By February 2021, over three-quarters of the District, County, and Metropolitan councils in the UK had declared a Climate Emergency, publicly stating their aim of working to achieve a carbon-neutral stance within the next 10-30 years. This came in response to the alarming increase in global warming exacerbated by such issues as the burning of fossil fuels. The impact of such worldwide changes in temperature can be seen in abnormally cold and warm winters, together with hotter summers and the attendant increase in wildfires, droughts, and dust storms, as well as an increase in events when what was once seen as a month’s-worth of rain falls in a few hours (with the consequential fluvial flooding). These extreme storms, together with relative sea-level rises, cause increased coastal erosion, and, even if greenhouse gas emissions are restrained, by the end of this century the global mean sea-level is still likely to rise at least 0.3m above what it was in the year 2000. This is due to a combination of increasing meltwater from glaciers and ice sheets with the thermal expansion of seawater as it warms. Indeed, the 2021 IPCC report warns that coastal areas will see more severe coastal flooding and coastal erosion, while extreme sea-level events that previously occurred once every 100 years could become the new annual normal by the end of this century.
Such a situation has dire consequences for low-lying islands and estuaries in the Pacific and Indian Oceans, as well as for all waterfront settlements lacking appropriate flood defences. In the UK, coastal settlements have an additional burden to bear, but are already among the most deprived towns in the UK. (Coastal settlements have an income output per capita 26% lower than non-coastal communities.) We can no longer stop sea-levels rising, but we must try to be better prepared to address these serious national challenges.
This is also a concern for the team at CITiZAN (Coastal & Intertidal Zone Archaeological Network), a community-based archaeological project supported by the National Lottery Heritage Fund and managed by MOLA (Museum of London Archaeology). Developed in 2015 from the successful Thames Discovery Programme in London, CITiZAN is working to record over 6,000 miles of archaeology along England’s coasts that is at threat from weather, waves, and human action. Documented sites range from prehistoric forests and Roman saltworks to the lost medieval port of Dunwich in Suffolk and numerous shipwrecks (see CA 306; CA 324 features CITiZAN’s work recording specifically First World War-related features, including pillboxes, sound mirrors, and the remains of both British and German submarines). The project has gone on to establish new Discovery Programmes in Liverpool Bay, Humberside, Essex, Kent, and the Solent. Our particular climate emergency is that accelerating erosion is attacking our coastal heritage. We are surveying archaeological features exposed on the open foreshore that are being destroyed by every tide, preserving them not with sandbags, but by record.
Systematic survey of those sites at risk does more than just provide a permanent archive of our island nation’s fragile and neglected heritage, however. The database being compiled can actually contribute not just to a better understanding of the current situation, but can facilitate evidence-based estimates of the rate and extent of tomorrow’s coastal change. In other words, we can learn lessons from the past to better inform the future. That intertidal zone survey can contribute to studies of coastal erosion is clear: monitoring the rate at which archaeological features on the open foreshore are exposed then destroyed by natural agencies is already seen as a proxy for an increasing rate of tidal scour. As layers of soft waterlain sediments are stripped off the foreshore, sealed archaeological horizons that had previously been hidden from view for millennia are suddenly revealed. Again, the exposure and study of features such as extensive tracts of prehistoric ‘submerged forest’ provide clear evidence of the level of what was once dry land, and for the date at which this landscape was inundated by rising sea-levels in an earlier epoch. Previous generations faced similar risks to those that we are facing today. They too had to endure glacial advances, as well as the subsequent global warming: the key to survival then, as it is now, was adaptation.
CHANGING MINDS, CHANGING COASTS
In the early 1990s, the Government in England and Wales established Shoreline Management Plans to enable longer-term planning of risks to people and the environment from coastal flooding and erosion. These plans were designed to identify sustainable approaches to future challenges over the next century, in the short term (the next 20 years), medium term (20-50 years), and long term (50-100 years). CITiZAN’s more recent project, ‘Changing Minds, Changing Coasts’ (CMCC), which is funded by the Natural Environment Research Council, took a different approach, however. Instead of looking to the future, the team reworked that concept from an eco-archaeological perspective, initially looking at the rates of coastal change over the previous 100 years on Mersea Island, just south of Colchester in Essex, on England’s very vulnerable east coast.
