Habitat Priority Problems
Based upon aerial photo interpretation, the area of estuarine wetlands in the Galveston Bay system decreased by approximately 35,000-45,000 acres from the mid-1950s to the mid-1990s, or by about 20 to 27 percent. The leading causes of wetland losses in the Galveston Bay system include relative sea-level rise and land use conversion to agricultural, urban, industrial, and transportation purposes. Other causes include dredge-and-fill activities and large-scale shoreline modification projects. A large portion of the overall losses in wetlands can be attributed to the loss of fresh marshes. Overall, the rate of estuarine wetland loss in Galveston Bay is higher than the national average.
Approximately 80 percent of the bay's historical submerged aquatic vegetation, including seagrasses, have been lost since the 1950s. A complex and interactive set of causes, which includes dredging, subsidence, hurricane effects, shoreline development, and boat traffic are the reasons for this loss.
Even though there is disagreement on the total acreage of oyster reef present in the 1950s, it can be safely concluded that the location and areal extent of Galveston Bay oyster reefs has changed considerably by modern human activities. From about 1900 until 1969, oyster shell from reefs and islands in the bay was removed for construction material and the chemical industry, particularly during the post-World War II boom years. While changes have occurred at the hands of humans, no evidence exists for a substantial impact by the commercial oyster fishery on the number and size of oyster reefs in the bay.
Within the Galveston Bay estuary, the introduction and proliferation of exotic species has contributed to the degradation of some portions of the estuarine habitat and threatens many native plant and dependent animal species. Significant populations of nutria, a large beaver-like rodent that migrated from Louisiana where they were imported for their fur during the 1930's, strip vegetation within fresh marsh and brackish marsh. Grass carp, which were introduced to control aquatic vegetation, have established a reproducing population in the Trinity River and have dispersed to many tributaries of the estuary and may be feeding on emergent marsh vegetation. Giant salvinia, an aquatic plant capable of completely filling water bodies, is present in the lower Galveston Bay watershed. The Chinese tallow tree is an aggressive invader of the coastal prairie; it quickly replaces native vegetation while providing little wildlife value.
See more information on priority problems related to Galveston Bay habitat in Chapter Seven of The State of the Bay. See Solutions.