Rising Seas Threaten to Swallow These Ten Global Wonders

Climate change-induced increases in sea level are forcing archaeologists and communities to get creative and make tough calls

Reproduction of early English vessels at Jamestown, Virginia. NOAA

Not all of the world's treasures are kept in museums. Cultural heritage sites—historic cities, monuments and archaeological sites—inspire awe and show the best of humanity throughout time.

Yet cultural heritage sites around the world face a host of impending threats, and perhaps none seems more inevitable than rising seas fueled by melting ice caps. “It’s one of the most dramatic effects of climate change,” says May Cassar, a professor of sustainable heritage at University College London.

While the drama of submerged landmarks piques the artistic imagination, it’s a harsh reality that both scientists and local communities will soon have to cope with. Current projections suggest that by 2100, sea levels may rise by six feet on average. Earlier this summer, researchers reported that sea-level rise is speeding up, and according to estimates released this month, burning off Earth’s remaining fossil fuels would completely melt the Antarctic ice sheet and raise sea levels by 190 feet.

If things continue unchanged, many coastal sites of historical and cultural significance will be underwater. “We have to deal with that knowledge and make some prioritizations,” says Adam Markham of the Union of Concerned Scientists. International organizations like the United Nations Educational, Scientific and Cultural Organization (UNESCO) compile lists of important sites, but determining what’s at most risk and what’s worth saving is no easy task.

Last year, climate scientists Anders Levermann and Ben Marzeion modeled how sea-level rise might play out at 720 UNESCO World Heritage sites. If global temperatures rise only moderately—by three degrees Celsius—over the next 2,000 years, their models suggest that 136 of these sites could be underwater, including the Tower of London and the Sydney opera house. However, predicting this worst-case scenario in the short term is a bit of a crapshoot.

Further complicating matters, sea-level rise can have other unintended impacts. Flood levels and frequencies may increase, and storm surges might be higher. That’s a problem because "a single storm can completely destroy a site," explains Tom Dawson, an archaeologist at St. Andrews University in Scotland.

Still, storms can also have beneficial effects. "What’s more likely is that a storm will do some damage but actually expose something in the process,” Dawson says. On Scotland's coasts, storms have revealed ancient dwellings and even skeletons of past inhabitants.

Coastal erosion is a more chronic issue that rising seas could exacerbate. “It’s not new, but it has gotten a lot worse. We’re kind of powerless against it,” says Torben Rick, an archaeologist at the National Museum of Natural History. Most coastal archaeological sites aren’t famous or flashy but contain evidence of how people lived thousands of years ago. “With every bit that erodes away, we’re losing a piece of cultural heritage,” says Rick.

On the plus side, the impending demise of some sites has spurred new levels of creativity in efforts to preserve and record them—though photographs, excavations, ground-penetrating radar and land and aerial surveys. A startup called CyArk aims to create 3D digital blueprints of 500 heritage sites using lasers in the next five years.

Successful efforts will depend on local communities. “The focus is typically on the monument. But the focus also needs to be on the people that surround that monument,” says Cassar. Sea levels may displace a lot of coastal communities, but helping them survive and preserve heritage extends the life of those sites as well.

Ultimately, communities will have to make tough decisions about whether to try to preserve, move or abandon these areas. Here are ten sites that could face a watery fate:

Jamestown, Virginia

The first permanent English settlement in the Americas sits right about at sea level in the Tidewater region of Virginia—an iconic trove of U.S. history. Over the years, Jamestown has yielded countless artifacts from pottery to weaponry. In 2013, archaeologists turned up the remains of a young girl who had been cannibalized by starving colonists in 1609. Most recently, researchers unearthed skeletons belonging to four of the colony’s prominent leaders.

At the time of settlement, Jamestown would have been situated much further inland than the beachfront on which it sits today. While erosion from flooding and storm surges eat away at the shoreline, the land itself is sinking. One corner of the original fort has already been lost to the elements. Waters that encroach on the site do so at roughly twice the global rate, and by some estimates, water level could reach six feet by the end of this century.

