Yale Environment 360 - Adam Markham*
The shores of Scotland's Orkney Islands are dotted with ruins that date to the Stone Age. But after enduring for millennia, these archaeological sites – along with many others from Easter Island to Jamestown – are facing an existential threat from climate change.
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Ruins on Scotland's Rousay Island coast, which is eroding because of sea level rise and intensifying storms.
ADAM MARKHAM
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Perched on the breathtaking Atlantic coast of Mainland, the largest
island in Scotland's Orkney archipelago, are the remains of the Stone
Age settlement of Skara Brae, dating back 5,000 years. Just feet from
the sea, Skara Brae is one of the best preserved Stone Age villages in
the world — a complex of ancient stone house foundations, walls, and
sunken corridors carved out of the dunes by the shore of the Bay of
Skaill. Fulmars and kittiwakes from the vast seabird colonies on
Orkney's high cliffs wheel above the coastal grassland of this rugged
island, 15 miles from the northern coast of the Scottish mainland. On a
sunny day, the surrounding bays and inlets take on a sparkling
aquamarine hue.
Older than the Egpyptian pyramids and Stonehenge, Skara Brae is part of a
UNESCO World Heritage site
that also includes two iconic circles of standing stones — the Ring of
Brodgar and the Stones of Stenness — and Maeshowe, an exquisitely
structured chambered tomb famous for its Viking graffiti and the way its
Stone Age architects aligned the entrance to catch the sun's rays at
the winter solstice. These sites, situated just a few miles from Skara
Brae, are part of an elaborate ceremonial landscape built by Orkney's
earliest farmers.
Skara Brae and the neighboring sites have weathered thousands of
years of Orkney's wild winters and ferocious storms, but they may not
outlive the changing climate of our modern era. As seas rise, storms
intensify, and wave heights in this part of the world increase, the
threat grows to Skara Brae, where land at each end of its protective sea
wall — erected in the 1920s — is being eaten away. Today, as a result
of climate change, Skara Brae is regarded by Historic Environment
Scotland, the government agency responsible for its preservation, as
among Scotland's
most vulnerable historic sites.
Like the rest of Scotland, Orkney's climate is changing faster now than at any time since instrumental measurements began.
A global crisis for cultural heritage is unfolding along our coasts,
but it's one that only a handful of archaeologists, preservationists,
and climate scientists are yet paying attention to. In 2014, for
example, a
study from
the Potsdam Institute for Climate Impact Research found 136 World
Heritage sites vulnerable to sea level rise, including the Statue of
Liberty and the Sydney Opera House. The
U.S. National Park Service has identified
erosion threats to archaeology at many of its properties, including Historic Jamestown in Virginia. Recent research shows that some of the magnificent
moai statues of Easter Island are
in danger of collapsing into the sea as a consequence of coastal erosion.
The threat is also severe in the Arctic, where protective winter sea
ice is disappearing and permafrost is thawing. Storms tear away the
shoreline and wash out irreplaceable remains of settlements, hunting
camps, and artifacts. Archaeologists are racing to excavate the
rapidly disappearing site of Walakpa near Barrow, Alaska, with its evidence spanning 4,000 years of human occupation.
Other coastal archaeology is critically endangered at Arctic sites in
Canada, Siberia, and Greenland. Resources to investigate and excavate
are meager.
Because of Orkney's weathered coast and the sheer density and
richness of its ancient remains, many see the archipelago as the world
capital of eroding archaeology. Hazel Moore, an archaeologist who has
been monitoring erosion impacts in Orkney and the even more northerly
Shetland Islands since the early 1990s, says, "In terms of coastal
erosion and direct threat, within Orkney and Shetland there are
thousands of sites at risk, and probably many we don't know about that
we're not even recording."
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Remains of the Stone Age settlement of Skara Brae in the Orkney Islands, threatened by sea level rise.
