ownership and regulatory processes, discussed below.

Political decisions may determine whether funds are available. Federal land management, water resource development, agricultural, and environmental agencies lack a clear mandate for wetland restoration. Although the lengthy list of restoration strategies posed by the U. Fish and Wildlife Service is encouraging, funding for restoration is not high on the nation's environmental priority list. Wetlands are sensitive to small changes in water supply, hydroperiod, flood cycles, and sediment regimes because they are shallow-water or wet-soil systems.

A persistent change in water depth of 0. Wetlands are thus very susceptible to hydrologic manipulations caused by dams and dikes that reduce inflows, and by irrigation runoff, urban drainage, and wastewater discharges that increase inflows.

Thus, restoration of wetland hydrology must be integrated institutionally, as well as technically, with manipulation of water level and management of hydroperiod. Manipulation of water levels is often the task of one agency. Army Corps of Engineers , whereas restoration efforts are carried out by another e. Fish and Wildlife Service or a state's natural resources department. Integrated water and land use planning is needed to restore the essential surface water elevations, flood cycles, water velocities, and for coastal systems salinity regimes so that the desired wetland ecosystem can be achieved.

Implementing the president's goal of no net loss of wetland acreage and function will not be cheap. Economic constraints will always limit the location, number, and types of projects that can be implemented. The techniques used to restore wetlands vary widely in cost. Wetlands that are near urban centers are the most expensive to restore because of the cost of land. At state and local levels, other demands for land use and funds usually take precedence. Thus, in general, the potential for major restoration projects is currently lower in urban than in rural areas.

Wetlands have been restored in several nonregulatory contexts such as the creation of waterfowl impoundments using water-control structures, the removal of dikes from coastal and estuarine marshes, the blockage of drainage on partially drained agricultural lands no longer used for agricultural purposes, and the grading of gravel pits and other strip-mined lands.

The majority of wetland restoration efforts, however, have occurred as a result of federal, state, or local regulatory actions. In these contexts, private or public landowners seeking permits for various types of development are required either to create, to enhance, or to restore wetlands on-site after damage or to restore wetlands at other sites to compensate for wetland damage at a development site. Few of the Clean Water Act, Section mitigation projects have constituted wetland restoration as defined in this report, and COE and EPA—the two agencies responsible for implementation of the Section program—do not have systematic information about the number of acres of wetlands restored or the effectiveness of particular restoration projects.

In the few states for which Section permit records have been surveyed by EPA, the general finding is that mitigation was not. The site had not been examined to see if restoration had been done, was not monitored, or was shown to differ substantially from what was required in the permit U. For several reasons, the requirements for successful restoration are often unfulfilled in regulatory mitigation contexts:. Wetland restoration projects undertaken as mitigation are, quite often, poorly designed by individuals lacking multidisciplinary expertise.

Hydrology, sediment regimes, control of exotics, and protection of buffers or ecotones are often inadequately addressed. Landowners often prepare the least expensive and least time-consuming restoration plan acceptable to the regulatory agency.

The owners and managers of mitigation wetlands are rarely motivated to complete the restoration or make corrections except those mandated by regulatory requirements. This often means half-hearted attempts to restore or, in some instances, failure to complete a restoration. In contrast, the owners and managers of wetlands in nonregulatory contexts usually have long-term wetland protection and management goals.

Wetlands restored in regulatory contexts are often small in size, widely separated from other wetlands, and threatened by adjacent land uses. Wetlands in nonregulatory contexts are often larger, more closely tied in with existing wetland and aquatic systems, and at least partially buffered from adjacent activities. Wetlands restored in regulatory contexts often receive little management after initial restoration because private and public landowners, who are not motivated to provide such management, may move on or have no legal obligation for such management.

Similarly, the responsible federal agencies do not have staff to assess the adequacy of restoration projects and do not monitor or require permittee monitoring of permit mitigation conditions for sufficient time periods 10 years or longer. As a result, such wetlands may be overrun by exotic species, quickly filled by sediment, polluted, or otherwise misused. For these reasons, wetlands restored in regulatory contexts are much less likely to achieve the restoration goals, and the risk of failure is much greater.

Many things can be done to reduce the risk of failure in a wetland restoration project see Box 6. This is particularly true where landowners are allowed to destroy or damage an existing wetland based on a ''promise" of future restoration.

However, in many instances the goals and success criteria for such restoration are not clearly articulated; mechanisms are not incorporated in the regulatory permit to ensure compliance with restoration plans.

More detailed assessment of function prior to wetland damage or destruction. Complete restoration or creation before allowing damages in mitigation projects. Maintain wetlands and their buffer strips as open space. Avoid wetland alteration or degradation during construction projects. Work with your local municipalities and state to develop laws and ordinances that protect and restore wetlands.

Purchase federal duck stamps to support wetland acquisition. Reduce or eliminate the amount of fertilizers, herbicides and pesticides you apply to your lawn and garden.

Encourage your friends and neighbors to join you in your efforts to protect wetlands in your watershed.