Archaeologists have already excavated most of the original fort in anticipation that the site’s bounty might slip beneath the sea. The National Park Service also put in an underwater wall of rocks to help break waves before they hit the shore, reducing erosion. There’s discussion of building a seawall as well.

Skara Brae, Scotland

Perched on an eroding bluff on the Scottish island of Orkney, the Neolithic site called Skara Brae includes eight stone-walled houses built into the ground. Humans occupied the site from 3100 B.C. to 2500 B.C., and it's one of four sites flagged by UNESCO in the region as being of “outstanding universal value.”

A seawall protects Skara Brae from swells, but it’s taken a beating over the years, and rising tides may overcome the barrier. By the time global temperatures rise by more than 1.8 degrees Celsius, parts of those sites may be submerged. But the more immediate threat is coastal erosion. Archaeologists have worked to extensively excavate and document the site. Back in 2010, CyArk scanned Skara Brae along with other Neolithic sites in the region.

The larger issue is that Skara Brae is just one of thousands of archaeological sites along Scotland’s coast—and many more may await discovery. That’s why Tom Dawson, the St. Andrews archaeologist, and his colleagues started SCHARP, short for Scotland’s Coastal Heritage At Risk Project. The program enlists help from local communities in recording and documenting new sites revealed by changes in vegetation, storms and erosion through a smartphone app. They’ve recorded 11,000 sites so far. Recently, the citizen science project also helped scan and 4D model the Wemyss Caves, a series of seaside caves adorned with Pictish petroglyphs carved between 400 to 600 B.C.

Kilwa Kisiwani, Tanzania

Off Tanzania’s coast lies a small island called Kilwa Kisiwani, once a thriving seaport and political center. Occupied since 200 B.C., the island became a port for the mainland gold trade in the Middle Ages. An ancient drop in sea level may have actually helped facilitate the island’s settlement and rise to power.

Today, the island’s ruins include a palace and a huge mosque—one of the largest in sub-Saharan Africa—from the 14th century, as well as a Portuguese fort. Songo Mnara, an ancient village, sits on a neighboring island. Together the two sites have been listed as a UNESCO heritage site since 1981.

Some buildings stand flush with the sea, so coastal erosion is a constant issue. Protective mangrove forests suffered serious deterioration in the last century. In 2008, a heritage conservation group called the World Monuments Fund (WMF) teamed up with local communities to replant trees, restore walls and rebuild structures that had collapsed. A big part of their work involved training locals in conservation techniques. For now, the site is out of immediate danger, but an uptick of 2.8 degrees Celsius would put it below average sea level, according to Marzeion and Levermann.

Herschel Island, Canada

The Thule culture first inhabited Herschel Island (called Qikiqtaruk in Inuit) a millennium ago. In the 19th century, European whalers arrived and began using the island as a trading center. Eventually Thule Inuit tribes moved inland, and the whaling market began to fail. The island is home to native and colonial sites of historic value, but aside from a few scientific researchers, it remains unoccupied today.

Like any coastal locale, erosion has proved a chronic source of stress for Herschel Island’s survival, and rising sea levels will only worsen the receeding coasts. In addition, with less sea ice in the region, more cruise lines are able to make their way further north, exacerbating erosion on coastlines, notes Cassar. “It’s never just one thing,” she says.

Currently, there are no large-scale efforts to stem the effects of sea level rise around the island. 

Venice, Italy

Founded around A.D. 600, Venice spreads over 118 lagoon islands connected by canals, and the city contains numerous monuments to art, architecture and cultural history.

High tides have long plagued the "bride of the sea." Floods hit the city seasonally, but current sea-level rise is likely exacerbating the issue. “As sea level rises, buildings in Venice flood more and more often—to the point where any high tide causes flooding,” says Markham. With a temperature increase of just 0.7 degrees Celsius, at least part of Venice will soon sit below local average sea level, Marzeion and Levermann calculate. The fact that the city is sinking by about two to four millimeters each year (and tilting slightly east) will only make matters worse.