ADAM MARKHAM
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Moore leads one of Orkney's
several active "rescue digs" in
a fast-eroding dune system called the Links of Noltland on the island
of Westray, a 90-minute ferry ride from Mainland. Remains of at least 35
stone structures dating from 3300 BC to roughly 1000 BC have been found
there so far. In one of those, archaeologists discovered in 2009 the
Orkney Venus,
Scotland's earliest known representation of a human. Neolithic
settlement sites are rare, and the state of preservation at Noltland is
comparable to Skara Brae, although Noltland's area is considerably
larger. Each summer, the excavation team returns not knowing what
condition the site will be in after being battered by winter storms.
Like the rest of Scotland, Orkney's climate is changing faster now
than at any time since instrumental measurements began. Average
temperatures have risen by about 1.8 degrees F since 1961, and heavy
rainfall events and severe storms have become more common. Meanwhile,
sea level rise has accelerated during the last 20 years, driving an
increase in severe coastal flooding events on Scottish coasts, according
to Jim Hansom, a coastal geomorphologist at the University of Glasgow.
Until the 1980s Noltland's dunes were largely covered in grass, but
storms have hammered them, allowing wind erosion to take hold. (Sand
quarrying and rabbit damage also have taken a toll.) Intensifying winter
winds have scoured away sand and soil so that in some places the dunes
have collapsed nearly 20 feet. An ancient midden, or garbage pile, has
been exposed to the elements for the first time in thousands of years,
with shellfish and snail shells, fish bones, cereal grains, and charred
fragments of animal bones discarded by Bronze Age farmers lying directly
on the surface. Some of the most exposed portions of the site are no
more than 100 yards from the sea and just a few feet above beach level.
Moore says that speed of excavation is paramount because "nature is
uncovering the site so rapidly."
The evidence for human occupation in Orkney dates back at least 9,000
years, and although we think of the islands as remote today, for
several millennia they were a maritime and cultural crossroads, with
close links at various times to Ireland, Scandinavia, Greenland, and
mainland Europe. In the medieval period, Orkney was only two or three
days' sail by longboat from Norse harbors in Scandinavia.
Orkney's earliest inhabitants had to adapt to climate changes,
including post-glacial sea level rise. Seas around Orkney didn't reach
their current level
until about 4,000 years ago,
perhaps 500 years after Skara Brae was abandoned. It is likely that
encroaching sands and increasing salt-spray blown in from the sea
eventually made agriculture too difficult so close to the ocean.
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| Archeologist Julie Gibson on Rousay Island, which contains archeological finds dating back 5,600 years. ADAM MARKHAM |
By roughly 3,500 BC, must of Orkney's forests had been felled, and
stone, easily quarried from the islands' laminated red sandstone
deposits, became the building material of choice. Because stone was
used, the islands hold an extraordinarily rich repository of
archaeological information from the Neolithic period through to the
Vikings and beyond. At other archaeological sites in Europe, where wood
was used, the organic material has decayed and little is left of
buildings, but in Orkney, preservation of ancient structures is
remarkable, offering vivid insights into Neolithic life. For example,
the houses of Skara Brae contain stone beds, dressers, shelves, and fish
storage tanks.
"The buildings at Skara Brae indicated a pattern for how people
lived," said Julie Gibson, the Orkney County archaeologist and a
lecturer at the University of the Highlands and Islands. "When
archaeologists were digging near Stonehenge, they were dealing with
houses which had been built in wood, but to the same pattern as in
Orkney. They wouldn't have been able to so rapidly understand how people
lived near Stonehenge if they hadn't been able to draw on the 3-D
evidence from Skara Brae."
As at Skara Brae, most of Orkney's archaeological sites are on or
close to the shoreline, just a few feet above sea level. Accelerating
sea level rise is already having an impact, according to Gibson. Sixty
years ago, local children played inside beautifully preserved Iron Age
buildings at Hodgalee on Westray. Since then, seas that have risen five
to eight inches have entered and damaged these ancient remains. It's an
"archaeological disaster," says Gibson, and just a matter of time until
all are lost to the water and waves.