Climate change wasn’t the only challenge for the CMCC project. NERC’s grant was also focused on how to conduct meaningful environmental research with communities under COVID-19 lockdown conditions. During these restrictions, we had no physical access to sites and no face-to-face communication with participants, and so a new methodology to accurately map how and why these changes took place was required. Using a series of indicators relevant to the Mersea foreshore (the range of biodiversity, extent of saltmarsh cover, presence and absence of seagrasses, among others), a framework for data collection was established. Because coastal communities are first-hand witnesses to the scale, speed, and nuances of changes in these indicators, the team also sought to capture and categorise the memories and image archives of a small team of local volunteers. Established members of the community with long and strong ties to the island were interviewed, documenting memories spanning a period of 60 years or more, and providing nearly five hours of oral histories. These were explored through discussions prompted by more than 300 postcards and photographs spanning the last century – this evocative collection had been brought together from members of the community via a call on social media platforms, and from the Mersea Island Museum’s extensive archive.
For this pilot study, we selected two sites at opposite ends of Mersea Island’s four-mile length: one at Monkey Beach (West Mersea), the other at Cudmore Grove (East Mersea). Both are known for their popularity among locals and tourists over the last century and for their vulnerability to coastal erosion. Additionally, the CITiZAN team had already completed high-precision surveys of an impressive range of exposed archaeological features on these sites, all now with absolute levels, providing valuable archaeological context for this co-created data set. Historic Ordnance Survey data provided the background maps on to which this unique information would be projected, plotting the accelerating rate of changes to the shoreline and foreshore in 20-year intervals spanning 1920 to 2020. Each interval map combined memories and images in an attempt to recreate a snapshot of the state of the foreshore, noting the presence/absence of a range of archaeological and environmental features. These included the height of contemporary high-water and low-water marks; the extent of salt-marsh and evidence of, for example, eel grass, seaweed, and fish; the condition of foreshore (for example, rills, sand, shingle, and silts), as well as cultural use (for example, fishing, oyster-farming, military, recreation).
The potential value of this uniquely detailed, community-constructed eco-archaeological data set is considerable. It provides a vivid timeline of change, from a landscape to individual organism resolution, against which the impact of human interactions with the environment can be measured. For example, the effects of technological changes driven by social needs, such as with intensified agricultural practices, can be measured not just in terms of those people who relied upon it, but the unanticipated effects on the environment.
MAPPING A CENTURY OF COASTAL CHANGE
The CMCC study revealed a story of significant change, with clear tipping points throughout the last century that transformed Mersea’s foreshore. As part of the wider public engagement work, the study has been reworked as a digital Storymap supported by an exhibition in the Mersea Island Museum. The full report will be made available on the CITiZAN website, but we can summarise our findings in the following timeline.
In 1920, Mersea Island looked very different to how it does today. Vast, richly biodiverse marshlands covered the foreshore to the south of the island, and these were crossed by a network of creeks navigable by Thames barges, while Hove Creek in the west was accessible to fishing boats. Mudbanks at the low-water line supported seagrasses like eel grass (Zostera marina) and a wide variety of shellfish – a key feature, as sea grass meadows play a vital role in reducing the impact of coastal erosion. Their roots and the waste products of molluscs living within these environments bind silts into stable banks, while their grassy fronds dissipate wave energy, reducing foreshore damage. By the 1930s, though, this landscape was beginning to change, as a wasting disease attacked the eel grass meadows.
The drive to produce more food in the period after the Second World War resulted in an increased use of fertilisers on farmland. But the chemical run-off (particularly nitrogen) from those fields polluted the estuary, destroying the last of the eel grass meadows. As the grasses died, the mudbanks became unstable and waves began to break them up, in turn exposing the foreshore to erosion. By the 1950s, the creeks had become silted up and unnavigable, while the flat grassy meadows were lost. Mud hillocks, increasingly separated by rills, now typified the landscape, but still supported some shellfish and seaweeds. Shingle displaced by erosion began accumulating to the western end of Monkey Beach as a large spit began to form, while increased sedimentation restricted access for fishing boats in Hove Creek. As tidal scour accelerated, timber structures were revealed at low tide, particularly where the protective ring of mudbanks once ran along the low-water line. These structures represent the earliest memories of archaeological features exposed on the foreshore: they were Saxon fish-traps that would soon become synonymous with the Blackwater estuary.
The winter of 1962/1963 saw the ‘Big Freeze’ when the foreshore and saltmarshes were covered in a thick layer of snow. When it finally melted, billions of shellfish and the last of the eel grass had died, leaving the landscape resembling a wet desert. Human activity further damaged this fragile ecosystem, when chemicals in the form of tributyltin (a new anti-fouling paint used on the hulls of boats) further polluted the water, threatening the dwindling number of shellfish. By 1980, the high-water line had moved far enough landward to increase the salinity of the ground, allowing salt-tolerant plants to dominate land formerly rich with terrestrial grasses. Most of the creeks in West Mersea became blocked entirely by erosion-driven sedimentation. In East Mersea, the gentle slopes of Cudmore Grove were undermined and exposed, creating vertical cliff-faces more susceptible to wave erosion. The recession of the cliffs brought coastal defences from the Second World War dangerously close to the edge, while marshland to the west of the cliffs virtually disappeared.
