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The CHERISH Project (standing for Climate, Heritage and Environments of Reefs, Islands, and Headlands) began in January 2017 and ended in June 2023. Prior to the awarding of the grant, it took the best part of two years to prepare the application and to think hard about how best to understand the past, present, and near-future impacts of climate change on coastal heritage.
Defining climate change
Compiling an application involved first establishing an understanding of what we meant by ‘climate change’. The popular image is of global warming leading to the melting of ice caps and glaciers, and in turn resulting in higher sea levels that either inundate low-lying lands or erode the coast. All of this is happening, but we soon realised that there were many other aspects to climate change that are equally damaging to the historic environment: invasive vegetation with roots that can damage archaeological deposits; the drying up of the bogs that are a source of knowledge about past environments, and of waterlogged deposits that preserve organic materials; the acidification of soil that destroys organic remains; and the movement of sand that exposes hidden archaeology and makes it vulnerable to further erosion.
Most of all, the more frequent occurrence of extreme weather, characterised by intense rainfall (25mm to 50mm an hour), can wash archaeological remains into the sea through a combination of sub-surface water and the fast-flowing floodwaters. This is worsened by periods of intense drought that desiccate the fragile coastal soils, leading to wind erosion and the creation of cracks that become rainwater gullies. Coastal archaeology is thus being eroded from both sides – from the land and from the sea – and even the relatively solid slate and mudstone geology of some parts of the Irish Sea coast is experiencing regular landslides and cliff-face collapse.
Understanding the differential impacts of climate change on various kinds of geology and soil meant that CHERISH was designed from the start as a multidisciplinary project. In addition to our archaeological counterpart, the Discovery Programme Ireland, our partners were the Geological Survey Ireland and the Department of Geography and Earth Sciences at Aberystwyth University. We learned much from all our partners, but especially from the geologists and geomorphologists – to the extent that we would now recommend the inclusion of such specialists in any archaeological project. Their insights into the environmental opportunities and constraints faced by our predecessors were illuminating, as is their ability to help us distinguish between natural features and processes and those resulting from human action.
Choosing the case studies
We had to make decisions, too, about which coastal locations to examine out of the combined total of some 5,000km (3,100 miles) of coastline in the study area. As well as sites at the edge of the coast, we needed to include archaeology in the intertidal zone and beneath the sea in inshore waters (under 40m/130ft in depth). Within these three zones, we selected a diverse range of sites and landscapes, including promontory forts, castles and monasteries, shipwrecks, exposed peat and submerged forests, coastal lakes and lagoons, wetlands, dunescapes, and offshore islands.
These study areas were chosen with the help of numerous agencies, landowners, and local groups, based on current and future climate-change risks. As a result of our work, these partners now have a better understanding of the processes of change that will feed into future site-management and enable continuous monitoring well beyond the end of our project.
One of the areas selected for study in Wales was the Dinas Dinlle hillfort, in Gwynedd, owned by the National Trust. It is set on a hill that stands high above the otherwise level Caernarfonshire coastal plain (so flat that there is a small airport just to the north). As well as being a Scheduled Monument, the hill is a Site of Special Scientific Interest, designated for the importance of the glacial till, sand, and gravel sediments clearly exposed in the cliff face. These were laid down at the end of the last Ice Age, around 12,000 years ago, and fresh deposits are exposed every year by cliff falls which have eroded the western defences of the hillfort. Over the last 100 years, the site has lost an average of 0.4m (15in) a year, and at this rate the entire site will be gone within 500 years.
Features exposed by recent collapses were recorded at Dinas Dinlle and at other sites, including Caerfai Promontory Fort in Pembrokeshire and Ferriter’s Castle in Co. Kerry. This required new techniques and a head for heights. Excavation and recording work were supervised by an experienced rope-rescue technician and members of the CHERISH team undertook rope-access training.
