To the Bronze Age in search of a Tsunami

In 2012 Druridge Bay’s ponds and wetlands teemed with invertebrates flourishing in the summer-long floods and were waist deep in rushes, grasses and herbs. This summer the ponds dry and crack in the July heat-wave, their wildlife hunkered down, plants desiccated or grazed as livestock can now reach the swards that were behind deep moats of unseasonal flooding last July. These two years capturing a powerful example of how the ecology changes, but the Bay currently offers a more striking example of changes through time and landscapes, but also of human continuity. Along the dune front at Low Hauxley Archaeological Research Services are leading a dig to record the Bronze Age burial sites that had been revealed as dune erosion cut into a burial cist. The dig, "Rescured from the Sea" has been a revelation. The occasional burial remains had been known for many years but the dig has unearthed two arcs of large stones, the half circle outline of a Bronze Age cairn (far edge of site in photo), the outer half having already been washed away by the tides gnawing at the dunes. A few metres inland, and unexpectedly, an Iron Age round house is traced in the sand (right, foreground), with at least two hearths and what one digger described as a crazy paving patio out the front. Stone Age finds have also appeared in the concreted sand base of the site, perhaps from the same people who left their foot prints in the peat beds which are occasionally unveiled when winter tides rip back the sand from the adjacent beach. The Bronze Age site looked across a kilometre of land to a distant shore line, a world of wet woodland populated by red deer, wild boar and huge wild cattle known as Aurochs, a world which has been preserved in the peat beds along the dune face (Blog, 5/12/2012 and 10/12/2012 ). The continued use (or perhaps revisiting) of the Hauxley site from Stone Age, Bronze age through to Iron Age is a compelling tale and perhaps one laced with startlingly sudden change. The archaeologists are now digging down at Hauxley to search for evidence of the North Sea Tsunami, which occurred ~8000 years ago, a tidal drive driven by colossal undersea sediment slides, the Storegga slides, off the east coast of Norway. The floods of 2012 and heat wave of 2013 are much smaller events, but work with the archaeology to show just how dynamic this landscape can be. The diggers happily show you around at 11am or 1pm everyday, so get along and take a trip through time

Cows, coypu and the ectozoochory taxi

A July heat wave has clamped down over England. Radio Newcastle asked people to text in with the temperature in their office or car; often over 30^oC. Up at Druridge Bay the dune grasses are being spun into sward of the finest golds and silvers, bleached and glittering in sunshine. The ponds which last year were overflowing have largely dried. The few which retain a hint of damp have become a haven for cattle, a mini-migration. Here is a subsidence pond at the south end of the Bay, in a pasture field, the cattle homing in on the cool soil amongst the grasses and rushes left by the hay cutter. The cows seem to mark out the pond’s outline with a precision to match any surveying I could do. The drying out is compounded by heavy grazing and quite bit of pooing.

This pond was a verdant swamp of spike rush and jointed rush a year ago, but the clumps of rushes are now bitten down to stumps and the mud poached by hooves. I’d like to know if the livestock can carry pond life from site to site; ectozoochory, to give hitch-hiking on an animal its scientific name. Whilst the expansive bulk of cattle seem a likely form of transport smaller animals can be good vectors too. One of my favourite studies is of things washed from the fur of coypu living (or, had been living) in the Carmargue in the south of France. The coypu had been shot, not part of the study, but as a control programme and Aline Waterkeyn and her colleagues hosed down the corpses to see what the coypu had been carrying. Waterfleas and rotifers, midge larvae and worms, Ostracods and springtails all came off in the wash (Hydrobiologia, vol 652, pp267-271). The water-fleas were particularly species associated with aquatic plants, which fits the herbivorous habits of the coypu. I have a soft spot for coypu, having watched them when I grew up in East Anglia. They would come out of the wetlands and “moo”, slightly forlorn, as if aware of their unloved status. I tried coypu curry once too. The coypu are gone from England now, eradicated due to their impact on crops and river bank defences. Like the coypu of the Camargue the cattle of Druridge Bay are likely vectors, and they moo.