The harvesting of winkles and cockles ended as natural foreshore stocks were depleted, while native oysters – a popular foodstuff in the area from the Roman period – were no longer found on Monkey Beach by the late 1990s. A run of strong easterly storms combined with increased tidal reach added to ongoing erosion of the coastline, with more powerful waves now striking vulnerable sections of the coastline and seawalls. By the late 1980s, the cliffs at Cudmore Grove had eroded so far back that a chain of Second World War military installations on the clifftop had to be bulldozed on to the beach. Their current location clearly illustrates the scale and speed of erosion over the past 30 years: indeed, over 1m of recession has occurred just since 2017 at Cudmore. Moreover, during the 1980s the tidal scour had increased so much that archaeologists conducting the Hullbridge Survey were able to record archaeological features exposed on the open foreshore for the first time in millennia. Several timber structures were documented off Mersea, representing part of a Bronze Age land surface dating back 3,000 years.
By examining the data gathered for the CMCC project, we can clearly see that many factors have contributed to the complex changes that have transformed Mersea Island’s coast over the last century. To begin with, there are all-too significant changes in coastal biodiversity. At Monkey Beach a century ago, the foreshore accommodated a rich range of shellfish, lugworms, and seagrass: that diversity has now been all but destroyed. Naturally driven coastal erosion cannot solely account for such devastation. Although major storms, flooding, and deep freezes have had measurable impacts, so too have the introduction of agri-chemicals, increases in shipping, changes in land management and drainage, and waste from industry and other pollutants.
We have learned that a healthy, richly biodiverse foreshore environment can provide a natural and effective check against some of the forces of coastal erosion. But humans have the capacity, knowingly or unknowingly, to alter the delicate ecosystems, often with an impact only felt by future generations. Indeed, it was the loss of eel grass that proved pivotal, since it increased the speed of erosion over the last 50 years, resulting in the radically changed foreshore we see today. It seems that it was the increasingly aggressive interaction of artificial with natural processes that was a major driver in accelerating the rate of coastal change on Mersea. Humans were effectively amplifying natural processes beyond the point that nature could recover. One set of determinants is thus ostensibly within our control; the other set we must adapt to. We now know what happened in the past. So, what might happen to our coast in the next century? And what can we do to change that future?
CITiZAN’s work in Essex has shown the value of recording and studying the threatened coastal heritage that is so crucial to our island story. But it has also shown that such eco-archaeological surveys have a wider role in enhancing public understanding of the significance of ever-increasing tidal scour and coastal erosion, with its all-too tangible relationship to climate change. This study was only made possible by accessing the detailed, intergenerational knowledge retained by the Mersea community, one that lived next to the sea all year round, often visiting the foreshore on a daily basis for work, for pleasure, or for both. Their photographs, their memories, and their keen observations founded on a long-lived personal attachment to the coast brought a level of detail to the complex story of change that more formal or more remote scientific models would struggle to achieve. Above all, our project has demonstrated that the collective voice of an island community can be powerfully perceptive when debating issues such as the consequences of coastal and climate change, illuminating impacts not just relevant locally but at national and international levels.
The message from Mersea Island’s coastal eco-archaeology project is clear: it is the unanticipated impact of interactions on the ecosystem (notably in the last 60 to 70 years) that have demonstrably exacerbated the longer-term impacts of climate change on an already vulnerable coast. If we can learn those lessons from the past and develop solutions for working more harmoniously with coastal environments, we can be better prepared for the inevitable by being more adaptable and prepared to work with natural processes, and thus more effective and creative in our approach to flood resilience and coastal erosion. By exploring the past, the future lies in our hands.
The Mersea Island Discovery Programme team acknowledges the work of Mark Dixon, Jane Dixon, James Pullen, Carol Wyatt, John Pullen, Daniel French, David Cooper, Joanne Godfrey, Tony Millet, and Gustav Milne.
Oliver Hutchinson is CITiZAN Discovery Programme Officer for Mersea Island, and Lead Archaeologist for the CMCC project. Danielle Newman has been working as the Community Archaeologist for Mersea Island since January 2020. Lawrence Northall is the CITiZAN Community Archaeologist in the South East and worked on Mersea Island from 2018 to 2020.
ALL IMAGES: Courtesy of CITiZAN.