Having acquired these new skills, an extensive cliff-face survey was carried out at Woodstown Promontory Fort, near Annestown, Co. Waterford. This is one of 32 such forts found along a 22km (14 mile) stretch of rapidly eroding coast where copper and other mineral deposits were mined in the18th and 19th centuries. A cliff-face collapse in 2021 led to a three-day excavation using ropes and harnesses, and though UAV (Uncrewed Aerial Vehicle, or drone) survey was also undertaken, human inspection, recording, sampling, and artefact recovery proved to be critical for an understanding of the exposed archaeology. Flints, a grinding stone, and a sling shot were recovered, and soil samples (yet to be analysed) were taken in order to look for evidence of prehistoric metal- working within the fort.
Back at Dinas Dinlle, we worked with Gwynedd Archaeological Trust (now part of Heneb: the Trust for Welsh Archaeology), SUMO Geophysics, and Birkbeck University on more conventional geophysical survey techniques (magnetometry, resistivity, and ground-penetrating radar) to build up a picture of the sub-surface archaeology at Dinas Dinlle. This revealed just how crowded the interior was with roundhouses and linear features.
Again with Gwynedd Archaeological Trust, and aided by an army of volunteers, we excavated a section of the most-threatened archaeology along the edge of the eroding cliff face in order to date and phase the site. From this we discovered that the hillfort builders had made good use of natural periglacial features to construct their defences, steepening the pre-existing slopes and accentuating their ramparts.
The archaeology within the hillfort was found to be buried under c.2m (6.5ft) of sand, demonstrating that high winds and shifting beaches are not just a modern phenomenon. Optical stimulated luminescence dating enabled us to show that wind-blown sand started accumulating here from the Middle Iron Age onwards (around 250 BC), and was an ever-present challenge to the occupants of the hillfort. Sand had pretty well covered the entire site by AD 1100, and later generations took advantage of these deposits to create the bunkers of a golf course on the hilltop, which opened in 1906. Among the ‘small finds’ from this period in the site’s use was a vintage gutta-percha golf ball, made from the rubber-like sap of the sapodilla tree; collectors of rare golf memorabilia approached us online with offers to buy the golf ball when we revealed the find.
Golf balls aside, the star find from the excavation was a massive late prehistoric roundhouse, measuring 13m (43ft) in diameter with 2.5m (8ft) thick walls. David Hopewell, senior archaeologist at the dig, described this as ‘the biggest one I’ve ever seen in 30 years of archaeology’ (see CA 356 and CA 403).
To study the fort’s hinterland, the CHERISH team extracted cores from nearby wetlands and from the peat deposits exposed at low tide on the foreshore, both of which provided evidence for the evolution of the landscape and the vegetation history. This showed that around 7,500 years ago, in the Mesolithic period, woodland stood where the beach is today and sea-levels were around 5m lower than they are now. In the later prehistoric period, there was a tidal inlet where the fields and village of Llandwrog are found today, the perfect location for a sheltered harbour (visit the CHERISH website at https://cherishproject.eu/en/ for an animation showing the development of Dinas Dinlle over time).
Surveys, surveys, surveys
As well as excavating sites in advance of their loss, the CHERISH Project team undertook a number of baseline surveys using LiDAR, satellite, and UAV at sites that will be monitored regularly for many years to come. The team carried out a UAV survey of a motte-and-bailey castle on a promontory that is being eroded at Glascarrig, in Co. Wexford, which was probably built by William de Caunteton in the late 12th century and surrounded by a settlement of some 48 burgage plots, which were later abandoned. The motte and surrounding landscape were subjected to a UAV survey three times between June 2018 and June 2021, and this provided the data for digital ‘deviation maps’, which use different colours to indicate significant areas of erosion. Fortunately, none was detected at the castle, but the approach is one that can be used in the future to reveal changes at the project’s monitoring sites.
The second year of the CHERISH Project coincided with one of the most severe droughts in recent years, with some of the warmest, driest, and sunniest days on record between April and July 2018. Soil Moisture Deficit readings provided by the Met Office were used to predict when agricultural crops were likely to be under the kind of stress that encourages cropmarks to form, and a programme of aerial photography resulted in the discovery of 100-plus new sites in Wales.
