By Steven Bradley
Photography by Josh Wilson, Tom O’Halloran & Brian Williams
Thirty years after Hurricane Hugo, Clemson’s Baruch Institute is still in the trenches of hurricane research
At 2 parts per thousand of salt water, the bald cypress are already severely stressed. Once the chloride concentration reaches 4, the trees are on their way out. And those, the species that lend cypress swamps their name for their ubiquity, are the last to go. The swamp tupelos, red maples and black gums have long since succumbed. By 5, the tidal freshwater forested wetland ecosystem is gone, replaced by salt marsh or open water.
Salt water encroachment due to sea level rise — driven by a more variable global climate system, along with tidal surges caused by hurricanes that carry salt water into the forest to infiltrate the soil — is killing off coastal forests across the American Gulf and Atlantic coasts.
While the death of a swamp might not seem like cause for concern to some, the wading birds, fish, reptiles, deer and bear that call it home are sure to have a different view. Those who care about preserving an iconic part of the coastal landscape of the Deep South, too.
But as coastal forests fight this losing battle against the sea, Clemson University researchers at the Belle W. Baruch Institute of Coastal Ecology and Forest Science in Georgetown, S.C., are working to level the playing field.
When Hurricane Hugo crashed into the South Carolina coast as midnight approached on Sept. 21, 1989, its maximum sustained wind speed of just over 135 mph is the highest on record for a hurricane in South Carolina, according to the state climatology office. Massive 20-foot storm tides — the highest ever recorded on the East Coast — slammed Bulls Bay just north of Charleston.
Rising sea level in low-lying ecosystems along America’s southeastern Atlantic and Gulf coasts are converting freshwater forested wetlands into salt marsh, leaving behind what scientists have dubbed “ghost forests.” And at Winyah Bay in northeastern South Carolina, sea level is rising by an average of 3-4 millimeters per year. That translates to about 24 centimeters — not quite 10 inches — over 60 years.
While less than a foot across six decades may seem insignificant, remember why it is called the South Carolina Lowcountry. Large infrequent disturbances such as hurricanes also significantly alter coastal forests through damaging winds and salt water carried inland with the storm surge. Hurricanes are increasing in both frequency and intensity with a more variable climate system, and, in turn, scientists expect increasing sea level rise and enhanced opportunity for saltwater intrusion.
And while sea level rise is an expected consequence of climate change — more intense storms push salt water further inland, while increasing droughts slow the outbound flow — it’s also a result that could have devastating consequences to ecosystems across the southeastern U.S.
Sea level is expected to rise 0.48 meters with a range between 0.11 and 0.77 meters by the year 2100, but some believe that estimation may be conservative and the range could be as large as from 0.5 to 1.4 meters. Approximately 58,000 square kilometers, more than 22,000 square miles, of land along the Atlantic and Gulf coasts lies below the 1.5-meter contour, dangerously close to the tipping point where land begins being reclaimed by sea.
“In either case, sea level rise under a changing climate is of a great concern to low-lying states in the southeastern United States with large coastal wetlands, including North and South Carolina, Louisiana, Florida and Texas,” Baruch researchers Tom Williams, Alex Chow and Bo Song wrote in a 2012 research report.
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