Estuaries

, Volume 20, Issue 1, pp 1–13

Wetland loss in the Northern Gulf of Mexico: Multiple working hypotheses

  • R. E. Turner
Article

Abstract

I examined four hypotheses about causes for the dramatically high coastal wetland losses (0.86% yr−1) in the northern Gulf of Mexico: an extensive dredged canal and spoil bank network, a decline in sediments in the Mississippi River during the 1950s, Mississippi River navigation and flood protection levees, and salinity changes. Natural factors contributing to these habitat changes include eustatic sea-level rise and geological compaction, which appear to have remained relatively constant this century, although variation does occur. These four hypotheses were tested using data on land-to-water changes in 15-min quadrangle maps inventoried for four intervals between the 1930s and 1990. Land loss rates were directly proportional to changes in wefland hydrology in time and space. A linear regression of the direct losses due to dredging versus the losses due to all other factors (indirect losses) had a zero intercept and a slope that increased with time. The ratio indirect:direct land loss was highest nearest the estuarine entrance. The coastwide patterns of land loss do not appear to be affected by riverine sediment reductions over the last 60 yr. The effects of changes in wetland hydrology from dredging human-made channels and forming dredged spoil banks appear to be the most efficacious hypothesis explaning these dramatic losses. The effects of extensive human-induced changes on this coast have apparently overwhelmed the causal linkages identified in the historical re-constructionist view of deltaic gain and loss that emphasizes the role of mineral sediments. A paradigm shift is therefore proposed that emphasizes a broad ecological view as contrasted to a mostly physical view emphasizing the role of sediment supply in wetland maintenance. In this view, plants are not an ancillary consequence of strictly geological dynamics such as sediment supply but are dominant agents controlling factors relevant to coastal restoration and management efforts.