CHERISH also commissioned airborne laser-scanning (LiDAR) surveys for six islands in Wales. The 0.25cm resolution data, a first for these islands, offered unparallelled new views of the landscapes and provided new data from which to map the rich archaeology. This technique had a particularly significant impact on Puffin Island, where dense vegetation obscures the archaeology around the island’s former monastic settlement. The digital terrain model (DTM) created from the data, effectively ‘stripped away’ the vegetation to offer a bare-earth view of the island landscape for the first time in decades.
We now know more about the settlement and farming history of two islands off the coast of Pembrokeshire – Grassholm and Skomer – previously known for their rich birdlife (including thousands of gannet nests and puffin burrows). The CHERISH team from Aberystwyth University Luminescence Research Laboratory successfully used OSL dating on one of Skomer’s field lynchets to provide the first scientifically dated evidence for Middle Bronze Age, Middle Iron Age, and medieval clearance and farming on Skomer. The medieval date radically alters our understanding of Skomer’s archaeology, since it had previously been thought that the island had largely been abandoned, save for seasonal grazing and rabbit-farming, during this period.
Re-examining Wrecks
These islands and coast are also notorious for shipwrecks, and the CHERISH team researched one particular intertidal wreck named The Albion. This wooden paddle steamer was built at Bristol in 1831 by the General S P Company to transport people and goods between Bristol and Dublin. In 1837, the ship’s captain was forced to change course to avoid running down a rowing boat with four men on board. The change of direction and the force of the tide caused The Albion to strike a rock, and the ship ran aground at Albion Sands to the south-west of the Marloes peninsula in Pembrokeshire. Following a baseline survey, the wreck is now being monitored regularly by the Royal Commission to analyse the ways in which storm events influence sand movement in the exposure and inundation of the wreck. One result has been the creation of an information panel about the wreck and the impacts of climate change now on display in a nearby National Trust car park.
Maritime archaeology was another key component of the project, seeking to understand how changing seas – and the lifeforms they support – might be affecting listed wrecks. Wales has six protected wrecks (one of which is a prototype submarine) and we selected one of these for study because it lies in relatively accessible and shallow waters, and because a measured survey had been carried out in 2004 by Wessex Archaeology, presenting an opportunity to see what had happened to the site since then.
The site probably represents the remains of a Genoese merchant vessel lost in 1709 while carrying a cargo including a substantial quantity of marble blocks from the Carrara quarries in Tuscany, which form a low mound on the seabed surrounded by a scatter of cast- and wrought-iron guns and anchors. Officially known as the Tal-y-Bont Wreck, it is familiarly known as the Bronze Bell Wreck after the discovery of a bronze bell, dated 1677 and bearing the legend Laudate dominus omnes gente (‘Praise the Lord, all ye nations’), during an early exploratory dive.
The CHERISH team commissioned MSDS Marine to visit the site to see what impact there might have been from the seabed turbidity resulting from stronger and more frequent storms. Several divers who had visited the wreck in the past joined the project to share their experiences, including Geraint Jones, who was a member of the original team that found the site in 1978. In particular, he noted the change in marine species revealed by the audit of fish, crustacea, molluscs, algae, and seaweeds seen at the site as a result of ocean warming. Seawater samples were collected, too, to provide baseline data for monitoring acidification in years to come, and ominous signs of plastic pollution were recorded at the site.
The public was kept informed by means of an onshore information caravan located at Pwllheli showing video footage of the survey work in progress. This attracted a huge amount of interest, and when a visitor commented that the team looked like busy bees in their distinctive yellow and black T-shirts, the caravan was dubbed ‘the Heritage Hive’.
Such was the public interest in this work that a team from Channel 4 News turned up to interview members of the team and find out more about the CHERISH Project (the five-minute report, which was broadcast on 22 September 2021, can be seen on YouTube: http://www.youtube.com/watch?v=x1HgNtVKEss). A group of enthusiastic children from a local primary school (Ysgol Gynradd Abererch) also arrived to ask questions, try on diving equipment, and make Bronze-Bell-inspired badges as part of their term’s work on local shipwrecks.