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| The medieval church of St. Mary's Kirk on Rousay Island, another example of Orkney coastal archeology at risk because of climate change. ADAM MARKHAM |
The 2013 Intergovernmental Panel on Climate Change
report
projected a range for global average sea level rise of 2.4 feet to 3.2
feet by 2100, but the latest science suggests that estimate is
conservative. The U.K. government has projected a possible rise in sea
level of
up to 6.2 feet by 2100.
On the Orkney Islands, huge waves roll in unimpeded from the deep
water of the Atlantic and batter the shore. Most studies show that storm
activity in the northern North Atlantic has intensified, and almost
all
climate change analyses agree that storm intensity will continue to increase.
Waves, too, are becoming more damaging. "In the Northeast Atlantic,
the significant wave height (the average of the highest third of all
waves) has been increasing over the last 40 years at about 0.8 inches
per year," says Hansom. But it's not the average waves that do the most
damage, it's the biggest ones.
Extreme waves up to 56 feet have been recorded off the west coast of Mainland.
Storms also appear to be clustering together more often, according to
Hansom. "The damage that storms do has a lot to do with the impacts of
the previous storm," he says. "If you have a beach that has been
depleted by a storm and then it's hit by another within a couple of
weeks, then the second storm is much more destructive." The 2017
National Coastal Change Assessment
found that Scotland's coastal erosion rates have doubled since the
1970s. All this could prove disastrous for Orkney's coastal archaeology.
An international team is
rushing to learn as much as it can about a newly discovered Stone Age
site before it is swallowed by the sea.
Exemplifying what's at risk is an extraordinary strip of archaeology
on the southwest coast of Rousay Island. Gibson has lived close by since
she moved here in the late 1970s to study Viking archaeology. In just a
few hundred yards you can hike the entire settled history of Orkney
from 3500 BC to the 20
th century, including one of the
biggest chambered tombs in Scotland, several Iron Age roundhouses
(brochs), remnants of a Norse hall, Viking boat ramps, and the ruins of
St. Mary's Kirk, once the heart of medieval Rousay.
Just down the beach from St. Mary's, an international team is rushing
to learn as much as it can about a newly discovered site at
Swandro Bay
— which includes a chambered tomb that may contain the burials of many
Stone Age people — before it is swallowed by the sea. The project also
seeks to better understand the mechanisms of erosion on coastal
archaeological resources. At Skara Brae too, cutting-edge efforts are
underway to record and understand the rate of erosion. A team from
Historic Environment Scotland used laser scanners for a
detailed 3D digital survey of Skara Brae and its shoreline.
Gibson looks at climate impacts both as a threat and an opportunity. She authored the 2008 book
, "Rising Tides Revisited: The Loss of Coastal Heritage in Orkney,"
in which she suggested that half the known sites in Orkney are at risk
from climate change. But she sees a silver lining: "This is an
opportunity for people to focus enquiries on eroding archaeology rather
than going to look for new sites."
She believes that some of these threatened coastal sites, if
protected and preserved, can provide not only invaluable knowledge about
the past, but also help drive economic development on Orkney by
bringing more visitors to the outer islands.
Both Gibson and Moore hope that some of the important archaeological
sites now at risk of loss on the coasts can be protected for several
generations at least. This may require new sea walls, breakwaters, or
dune restoration in some places. What's most needed, says Gibson, are
the political will and financial resources to both excavate and
stabilize Orkney's archaeological treasures.
On a sunny day, standing by the sea and looking over the remains of
the ancient houses at Skara Brae, one feels an affinity with the people
who lived there 5,000 years ago. But the waves rolling onto the beach
are a reminder that time is ticking for this extraordinary place and for
so many other sites on Orkney's coastline.
*Adam Markham
is deputy director for Climate & Energy at the Union of Concerned
Scientists (UCS) in Cambridge, Massachusetts. He writes about climate
impacts on biodiversity, conservation and cultural resources, and on
international climate policy. He was lead author of the 2016
UNESCO/UNEP/UCS report "World Heritage and Tourism in a Changing Climate."
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