Can Science Save Coastal Development?
Nicholas School Faculty Members Play Key Roles in Documenting Threats and Offering Ways to Avoid Them p.2
Some experts question whether beach nourishment is sustainable or whether the sand will simply be washed away in a few seasons. Orbach says that depends on the location. “Bogue Banks is a good candidate for nourishment because it has a good source of sand nearby, it’s high in elevation, and it has an east-west orientation that is less susceptible to erosion,” he says. “Other sites might have to be nourished so often and at so great a cost that it’s not worth it. Science can give us data and information, but the tradeoffs between preservation of natural environments and human habitation—whether any particular action is ‘worth it’ —has to be made through the governance process.”
A man who has written many op-eds questioning the wisdom of beach nourishment, Orrin Pilkey, James B. Duke Professor Emeritus of Earth Sciences, is considered one of the nation’s experts on coastal geology. He has coauthored two dozen books and more than 150 technical publications on the subject.
Pilkey has warned for decades that barrier islands, such as North Carolina’s Outer Banks, are constantly migrating and, therefore, poor places for development. Experts credit his research for the passage of North Carolina’s ban on hardened structures on the coast.
Pilkey heads the Program for the Study of Developed Shorelines (PSDS) within the Nicholas School’s Division of Earth and Ocean Sciences. Among other resources, PSDS maintains a regularly updated database on beach nourishment projects around the country. The database contains locations, primary finding sources, volumes of sand delivered, lengths and costs—everything officials might need to determine the viability of a nourishment project.
“It’s the most comprehensive table of beach nourishment in the country,” says Andy Coburn, PSDS assistant director.
Despite the availability of this and other information to guide sustainable development, Pilkey doubts it can prevail over the political, economic, and emotional pressures to build and stay on the beaches.
“We’re trying hard to bring science into coastal management, but we find ourselves stymied by a fundamental lack of interest in science,” he says. Pilkey laments that even in a state like North Carolina that has sound laws to govern coastal development, there are too few people to enforce them.
While Pilkey’s eyes are on the geology of the nation’s shorelines, Larry Crowder, Stephen Toth Professor of Marine Biology, keeps his focus on the fish and shellfish that inhabit the estuaries. Their fates, too, are affected by agriculture and development, not just along the coast but also hundreds of miles upstream.
“Nutrients that leak off the land enter into the watershed, and when they flow into the estuaries, they stimulate algal production,” Crowder explains. “What algae isn’t eaten by aquatic life drops to the bottom and decomposes, using up oxygen in the process. This state of hypoxia can have adverse effects on fish and shellfish populations.”
Hypoxic events occur around the world, but are especially bad in the Gulf of Mexico, where nutrients flowing down the Mississippi River from upstream farms and cities are creating an ever-expanding “dead zone.” Crowder and his associate, Kevin Craig, have been examining the link between hypoxia and the numbers and distribution of fish and shrimp in the Gulf.
“The dead zone forms every spring when large amounts of freshwater come down the Mississippi,” Crowder says. “All the critters that were on the bottom move to the edge of the zone and accumulate in high densities. That crowding affects physiological health.”
Crowder and Craig have observed that shrimp on the edge of the dead zone accumulate fewer lipids, delaying the molting of shells and reducing growth rates. This potentially translates into fewer and smaller shrimp, which could be bad news for the fishing industry.
Further, shrimp suffer more predation when they are crowded together. Sea turtles gather on the edge of the dead zone to feed on the shrimp, as do commercial fishermen. The latter may catch more shrimp, but they also haul in many more sea turtles than usual in their trawling nets. This leads to increased mortality among these already endangered reptiles.
“If we made better use of the land, we’d be losing fewer nutrients into the water,” Crowder says. “Government is working with the people in the Mississippi watershed, aiming for a 30 percent reduction in nitrogen loading. It’s too early to tell if it’s going to work.”
Photos: Larry Crowder; William Kirby-Smith; Mike Orbach; Orrin Pilkey; Curt Richardson