To combat the problem, the city has constructed a series of elaborate sea walls and floodgates. However, by some estimates, the expensive defenses may not be enough to protect the city from rising tides.

Elephanta Caves, India

Located on Gharapuri Island in the Sea of Oman, just off the coast of Mumbai, the rock art of Elephanta Caves dates back to A.D. 500. Archaeological evidence suggests that humans settled the island even earlier, around 200 B.C. The rock art decorates temples carved into some of the island’s hills and is linked to the Cult of Shiva sect of Hinduism.

Marzeion and Levermann project that a temperature rise just under one degree Celsius could put parts of the island underwater. The Archaeological Survey of India has seven ongoing excavations at the site.

Robben Island, South Africa

The Khoikhoi people of South Africa were the first inhabitants of Robben Island. Over the years, the island has served as the site of a prison, a military base, a whaling station, a hospital and a leper colony. The famed locale of Nelson Mandela’s incarceration became a UNESCO site in 2011. Buildings remain from the island’s 19th- and 20th-century settlements, and the site remains an iconic symbol of South Africa’s struggle to end apartheid.

Conservationists have made an effort to digitally preserve the site’s history by documenting prisoners’ personal experiences and maintaining extensive photographic, audio and textual archives. Still, Robben Island’s location alone puts it at risk. The flat island is actually the summit of an underwater mountain once connected to the mainland. It sits only a few feet above sea level. By Marzeion and Levermann’s 2014 estimates, part of Robben Island could be underwater with the tiniest of global temperature increases—a mere 0.2 degrees Celsius.

Nessebar, Bulgaria

A popular tourist spot, Nessebar sits on a Bulgarian peninsula that juts into the Black Sea. Built 3,000 years ago by Thracians, the ancient city has since been home to a variety of cultures. It became a Greek colony around 700 B.C., fell to Roman rule around 71 B.C. and eventually served as stronghold for Byzantine and Ottoman empires during the Middle Ages. Nessebar’s sheer variety of ancient cultural architecture put it on UNESCO’s list.

However, rising seas have already reduced the city’s land by about a third, and it’s living on the edge. The city sits between zero and 59 feet above sea level, and an uptick of 0.9 degrees Celsius could put part of the city below sea level. Several preservation projects aimed at specific city sites are currently underway. 

Sonargaon-Panam City, Bangladesh

Settled by traders in the 1200s, Sonargaon once served as a center of trade and politics in East Asia. Bengal ruler Isa Khan named it his capitol in the 1400s, and its architecture spans from the Mughal Empire through British colonial rule.

Today, the area known as Panam City lies empty outside Bangladesh’s capital, Dhaka. In 2008, the World Monuments Fund put the city on its 100 most endangered sites list, and Bangladesh’s national archaeology department is in the process of trying to excavate and preserve notable city landmarks.

Floods that routinely threaten the area could get worse with rising seas. But the bigger problem may be a gradual influx of people migrating to the coast for better economic prospects and squatting in the historic buildings, most of which were abandoned in the 1960s. “The city fabric is actually deteriorating quite dramatically,” says Cassar. 

Turtle Mound, Florida

It might not look like much, but Turtle Mound is a shell midden (basically an ancient trash heap of oysters, fish bones and clams) left behind by the Timucuan people who inhabited Florida’s shores around 1,200 years ago—long before Europeans arrived. At 35 to 50 feet tall, it’s one of the largest shell middens in North America.

By 2100, sea level is expected to rise 26.4 centimeters at Turtle Mound—combined with hurricanes and other storm surges, that will likely exacerbate coastal erosion at the site. To protect the mound, the National Park Service and the University of Central Florida constructed a living shoreline of oysters, grasses and mangrove trees to buffer the onslaught of waves.

Turtle Mound is one of a larger body of shell midden sites that line coasts around the globe—all at risk of being swallowed or eroded by rising seas. Many are thousands of years old and hold clues to how ancient cultures coped with life along the coast.

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