Wetlands Ecology and Management 8: 293–294, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. The U.S. Government right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.

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Preface W.J. Streever U.S. Army Engineer Research and Development Center, Waterways Experiment Station, Vicksburg, Mississippi 39180, U.S.A.

Dredging projects can result in the accumulation of thousands of cubic meters of sediment. Often, this material is simply redeposited in deep water or in socalled ‘confined disposal facilities.’ However, in many circumstances dredged material can be used in what have been called ‘beneficial use projects,’ including such things as creation of islands or filling of mine pits. Another beneficial use option involves placing dredged material on shallow bay bottoms to create intertidal wetlands. This special issue of Wetlands Ecology and Management, started when Gene Turner was editor-in-chief of the journal (and completed with his editorial assistance), brings together a collection of five papers representing current thinking regarding creation or restoration of Spartina alterniflora (smooth cordgrass) salt marshes using dredged material. Many kinds of marshes and forested wetlands are created or restored using dredged material, both in the United States and elsewhere, but this special issue concentrates on S. alterniflora dredged material marshes of the Gulf and East coasts of the United States in an effort to limit discussions to a specific type of wetland. Despite this narrow focus, these papers will contribute to improved overall understanding of wetland creation and restoration in general. The papers focus on two central questions. First, how do dredged material marshes compare to natural marshes? And second, do dredged material marshes follow a developmental trajectory leading to increased similarity with natural marshes over time? Results of comparison studies are clear: some attributes of dredged material marshes are similar to nearby natural reference marshes, while other attributes are substantially different. This conclusion is in keeping with findings from studies of other approaches to wetland creation and restoration (see, for example, Streever et al., 1996; and Zedler, 1999). Results of efforts to assess wetland development over time are somewhat less clear. On the one hand, some evidence exists

showing that certain marsh attributes continue to develop over many years. Most notably, work by Shafer and Streever (pp. 353–366) shows that belowground biomass appears to increase with marsh age. Also, long-term studies of individual sites seem to show developmental trajectories (Craft et al., 1999). However, many marsh attributes do not continue to develop over long periods. Instead, they develop rapidly and then appear to stabilize, as shown by Alphin and Posey (pp. 317–325) and Minello (pp. 327–341). Also, because of high intersite and interannual variability, continual development of dredged material marshes over time is not equivalent to increasing similarity with natural reference marshes, as noted in Streever’s review (pp. 295–316). Papers by Shafer and Streever (pp. 353–366) and Delaney et al. (pp. 343–352) compare geomorphological attributes of dredged material and natural marshes. Among other things, these papers illustrate the difficulties that arise from attempts to quantify what at first appear to be simple geomorphological characteristics, such as edge:area ratios. Clearly, the approaches adopted in these two papers are not identical, and, likewise, the results are not in complete agreement. Nevertheless, results offer insights that may contribute to future marsh design. The papers in this special issue have important implications for natural resource managers. Although it is disappointing to see that dredged material marshes do not provide the full suite of structures and functions found in natural marshes, managers should avoid focusing exclusively on differences. For many wetland projects, perfect similarity between dredged material and natural reference wetlands is not necessary. Often, dredged material wetlands are far more attractive than other dredged material placement options in terms of environmental benefits, even if perfect similarity with a natural marsh cannot be achieved. Also, managers should bear in mind that some project objectives and

294 performance standards are more likely to be achieved than others, and that monitoring a single wetland attribute (plant cover, for example) will not provide a complete picture of wetland development. Where should dredged material wetland research go from here? There is little need for more studies assessing plant establishment methods. Also, further comparisons of biological communities found in individual dredged material and natural marshes are of limited value. There are, however, few studies comparing populations of dredged material and natural marshes, and no studies providing long-term data on populations of dredged material and natural marshes. Also, there are geographical gaps in comparison studies. For example, there are few published studies on dredged material wetlands in Louisiana, despite an abundance of dredged material wetlands in the state (one notable exception is Poach and Faulkner (1998)). There is a need to develop meaningful geomorphological measurements that can be used to compare marshes and to link geomorphological features to biological communities. Lastly, little information is available on the ability of dredged material wetlands to improve water quality. Waterborne transport continues to be one of the least expensive methods of transporting commodities, and there is no reason to believe that dredging requirements will decrease in coming decades. As the need to replace lost wetland habitat becomes more pressing, dredged material will be used more often to create or restore wetlands. The challenge for wetland researchers and managers is to see beyond currently available techniques that lead to robust stands of plants and to develop new methods that improve overall similarity between dredged material wetlands and natural wetlands.

References Craft, C., Reader, J., Sacco, J.N. and Broome, S.W. 1999. Twentyfive years of ecosystem development of constructed Spartina alterniflora (Loisel) marshes. Ecological Applications 9: 1405– 1419. Poach, M.E. and Faulkner, S.P. 1998. Soil phosphorus characteristics of created and natural wetlands in the Atchafalaya Delta, LA. Estuarine, Coastal and Shelf Science 46: 195–203. Streever, W.J., Portier, K.M. and Crisman, T.L. 1996. A comparison of dipterans from ten created and ten natural wetlands. Wetlands 16: 416–428. Zedler, J.B. 1999. The ecological restoration spectrum. In: Streever, W.J. (ed.), An International Perspective on Wetland Rehabilitation. pp. 301–318. Kluwer Academic Publishers, Dordrecht, The Netherlands.