Landscape Development and Coastal Wetland Losses in the Northern Gulf of Mexico

The causes of the extensive (0.86%/yr; 288,414 ha/yr) and welldocumented dramatic and accelerating rate of coastal wetlandloss in the northern Gulf of Mexico were investigated by aninterdisciplinary university research team to discern the roleof outer continental shelf development. The landscape changesand potential causal agents are emphasized herein. Natural drivingfactors include sea level rise and geological compaction, whichappear to remain constant this century, and sediment supplyfrom the Mississippi River which has declined by 50%,since the1950s. Man-made influences include hydrologic changes from riverdiversions, flood protection levees, an extensive canal andspoil bank network, belowground fluid withdrawal and accidentaland intentional impoundments. Wetland loss is not simply a geologicalphenomenon. Wetland plants hold sediments together, add to verticalaccretion rates, withstand storm winds and waves, and assistin sediment trapping. Plant physiologic stress is documentedwhere hydrologic changes occur, and much of the wetland losscould be attributed to the effects of soil waterlogging on plants,not to sediment deprivation.