Quarterdeck Volume 5, Number 2, Summer 1997
Can the loss of Texas coastal wetlands be halted... or reversed?
Mead A. Allison
A bold experiment getting underway later this year at Galveston Island State Park may have far reaching implications for the future health of Texas coastal wetlands. The project, carried out jointly by the Texas Parks and Wildlife and the U.S. Fish and Wildlife Service, will recreate or restore 303 hectares (749 acres) of degraded saltmarsh and seagrass habitat in the park. This wetland restoration is the largest ever attempted in Texas and the second largest (after one in Louisiana) in the United States. The restoration is in response to a precipitous decline in the park's wetland area from over 404 hectares (1,000 acres) the mid-1950s to less than 162 hectares (400 acres) today.
The wetlands loss at Galveston Island State Park is emblematic of a disturbing nationwide trend. Studies have shown that more than half of the wetland area in the United States has disappeared in this century. In Texas, a recent report* estimates that there were 1.7 million hectares (4.1 million acres) of wetlands in the state in the 1950s but less than 1.3 million hectares (3.3 million acres) by the early 1990s. Estuarine (saltwater) wetlands declined from 66,776 hectares (165,000 acres) to 52,773 (130,400 acres) during the same period. These coastal wetlands include unvegetated intertidal flats as well as emergent salt, brackish, and intermediate marshes that are flooded periodically by water with salinity greater than 0.5 parts per thousand.
The majority of the estuarine wetlands loss in Texas (14,205 hectares or 59%) occurred in the Galveston Bay system according to a Galveston Bay Estuary Program (GBEP) report. This report attributes the accelerated loss of marshes around Galveston Bay relative to the rest of the Texas coast to subsidence induced by withdrawal of groundwater, oil, and gas. Land subsidence of 30 to 180 centimeters in the bay system since the 1940s, combined with rising sea level, has lowered marsh elevations, exposing plants to ever higher salinities and wave attack. This process converts marsh areas to open water habitat. Other marsh areas have been filled and converted to upland habitat for agricultural, transportation, industrial, residential or commercial reasons.
There is increasing awareness of the vital role coastal wetlands play in the health and productivity of estuaries. An estimated 80% of commerical and recreational coastal fisheries in the United States rely on wetlands as spawning areas, nurseries, and food sources. Approximately 95% of marine species in Texas bays and the Gulf of Mexico depend on wetlands in some portion of their life cycle. Coastal wetlands also provide important habitats for a host of other birds, mammals, and aquatic plants. The marshes that fringe Texas estuaries also serve as filters that remove pollutants and absorb nutrients entering the estuary as runoff. The dense stem networks of estuarine plants form a natural storm barrier, trapping sediment and retarding the flow of floodwater, while their root mats limit shoreline erosion.
In recognition of their value, the Clinton Administration has set a goal of no net loss of public and private wetlands nationwide. The plan calls for protection of threatened areas, mainten-ance of existing tracts, and restoration of degraded or lost wetlands. Achieving the last goal will require wetlands restoration on a scale not yet attempted. In the Galveston Bay system for instance, GBEP's Galveston Bay Plan calls for the creation or restoration of 6071 hectares (15,000 acres) of additional wetlands by 2005. The project at Galveston Island State Park, and simultaneous smaller projects at Pierce Marsh and in West Bay near I-45, will be a proving ground to test methodologies for future restoration efforts in Texas and elsewhere. Two million dollars of financing for the project comes from the Apex Restoration Fund, established from a compensatory damage award after the 1990 Apex Barges oil spill, as well as matching grants obtained through the federal Coastal Wetlands Conservation and Restoration Act.
While subsidence is clearly the major cause of wetlands loss in Galveston Island State Park, the restoration project will attempt to identify and control additional detrimental factors such as nearby development, chemical stresses, natural erosion and salt intrusion. The preliminary plan calls for complete re-engineering of the wetlands habitat to restore it to a pre-1970s state. This includes using material dredged from the bay floor and hauled in on trucks to restore the elevation of marsh substrates and tidal lagoons. Approximately 40 hectares (100 acres) of new intertidal marsh and 17 hectares (41 acres) of seagrass beds will be planted. The goal will be to reproduce the ecological zones characteristic of natural coastal marshes that show a gradation from Smooth Cordgrass (Spartina alterniflora) in the low marsh, to brackish areas colonized by Black Needlerush (Juncus romerianus) and Marshhay Cordgrass (Spartina patens) with intermediate areas populated by bulrushes and cattails. The proposed plan also includes provisions to construct wave-stilling barriers to protect newly planted areas and to funnel sediment to vegetated areas to reduce future degradation.
*Texas Coastal Wetlands: Status and Trends, Mid-1950s to Early 1990s, produced jointly by the U.S. Fish and Wildlife Service and Texas Parks and Wildlife. To receive a free copy of the report see the Texas General Land Office web site at: http://www.glo.state.tx.us/wetnet/tcwreport.html
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Last updated September 1, 1997