DURHAM, N.C. – For the last quarter-century, through fair weather and foul, Duke University geologist Orrin Pilkey has been warning that it's a bad idea to build on vulnerable barrier islands like North Carolina's Outer Banks.
Development pins the islands in place, rather than allowing them to move shoreward in response to rising sea levels, his many books and guest editorials have argued.
In his latest book, The Rising Sea (Aug. 2009, Island Press), Pilkey, a retired James B. Duke Professor of Geology at Duke's Nicholas School of the Environment, and his co-author, fellow geologist Rob Young of Western Carolina University, argue that the latest obvious evidence of sea level rise due to global warming has ended the debate.
With a rise of at least three feet expected by many scientists by the year 2100 "there will be no more development on barrier islands unless they are heavily armored with seawalls on all sides," Pilkey says. "Some states like Florida are in particularly bad shape because they have virtually hundreds of miles of high-rise-lined shorelines that can't be moved. Looking globally, the places that are most endangered are the river deltas of the world” such as those of the Mississippi, the Nile, the Niger, the Ganges and the Irawaddy. On the Ganges delta, 15 million people live below a three foot elevation.
"People living on coral atolls in the mid-Pacific and the equivalent Maldives in the Indian Ocean are already in trouble and starting to be moved," Pilkey notes. So too are Eskimos near the Arctic Circle in Alaska whose remote villages are no longer protected from waves by sea ice.
Rising sea levels will also affect big cities along the U.S. east coast from Boston to Miami, starting with subways and sewer systems. Well inland, in states with shallow sloping coastal plains, farmers will begin battling salt water intrusion in fields that no longer drain properly.
"Though numbers would vary highly from one spot to another, in some parts coastal North Carolina a one foot sea level rise could move the shoreline back two miles, and a three foot rise, six miles. And we should really plan for the possibility of twice that," Pilkey says.
While some have proposed mounting "Dutch-like gates" at tidal inlets to block ocean encroachment, that won't work, Pilkey says. "You have to have something to attach those to, and the barrier islands will no longer be there."
One big uncertainty is how much of the vulnerable ice sheets in Greenland and Antarctica will collapse and melt during the 21st century. After surveying the possibilities and the consequences, Pilkey and Young’s conclusions are not comforting.
"In our view, a 3.3-foot sea level rise in this century would be a disaster, a 7-foot sea level rise would be a catastrophe and a higher rise is not out of the realm of possibility," they write.
Young, Pilkey's former graduate student, is a professor of geosciences at Western Carolina who now directs the program for the Study of Developed Shorelines that Pilkey began at Duke.