Sunday, June 16, 2013

Barriers for Protection

Increased motor vehicle traffic on the causeways between the mainland and the barrier islands of coastal southern New Jersey is a growing threat to diamondback terrapins. Development on the barrier islands has destroyed most of the sand dunes that originally served as the primary nesting site for terrapins. With the disappearance of sand dunes, females have had to find alternative nesting grounds, primarily the shoulders of roads crossing and adjacent to their native salt marshes.

Embankments of causeways have proved to be a dangerous substitute for sand dunes, resulting in hundreds of terrapin roadkills annually.
     In 2004 researchers from the Wetlands Institute began to install temporary silt fencing along the coastal causeways, in an attempt to reduce road mortality of nesting terrapins in areas known to be major “kill zones.” For three summers, the fencing along Stone Harbor Boulevard reduced terrapin mortality, on average, approximately 84 percent. In 2006, in an attempt to improve the fencing project, a 1,000-foot section of a new fencing material, “Tenax” (a thick, mesh material), was installed to determine its durability in the harsh coastal conditions over the course of a year. The Tenax proved to be durable, so in 2007 the Wetlands Institute installed the year-round Tenax fence along the entire section of Stone Harbor Boulevard. In addition, the fencing project was expanded to include a mile and a half section of Avalon Boulevard (using a combination of both Tenax and silt fence material), which, because the fence was installed in a continuous line with no openings, resulted in a 100 percent reduction of terrapin roadkills.
     By 2009 the Tenax fencing, susceptable to snow damage from plowing and damage from weed whackers, was also showing signs of deterioration. Six-inch corrugated plastic drainage pipe was proven experimentally to be an effective barrier, and in June 2010 over 7,000 feet of corrugated tubing was installed along the Margate Causeway. It proved much quicker and easier to install than either silt or Tenax net fencing.