Monday, 25 October 2010

Climate Catastrophes and the Écréhous

It is instructive when looking at the present, where we seem to be entering a period of increasingly volatile weather, with violent storms, and increases in flooding, that this kind of volatile weather is nothing new, and we may have to brace ourselves for a period of very catastrophic change.

I'm not assuming much about causal factors which may have been involved, and which may have been quite different from those of today, but simply noting how climatic changes can introduce very unsettled weather, capable of reaping great devastation across the European landscape, and which have largely been forgotten.

The 13th century (1200-1300) seems to have been a time of well documented (not legendary) storms which caused severe coastal erosion in France and England, and locally one of the most significant losses of land mass appears to be the Écréhous. In the book on the reef, Warwick Rodwell suggests the archeological evidence points to a significant reduction in land mass (so that the Écréhous could no longer easily support the monastic community). There was also a small but significant rise in sea level.

An example of how damaging the storms were can be seen in the UK, where numerous storms and a rise in sea level destroyed the port of Old Winchelsea and the River Rother altered its course from its exit to the sea at New Romney to a new position near Rye. This was due to the inundations of the Marshes after the great storms from 1234 to 1336.

Also in the Netherlands: the storm Grote Mandrenke (Great Drowning of Men) strikes the Netherlands in January 1362. Hurricane-force winds with enormous waves and a considerable sea level rise (a storm surge) due to the combined action of push by the wind and lifting of the sea surface because of low air pressure flooded extensive areas of the Netherlands, killing at least 25,000 inhabitants. This number should of cause be seen in relation to the much smaller population at that time than now.

The storm also flooded and eroded large land areas in western Slesvig, Denmark, whereby sixty parishes disappeared totally. Also southern England was severely hit by the storm, with much damage on buildings and infrastructure. The 1362 storm resulted in severe coastal erosion, contributing to the opening of a pre-existing topographical low in the Netherlands towards the North Sea.

Returning to the Écréhous, Warwick Rodwell in his synthesis of the examination of the region mentions this:

" The progressive inundation of the French coast during the Middle Ages, and earlier, is a subject that has preoccupied numerous antiquarian writers. A string of dates has been cited when major storms and floods are alleged to have occurred, resulting in great land losses. Among the early data cited, 709 is the most persistent, but 541 and 603 also receive mention. Later inundations consequent land losses are well tested, especially in the 13th and 14th centuries. " (p363)

A "cross-bearing" comes from the pollen examined, which reveals a larger shoreline than that of today, and suggests there might well be a basis in history for the possible 709 land losses:

" It is worth noting that pollen sequence examined in the ancient soil of the marsh on La Maître Ile is relevant to the environment in the early Christian period. The pollen reveals a substantially different vegetation regime from that obtaining today, although confirming the location was close to a shoreline. The presence of a broad range of free pollen in each of the palynozones examine is interesting, especially the occurrence of fir in the lower levels. Taken at face value, this implies woodland on the Écréhous in early historic times.. " (p366)

Regarding the later land loss of the 13th century, the evidence is for a larger population of monks (because of the expansion of the buildings) and the archeology shows again another "cross bearing" on the incursions of the sea:

" St Mary's Priory was, in its own modest way, prospering in the middle years of the 13th century. The new chapel [built in this period] bears testimony to this; so does the addition of other buildings to the nucleus. Although little now remains it appears that a substantial rectangular structure was added to the West, which we may suspect was a new common hall. It was however destroyed -- seemingly in the 13th century -- by the inroads of the sea from the West. We have here a specific piece of archaeological evidence for marine transgression, in a period where there are numerous historical references to catastrophic incursions by the tides. " (p367)

" If the sea could engulf recently built structures, and penetrated within a few metres of the West End of the old chapel and hall, the implication must be that the reef had fragmented and shrunk to something approaching its present form by the 14th century. .. The Assize role of 1309 speaks of only two monks and a servants, and of the hardship of life on the Écréhous. The Priory was in decline and the prior's complaint of the poor conditions of the grounds was probably not an exaggeration. " ( p368 )

John Renouf, on the geology, notes that there is nothing against a rapid land loss, as the geological evidence does not say anything one way or another (he does note that the "legend of the plank", however, is in direct contraction to the geology of the region). But the supposition is of a much larger Écréhous in historical times, one still cut off by the sea from France and Jersey, but undergoing cycles of stormy weather when erosion took place very rapidly:

" while the physical evidence cannot be used to prove a greater land area, it also has nothing to say gained such a situation. .. The climatic deterioration began after A.D. 1200, and had such dire consequences in our immediate area from the first half of the 14th century, is the most likely moment for serious inroads to have been made into any greater land area that existed hitherto on the Écréhous "

Incidentally, the well was examined closely, and is designed for ground water; it does not - contrary to water diviners - go deep in the bedrock to hidden underground streams:

" The well on La Maître Ile is undatable but could be mediaeval, and may have been contained within a circular well-house. The shallowness of the feature -- which hardly penetrates the solid rock -- demonstrates that it is essentially a cistern or dipping-well deriving its supply from surface water, and not from an underground spring. " (p73)

Again the archeological evidence is that in the early Middle ages, there could well have been live animals on the reef; the middens show:

" bone assemblage comprising sheep, pig and cow. These together with hare/rabbit, clearly comprise the principal types of red meat consumed on the grounds and the archaeological evidence points strongly to the existence of live animals on the reef not of importation " (p356)

Rodwell draws this in his synthesis for a larger reef until the storms of the 13th century:

" The implications for the historic environment keeping sheep, cow and pig on the Écréhous - even if the only in small numbers - are considerable. First there must be adequate salt free vegetation for grazing. Secondly the ground conditions had to be suitable for keeping and probably for breeding animals. In the case of cows and sheep, a significant area of fresh grass was a basic requirement. Nor could water locked ground be utilised since that would cause foot rot. " (p356)

and he contrasts this with the position today:

" The tiny area of grass to grow on the marsh on the Maître Ile, whether or not it was waterlogged, could hardly have supported more than a single cow. " (p356)

In conclusion, it is certainly clear that during the 13th and 14 centuries, perhaps as the Medieval warm spell came to an end, the weather became increasingly violent, and the effect of this can be seen in the Écréhous, although they would have undoubtedly been also having an effect on the softer shale rocks of Jersey.

It is dangerous to predict too much from the past, but the increasing prevalence of violent storms in Europe certainly suggests we may be entering another period of very unsettled and stormy weather, and the incidence of flooding, wind damage, and coastal erosion (despite sea wall defenses) may well be significantly greater than during the last century.

The Écréhous, edited by Warwick Rodwell, 1996

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