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Literature Cited

  1. Anonymous. 1995a. Coastal Wetlands Planning, Protection, and Restoration Act: Summary of Priority Lists 1–4. CWPPRA Report Series No. I. Louisiana Department of Natural Resources, Baton Rouge, Louisiana.Google Scholar
  2. Anonymous. 1995b. A White Paper: The State of Louisiana's Policy for Coastal Restoration Activities. Signed by the Governor, the Secretary and Assistant Secretary of the Louisiana Department of Natural Resources, and the Executive Assistant of the Governor's Office of Coastal Activities. Dated 24 April, 1995. Governor's Office of Coastal Activities, Baton Rouge, Louisiana.Google Scholar
  3. Bass, A. and R. E. Turner. In press. Relationships between salt marsh loss and dredged canals in three south Louisiana estuaries.Journal of Coastal Research 13:Google Scholar
  4. Baumann, R. H. andR. E. Turner. 1990. Direct impacts of outer continental shelf activities on wetland loss in the central Gulf of Mexico.Environmental Geology and Water Resources 15: 189–198.CrossRefGoogle Scholar
  5. Boesch, D. F., M. N. Josselyn, A. J. Mehta, J. T. Morris, W. K. Nuttle, C. A. Simenstad, and D. J. P. Swift. 1994. Scientific Assessment of Coastal Wetland Loss, Restoration and Management in Louisiana.Journal of Coastal Research, Special Issue. No. 20.Google Scholar
  6. Britsch, L. D. andJ. B. Dunbar. 1993. Land loss rates: Louisiana Costal Plain.Journal of Coastal Research 9:324–338.Google Scholar
  7. Brush, G. S. 1984. Patterns of recent sediment accumulation in Chesapeake Bay (Virginia-Maryland, U.S.A.) tributaries.Chemical Geology 44:227–242.CrossRefGoogle Scholar
  8. Cahoon, D. R. andR. E. Turner. 1989. Accretion and canal impacts in a rapidly subsiding wetlands. II. Feldspar marker horizon technique.Estuaries 12:260–268.CrossRefGoogle Scholar
  9. Dahl, T. E. 1990. Wetland losses in the United States 1780s to 1980s. United States Department of Interior, Fish and Wildlife Service. Washington, D.C. mimeo report.Google Scholar
  10. Daigh, F. C., D. MacCreary, andL. A. Stearns. 1938. Factors affecting the vegetative cover of Delaware marshes.Proceedings of the New Jersey Mosquito Extermination Association 25:209–216.Google Scholar
  11. Faber, P. 1982. Muzzi marsh restoration, a mitigation project, p. 100.In M. Josselyn (ed.), Wetland Restoration and Enhancement in California. California Sea Grant Program, Report T-CSGCP-007. University of California, La Jolla, California.Google Scholar
  12. Fisk, H. N., E. McFarlan Jr.,C. R. Kolb, andL. J. Wilbert, Jr. 1954. Sedimentary framework of the modern Mississippi delta.Journal of Sedimentary Petrology 24:76–99.Google Scholar
  13. Gagliano, S. 1994. An Environmental-Economic Blueprint for Restoring the Louisiana Coastal Zone: The State Plan. Governor's Office of Coastal Activities and the Wetland Conservation and Restoration Task Force, Baton Rouge, Louisiana.Google Scholar
  14. Gilmore, R. G., D. W. Cooke, andC. J. Donohoe. 1981. A comparison of the fish populations and habitat in open and closed salt marsh impoundments in east-central Florida.Northeast Gulf Science 5:25–37.Google Scholar
  15. Johnson, J. E., J. D. Rives, and D. M. Soileau. 1990. Geologic review: Better regulation through interagency cooperation, p. 4264–4277.In O. T. Magoon, H. Converse, D. Miner, L. T. Tobin, and D. Clark (eds.), Proceedings of Coastal Zone '89 Symposium, American Society of Civil Engineers, New York.Google Scholar
  16. Josselyn, M. andR. Perez. 1982. Salt marsh restoration from salt evaporation ponds: Vegetation establishment and sediment properties. p. 100.In M. Josselyn (ed.), Wetland Restoration and Enhancement in California. California Sea Grant Program, Report T-CSGCP-007. University of California, La Jolla, California.Google Scholar
  17. Kesel, R. H. 1988. The decline in the suspended load of the lower Mississippi River and its influence on adjacent wetlands.Environmental Geology and Water Science 11:271–281.CrossRefGoogle Scholar
  18. Martin, J. C. andS. Serdengecti. 1984. Subsidence over oil and gas fields.Reviews in Engineering Geology 6:23–34.Google Scholar
  19. Meade, R. H. and R. S. Parker. 1984. Sediments in rivers of the United States. National Water Supply Summary.United States Geological Survey Water-Supply Paper 2275.Google Scholar
  20. Monte, J. A. 1978. The impact of petroleum dredging on Louisiana's coastal landscape: A plant biogeographical analysis and resource assessment of soil bank habitats in the Bayou Lafourche Delta. Ph.D. Dissertation, Louisiana State University, Louisiana.Google Scholar
  21. Neill, C. andR. E. Turner. 1987. Backfilling canals to mitigate wetland dredging in Louisiana coastal marshes.Environmental Management 11:823–836.CrossRefGoogle Scholar
  22. Roman, C. T., W. A. Niering, andR. S. Warren. 1984. Salt marsh vegetation change in response to tidal restriction.Environmental Management 8:141–150.CrossRefGoogle Scholar
  23. Sasser, C. E., M. D. Dozier, andJ. G. Gosseline. 1986. Spatial and temporal changes in Louisiana's Barataria Basin marshes, 1945–1980.Environmental Management 10:671–680.CrossRefGoogle Scholar
  24. Slobodkin, L. B. 1988. Intellectual problems of applied ecology.BioScience 38:337–342.CrossRefGoogle Scholar
  25. Stumpf, R. P. 1983. The process of sedimentation on the surface of a salt marsh.Estuarine, Coastal and Shelf Science 17:495–508.CrossRefGoogle Scholar
  26. Suhayda, J. N. 1987. Subsidence and sea level, Chapter 10.In R. E. Turner and D. R. Cahoon (eds.), Causes of Wetland Loss in the Coastal Central Gulf of Mexico. Vol. 2: Technical Narrative. Final report submitted to Minerals Management Service, Contract No. 14-12-001-30252. OCS Study/MMS 87-0119. New Orleans Louisiana.Google Scholar
  27. Swenson, E. M. andR. E. Turner. 1987. Spoil banks: Effects on a coastal marsh water level regime.Estuarine, Coastal and Shelf Science 24:599–609.CrossRefGoogle Scholar
  28. Turner, R. E. andJ. G. Gosselink. 1975. A note on standing crop ofSpartina alterniflora in Texas and Florida.Contributions in Marine Science 19:13–18.Google Scholar
  29. Turner, R. E. 1987. Relationships between canal and levee density and coastal land loss in Louisiana.United States Fish and Wildlife Service Biological Report. 85(14).Google Scholar
  30. Turner, R. E. 1990. Landscape development and coastal wetland losses in the northern Gulf of Mexico.American Zoologist 30:171–197.Google Scholar
  31. Turner, R. E. 1991. Tide gauge records, water level rise and subsidence in the northern Gulf of Mexico.Estuaries 14:139–147.CrossRefGoogle Scholar
  32. Turner, R. E. andY. S. Rao 1990. Relationships between wetland fragmentation and recent hydrologic changes in a deltaic coast.Estuaries 13:272–281.CrossRefGoogle Scholar
  33. Turner, R. E., E. M. Swenson, andJ. M. Lee. 1994a. A rationale for coastal wetland restoration through spoil bank management in Louisiana.Environmental Management 18:271–282.CrossRefGoogle Scholar
  34. Turner, R. E., J. M. Lee, andC. Neill. 1994b. Backfilling canals as a wetland restoration technique in coastal Louisiana.Wetlands Ecology and Management 3:63–78.CrossRefGoogle Scholar
  35. Wiseman, W. J.., Jr.E. M. Swenson, andJ. Power. 1990. Salinity trends in Louisiana estuaries.Estuaries 13:265–271.CrossRefGoogle Scholar

Copyright information

© Estuarine Research Federation 1997

Authors and Affiliations

  • R. E. Turner
    • 1
  1. 1.Costal Ecology Institute and Department of Oceanography and Coastal SciencesLouisiana State UniversityBaton Rouge

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