The western shoreline of Padre Island at the north end of the Padre Island National Seashore is eroding. Coastal researchers generally attribute barrier island erosion to sea level rise, local subsidence and damming of rivers which reduces sediment loads to coastal areas, but other causes seem more logical at this site. Researchers studied aerial photographs dating from 1941 to 1987 to document changes in shoreline shape and position. They traced shoreline positions onto a mylar overlay and compared shoreline positions in subsequent photographs, relative to the 1987 shoreline position, along 10 transects.
Shoreline retreat is a recent phenomenon.
From 1941 to 1979 shoreline outbuilding, not retreat, dominated the area. The shoreline built out faster during droughts, possibly because droughts enlarged preexisting migrating dune fields and supplied more wind-blown sand to the west side of the island. Origin of the dune fields is unclear but they possibly formed in the late 1800s or early 1900s as overgrazing and grass burning by ranchers and a series of droughts destroyed island grasslands. In the past few decades, higher average rainfall and the cessation of ranching on the National Seashore have limited the size of dune fields and reduced the supply of wind-blown sand to the shoreline. This encourages minor erosion because sands washed away are not easily replaced.