By ELISE R. HUGUS
The impacts of climate change are coming soon, to a coastal property near you.
A conference at the Woods Hole Oceanographic Institution last week focused on ways to manage shoreline change in the next century, as sea level climbs by an estimated three feet.
Due to climate change, global sea level is rising by an average of three millimeters per year, said E. Robert Thieler, a US Geological Survey researcher, at a public forum on the issue entitled "Where Land & Sea Meet."
While that number may seem minuscule, coastal communities such as Falmouth will feel the effects of sea level rise sooner than many residents think.
"We’re about to enter a different sea level rise regime, and it’s going to lead to different coastal responses," said Dr. Thieler, who is a Falmouth resident.
With a three-foot sea level rise, downtown Falmouth will be subject to flooding, and the dune erosion that has plagued West Falmouth could further degrade the town’s beaches, he said.
In January, Dr. Thieler co-authored a paper published by the US Climate Change Science Program showing that infrastructure and ecosystems in coastal communities are in a highly vulnerable position, as storms increase in number and intensity.
While that paper focused on the mid-Atlantic region, the implications are similar on Cape Cod, which could suffer from long-term impacts on tourism, transportation, and fisheries, Dr. Thieler said.
Bluff erosion and island breaching are already a reality on the Lower Cape, he said, adding that a critical "threshold crossing" will take place as barrier islands and wetlands disappear, causing "irreversible damage" to the coastline.
Andrew Ashton, a WHOI coastal geomorphologist, said that the era of passing on a family beach house over generations may be a thing of the past. "It’s a changing paradigm, where living along the coast is a temporary thing," he said.
A member of the audience questioned the implication that humans are responsible for climate change. Mark Siddall, of the University of Bristol, England, said that the unequivocal opinion among scientists is that increasing concentrations of greenhouse gases are causing the polar ice caps to melt and ocean water to expand as global temperatures rise.
Research shows that resulting changes in ocean currents have already shifted climate systems, leading to sea level rise, irregular patterns of species migration, and the spread of disease.
"The data gives us a baseline. We know what the natural variability is, and we know we left it at the same time we were industrializing," he said. With projections based on moderate and "our most hedonistic"
estimates of fossil fuel consumption, humans are the variable in the climate change equation.
The latest estimates by the International Panel on Climate Change (IPCC) predict a 2 to 11.5 degree Fahrenheit increase in global temperatures over the next century, based on low to high greenhouse gas emissions scenarios.
Under the high-emissions scenario, Dr. Thieler said that the three millimeter per year sea level rise estimate could "double or triple" in the next 100 years. Even if humans ceased to burn fossil fuels, sea level rise will continue, Dr. Thieler said.
Admitting that research is limited by elevation data that would establish a sea level baseline on Cape Cod, Dr. Thieler said that rising sea level has already resulted in noticeable changes to the coastline.
A National Water Level Observation Network tidal gauge based in Woods Hole shows that relative sea level has already risen by 10 to 12 inches over the last 100 years, he said.
Falmouth Heights eroded at a rate of 2.4 feet per year from 1975 to 1994, "a dramatic increase" that began after armoring projects became popular, Dr. Thieler said. The Green Pond shoreline used to be protected by a barrier island spit, he said, but after a revetment was placed there in the 1950s, the spit complex has retreated into the pond.
"In Falmouth, we’ve done a remarkable job of cutting off sand sources within the last century," he said.
Showing a picture of Falmouth Heights in 1845, he referred to a once-sandy bluff that is now held up by rock armor, saying, "one of these days, it’s going to let go. There’s not much holding it up."
Erosion on the east end of town is compounded by coastal engineering projects that impede the southeasterly flow of sediment from Nobska Point to Waquoit Bay, Dr. Thieler said. However, beach nourishment, such as the project at Menauhant Beach last winter, is not necessarily a solution.
That prognosis was shared by other panelists, who said costs and finding suitable sand will make it increasingly difficult to shore up the shoreline artificially.
Megan Higgins of the Rhode Island Sea Grant Legal Program said that beach nourishment "gives homeowners a false sense of security" and brings up legal issues over property rights.
"It’s not a long-term solution, even in tourist communities," she said.
However, Julia Knisel of the Massachusetts Office of Coastal Zone Management said that beach nourishment and dune building are "soft solutions" and are the "preferred alternative" to coastal engineering, provided that funding and a sand source are secured.
Tonna Marie-Rogers, coordinator of the coastal training program at the Waquoit Bay National Estuarine Research Reserve (WBNERR), asked the panel what they would recommend to town officials in order to deal with the issues on a local level.
Dr. Thieler, who served as chairman of the Coastal Resources Working Group (CRWG), commended Falmouth selectmen for establishing that committee, which made several recommendations for mitigating sea level rise in a report completed in May 2003.
In addition to facilitating the purchase of vulnerable coastal properties and removing physical structures like jetties and seawalls, the CRWG recommended relocating public roads and buildings inland from the coastline. Though the recommendations were established with the next 50 to 100 years in mind, Dr. Thieler said that the town does not have to wait to implement them.
"We’re not jogging. We’re still staggering forward," he said. The Menauhant Road bridge is an example of a structure that should be moved as soon as possible, he said.
Dr. Thieler also called for a full cost accounting of the "hidden costs"
of climate change, from flooding along Surf Drive to the costs of removing the sand that blows onto roads after a storm.
When the economic impacts of climate change are fully accounted for, he said, people will understand the true costs of their actions, or inactions.
Panelist Edouard Bard, of the College de France, summed up the moral imperative of scientists in researching and communicating the threats posed by climate change.
"The costs are too often the focus, when in fact we’re spared the costs with too-cheap fossil fuel," he said, pointing out that other countries pay much higher energy rates, or are faced with severe flooding. "Here we are speaking about cost, while in Bangladesh they are speaking about life."