The Texas Mid-Coast begins near Galveston Bay and ends near Corpus Christi. It is characterized by a relatively narrow band of marsh created in association with the estuaries and bays of minor rivers that drain the region (Moulton et al. 1997). Finally, the Laguna Madre is a shallow embayment stretching along the lower Texas Coast from Corpus Christi to Tamaulipas, Mexico. It is a hypersaline system with few fresh water inputs via rivers, and relatively few openings into the Gulf. Small freshwater wetlands occur immediately inland of the Laguna and provide important dietary fresh water for ducks feeding in nearby hypersaline habitats. Additionally, significant fresh water habitat formerly existed in the now highly agricultural Lower Rio Grande valley (Moulton et al. 1997).
Wetlands along the Gulf coast are declining in size and deteriorating in function resulting from both natural and human induced changes to the system. Historically, the amount of coastal marsh has fluctuated with changes in sea level, delta accretion and subsidence rates, and other factors. In recent history, Louisiana has had approximately 1.36 million ha of coastal marsh. Alarmingly, within the past 50 years, marsh loss rates have exceeded 104 km2/yr with a resultant loss of over 364,219 ha in Louisiana (LCWCRTF 1998). During the 1990s, coastal marsh loss in Louisiana has slowed to an estimated rate of 65-91 km2/year, with projections over the next 50 years that an additional 254,953 ha of marsh, swamps, and islands will be lost, even with completion of planned or proposed large-scale remedial measures (LCWCRTF 1998). Indeed, the LCWCRTF (1998) suggests the entire system of coastal marsh in Louisiana has deteriorated in size and function to the point of being on the verge of collapse, wherein ecological, commercial and cultural values will be lost without rapid and substantial intervention to reverse processes culminating in wetland losses.
Further west in Texas, approximately 1.62 million ha of coastal wetlands existed in the 1950s, but the scope and rate of loss, while substantial, is less severe than in Louisiana. For example, since 1955, approximately 85,264 ha of coastal wetlands have been lost, which is an annual rate of about 23 km2/yr (Moulton et al. 1997). These rates consider changes to coastal marsh as well as to the inland coastal prairies, and techniques utilized to develop these estimates may have underestimated the rate and extent of wetland loss or conversion in Texas (Barry Wilson, pers. comm.).