Rising sea level redefines N.C. coast

If climate predictions hold, the transformation of islands and rivers will speed up

In North Carolina, global warming isn't a future worry. It's already lapping ashore.

Nags Head Mayor Renee Cahoon sees all the proof of climate change she needs at the end of Old Oregon Inlet Road. The street once led to rows of oceanfront houses. Now it ends suddenly in bulldozed piles of sand.

Some beach erosion occurs naturally, and development near the ocean tends to make it worse. But some scientists think erosion has grown more pronounced in recent years as the sea level has risen and storms increased. On some days, stretches of Nags Head have no dry beach, and visitors have to sit under the front-row houses at high tide. The resort that once thrived by the sea is being swallowed by it.

"We are losing the town," Cahoon said. "As sea level rises, our tax base goes away."

Other, more subtle changes are under way along the coast, not just on the fragile barrier islands. As salt water pushes farther upriver, some rivers are widening into estuaries, tidal bodies of water where fresh and salt water mix. Freshwater swamps are changing to salt marsh.

"The shore is the line of conflict where this crisis is taking place," said geologist Stan Riggs, designated a distinguished research professor at East Carolina University. "We can't think we're going to hold the line."

Scientists predict that the buildup of carbon dioxide gas in the atmosphere will lead to higher global temperatures. That warming will cause seas to rise faster and increase erosion driven by storms.

Changes are already occurring. The world's oceans rose about 6 inches to 8 inches during the 20th century. In North Carolina, the ocean has grown higher by about 8 inches in the past century, because much of the coast is also slowly sinking as the land settles.

A panel of international scientists projects the seas will rise 7 to 30 inches in the next century unless there is a substantial reduction in the emission of man-made greenhouse gases such as carbon dioxide. Those gases spew from our cars, power plants and appliances, accumulating in the atmosphere and trapping heat.

Hundreds of scientists from 40 countries this year proclaimed that climate change is "unequivocal." Global air and water temperatures are inching up, causing seas to warm and expand, and polar ice to melt -- triggering higher sea levels.

There's still debate over how much of the observed change in temperature is due to man-made carbon dioxide and how much comes from the natural cycles of weather. But there's little argument that North Carolina's water, air, food and land are being altered. And more rapid change is predicted.

Swamps turn salty

Gray trunks of dead cypress trees line the shore of the Northeast Cape Fear River a few miles upstream from downtown Wilmington. The trees have been essentially drowned by salt water. Tupelo gum, red maples and other tree species have already disappeared, unable to tolerate the chemical reactions of salt water in soil.

Rising sea levels are pushing high ocean tides of salt water farther up the river.

The soil, exposed to salt, gradually disintegrates, leaving tangles of gnarled cypress roots clinging to air where a riverbank once stood. The disintegrating soil releases carbon dioxide into the atmosphere, adding to global warming. As the trees die, a freshwater swamp changes into a salt marsh.

As the bank crumbles, the river is broadening and transforming into an estuary such as the Pamlico Sound or Chesapeake Bay. The Cape Fear River basin has 200,000 acres of timber that will eventually turn into marsh, said Courtney Hackney, a marine biologist at UNC-Wilmington.