The coast has an ephemeral quality, changing almost constantly. The level of the sea waxes and wanes over a multitude of timeframes, daily with the tides, showing dramatic increases in tide levels during storm events, as well as showing changes over longer periods through geological uplift or subsidence of the land, or alterations in global sea level. The level of the sea is constantly changing – and so too is the shoreline itself. The rocky cliff faces, the sandy dunes, and the soft glacial drift cliffs, which make up so much of our coastline, continually undergo changes as material is eroded away, and material is deposited. The evidence for this continual process of change is sometimes dramatically preserved. Submerged off the Bray coast in Co. Wicklow, lies the remains of a forest over six millennia old.
At the end of the last Ice Age, what we know today as the coast of north Wicklow was forested dry land. As the climate changed during this period, the gradual increase in global sea level inundated the land and pushed the coastline further and further inland. The ancient shore and forest of north Wicklow sank beneath the waves ….. and there it remained, buried beneath sand and sea and surf.
The submerged forest of Bray was first noted by Robert Lloyd Praeger in the closing years of the 19th century. The construction of Bray Harbour between 1891 and 1895 changed the patterns of sediment transport in the south of Kiliney Bay causing a drop in beach level. As the beach level dropped, the ancient forest of Bray emerged from the sands to the north of Bray Harbour. Praeger noted a forest of collapsed “Scotch pine trees” amid a layer of peat. The concept of a submerged forest had always intrigued me, and during 1999, I re-examined the site with a view to assessing how the forest had changed over the 20th century.
The aim of my survey was to establish the extent of the submerged forest, and compare this to the photographic record made by Praegar a century before. The initial results were ominous – Praegar had recorded the remains of a collapsed woodland with trees lying on top of trees. Yet during over 10 months of survey and monitoring during 1999, only three trees were partially. One of the trees was exposed during the lowest tides, the other two were found at a depth of four metres. The results of the 1999 survey raised a range of questions – including the possibility that the forest surveyed by Praeger had almost completely disappeared in just a century. Had everything been destroyed by the merciless onslaught of the sea? Was there anything left preserved beneath the shifting sands? The surf and sands had taken their toll on the coast – shipwrecks, martello towers, cottages and the railway hadn’t survived …….. was the forest gone too?
The three surviving trees exposed in 1999 were identified as Scots pine, and samples returned a radiocarbon date of 6,180 (+/- 80) years before present. Scots pine, or Pinus sylvestris, is also know as Scotch pine – and is more commonly known in the timber trade as ‘redwood’ or ‘deal’. Scots pine is the most widely distributed pine in the world. It can be found in a broad belt from northern Scotland to Spain, across northern Europe, Scandinavia and northern Asia to the Pacific. It was also introduced to the United States and southern Canada by early colonists. The trees are typically 25-40m tall, 0.5–1.2m in girth, and have an average lifespan of 150 years, though a living tree in Sweden is currently 711 years old. Certainly, traces of the submerged forest survived – but the tract of woodland exposed 100 years previously was not in evidence.
In February 2001, the beach levels of the north strand of Bray dropped by an average of one metre – and suddenly sections of the forest were exposed again. 35 trees could be seen during low tide periods found in two locations. The area where only three trees had been found in 1999 suddenly seemed full of stumps and branches and trunks sticking every which way from the sand and surf. A second area further north also showed tree trunks lying exposed at low tide amid a confusion of boulders. The fall in beach levels also exposed a layer of peat embedded with pine cones and other organic material. Up to seven metres in length of trees protrude from the shifting sands – their smooth surfaces polished by water action and abrasion by beach cobbles. The lesser branches are gone, and even the substantial root systems are washed almost smooth. The trees and the layer of peat are washed by wind and wave, and are a poignant reminder of the fragility of the traces of the past which have survived to the present day. The surviving trees stand mute sentinels to a landscape long disappeared beneath the waves.
The submerged forest is not the only part of our coastal heritage at risk. The cliffs between Bray, Co. Wicklow, and Kiliney, Co. Dublin, have a long history of erosion. The cliffs suffer continual erosion at high tides and sudden collapses of the cliff face are a normal occurrence during storm events. The rate of erosion averages over one metre per year, and this has led to the loss of substantial portions of the natural, and the historic built environment in the area. Over the course of the 19th and early 20th centuries, two martello towers, a number of dwellings, and the Dublin to Wicklow railway line were undermined and collapsed into the sea. The remains of the granite ashlar railway embankment stretch from Bray to Kiliney and are entirely submerged at high tide. The granite masonry shows clear signs of accelerated weathering, and the recent collapse of sections of the railway bridges at both Bray and Greystones pay testament to the continuing encroachment of the sea on the east coast of Ireland.
The cycle of burial and re-emergence of submerged forests, often inaccurately referred to as a ‘petrified forests’, is not a local phenomenon, but can be seen around the Irish coast, and internationally at submerged forests in the USA, Canada, the United Kingdom and further afield. Ironically, a factor in the continuing survival of these forests, and of archaeological material in the inter-tidal zone, may be the continuing rise in global sea level expected through the 21st century. As the submerged forests sink deeper beneath a rising sea level, they enter a relatively more stable environment, perhaps facilitating their survival for generations to come.
The continuing survival of submerged forests, and of coastal monuments and heritage in general, is dependent on the interplay between a wide variety of factors. What is becoming increasingly clear, however, is that in a fast-moving world, our heritage is as subject to the forces of change as the other threatened elements of our built and natural environments.
Acknowledgements: The survey of the submerged forest received support from the Heritage Council under the 1999 Community Grants Scheme. The survey was carried out with the assistance of the Irish Maritime Archaeology Society.