Under the sea
Another approach to marine survey was deployed during the project in the form of various types of acoustic mapping. Echosounding equipment can be used to map seabed geology and sediment density, depending on the sound frequencies used, and even to measure water velocity and direction at different depths within a water column. Survey vessels working for the INFOMAR programme, which is mapping the entirety of the seabed in Irish waters, were engaged by the CHERISH Project to study specific wrecks, including the Manchester Merchant, which caught fire in Dingle Bay, County Kerry, in January 1903 on the way to Manchester from New Orleans. Her cargo of 13,000 bales of cotton, as well as 100 barrels of turpentine, soap, pitch pine, and maize, helped fuel the blaze so, as a last resort, the captain scuttled the ship. The CHERISH survey recovered a highly accurate and detailed image of the intact ship and the remains of its cargo, revealing that the bow and stern were the areas most vulnerable to the currents that are undermining these parts of the vessel, and that the boilers at the centre of the wreck are breaking down as well, in response to wave and storm action.
Similar techniques were used to survey the Bronze Bell Wreck and another wreck – discovered as recently as the summer of 2000 – which was initially identified as the Diamond, and designated in April 2002 as the oldest known example of an American composite-built hull, constructed of oak on an iron frame. Built in New York in 1823, the Diamond was owned by Josiah Macy, a nephew of Rowland Macy, founder of Macy’s department store in New York. The ship was designed to make regular fast passages across the Atlantic. In the early hours of 2 January 1825, in the mistaken belief that the vessel was far enough north to turn east for Liverpool, the vessel sailed into the northern end of Cardigan Bay and struck the side of Sarn Padrig, a shallow sand and gravel bank that extends over 19km (12 miles) out from the Gwynedd Coast.
Prior to the CHERISH Project, there was no detailed bathymetric survey of the reef to provide an understanding of the context of the wrecks and the dynamics of the surrounding seas. It is now known that Sarn Padrig is a drowned esker, a narrow sinuous ridge, some 80m (262ft) in width, 8m (26ft) in height, and lying only 6m to 11m (20ft to 36ft) below the surface, formed by a sluggish river within a glacier depositing sediment over an extended period. The reef continues to be a major cause of grounding, and the data recorded by the CHERISH Project has been submitted to the UK Hydrographic Office to be used to update charts and for navigation safety.
Despite all this sophisticated technology, good old-fashioned field walking played a key part in the Project. One example was the coastal zone assessment carried out around the 10km (6 mile) stretch of mud and sand flats around the Rogerstown estuary north of Dublin, an area classified as being under a high level of threat from sea-level rise. Beginning with a desk-based assessment to identify archaeological features from aerial photographs, maps, and charts, the field survey stage found 34 sites, of which 16 were previously known but not fully recorded. They included stone-lined graves emerging from a cliff face, worked flints, shell middens, jetties and landing places, and sites associated with copper-mining. All exhibited signs of erosion, from ‘slight’ to ‘severe’, classifications that will be used to establish priorities for further survey.
In conclusion, the main achievement of the CHERISH Project was to test a variety of different approaches to the monitoring of climate-change impacts on the historic environment. The results have been published in the form of a CHERISH Toolkit (see ‘Further reading’ box below), assessing the value of each approach under a range of criteria: the type, size, and extent of site for which the approach is most suitable; the cost; the level of skill required; the outputs; the significance of the site; and the severity of the threat.
This generously funded six-and- a-half-year project has proved to be a rare and valuable opportunity to undertake some in-depth research, but in the longue durée of climate change it is but the blink of an eye. The future value of all this work will come from continued monitoring of vulnerable sites using the baseline data acquired during the course of the project, and designing ways to mitigate the impact or to carry out further excavation work at sites most at risk of complete destruction.
Further reading: CHERISH – Sharing our Practice: Investigating Heritage and Climate Change in Coastal and Maritime Environments (ISBN 978-1871184624) is available as a free download in English and in Welsh from the Royal Commission’s website (https://shop.rcahmw.gov.uk).
ALL IMAGES: CHERISH Project, unless otherwise stated
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