Bad year, good year. Or, perhaps the opposite

The photos above show the margins of a subsidence pond in one of the pasture fields north of Cresswell village. On the left hand side the pond in July 2012, as the record breaking wet summer swelled the wetlands throughout the Bay. To the right the same pond in July 2013, as the first proper heatwave since 2006 takes hold. The weather during 2012 was a startling combination, opening up with a lingering winter drought that broke in April, to be followed by weeks of high rainfall punctuated by occasional exceptional downpours. Homes were flooded, roads closed or washed away and crops destroyed. Wildlife certainly suffered, most conspicuously the familiar butterflies of summer with the often overlooked cabbage whites suddenly becoming things of rare and flimsy beauty. This year seems better, although the high summer skippers and brown butterflies are taking their time to first appear on the wing. But which pond looks in the best health? In 2013 the same pond is but a puddle, the rushes and grasses stunted and grazed. Admittedly in 2012 no sheep or cattle were kept out in the fields, instead taken inside to weather the weather, so this year the verdant grasses, including the likes of the very palatable Flote grass, (Glyceria fluitans), have been nibbled to stumps. Again, 2012 looks in retrospect, like a boon year for many of the wetland plants.

Parliament, ponds and extreme weather

The Houses of Parliament are so familiar that it is easy to forget just what an extraordinary confection of ornamentation they are. There is not a square inch lacking in Victorian flourishes of heraldic arms, gothic crenulations and worthy relief sculpting. Standing outside the Palace the whole structure radiates a slightly alien feel, as if inside its own protective force-field amongst the throng of tourists. I was there for the launch of The British Ecological Society’s latest publication, a review of the impacts of extreme weather on freshwaters in the UK. A tricky document to pull together because studying extreme events is an ad hoc science, replying on unforeseen opportunities as drought or flood strike the UK and often lacking reliable data from before the crisis against which any impacts can be judged. Nonetheless the review pulls together evidence from lakes, rivers and ponds and paints a fascinating picture of the changeability and resilience of our freshwaters. The broad message is that our freshwaters are vulnerable and can show rapid degradation, but nature bounces back so long as there are refuges elsewhere in  catchment or wider landscape from which the wildlife can recover (the whole document can be downloaded at http://www.britishecologicalsociety.org/public-policy/our-position/ecological-issues/)

Northumberland, and Druridge Bay, feature large in the review, because I helped write the report and they are what I know best. In particular the Hauxley experimental ponds are an unusual example of a long term study, around long enough to have been hit by extreme rainfall and prolonged droughts. The impacts of the June 1997  deluge in Northumberland, an event so unusual that it may be a 1 in 300 year event, are shown in the report in photos of the River Wansbeck strewn with ripped up bulrushes and the Hauxley ponds are pictured because of the thick mats of algal that developed when the ponds did not dry out, with the result that other wildlife was partly smothered out. Odd but also charming to be thinking of Druridge Bay and Hauxley in the wood panelled grandeur of the palace of Westminster, crackling with power and the hushed sound of crustless finger sandwiches being hoovered up.

Ponds and the creativity of extreme weather

2012 has become infamous as the wettest year on record in England. Infamous, at least, in England. This has been followed by a peculiarly long winter, the coldest for fifty years. Britain has had a run of wet summers. One outcome was a recent meeting by climate scientists hosted by Exeter University to try and make sense of the signals from the noise and ,perhaps, the causes. The immediate driver appears to be the jet stream, which has not been shifting as far north has it once did and, instead, acts as a conveyor hauling Atlantic depressions across the UK, one after the other. However what causes the jet stream to linger so far south remains unclear (http://metofficenews.wordpress.com/2013/06/18/meeting-on-uks-run-of-unusual-seasons/) . Ponds make immediate and powerful indicators of the impacts of these variations in our climate. The photos above show one of the subsidence ponds at Blakemoor Farm in the summer of 2012, when it was festooned with deep banks of Celery Leaved Buttercup, to summer 2013, when it has dried out, leaving a few forlorn tufts. What is the most worrying; being awash or being dried out? Neither. The pond comes and goes and with it the vegetation. The animals are less obvious but they too wax and wane between years. The extreme year of 2012 created an opportunity for plants and animals that seldom colonised or, even if they did, dominated the ponds. The ability of a landscape to vary  has always struck me as important, although a tricky thing to measure, given how short term so much of our research is. We find it hard enough to describe what we can capture and count, letalone something as abstract as the potenital to change. The variation between years has added to the overall biodiversity, allowing wet and dry year communities to flourish. The risk is that we have not recorded enough data for sufficient years to spot any major step changes, those thresholds beyond which the stage is re-set and some of the cast of ecological characters  never re-appear.

The fairy fern hints at summer

There are signs of summer in a bucket in my back yard in Newcastle: the fairy fern has sprouted green shoots. Green, feathery branches have grown out from a reddish base, visible in the photo amongst the smooth round duckweed plants. Fairy Fern, Azolla filicoides, is a native of the west coast of the USA, not that these tiny individuals came over the Atlantic. They came from Ellington at the south end of Druridge Bay. The large pond in the village has harboured these New World arrivals for many years. The ones in the bucket in my back yard were a test to see how they would fare through the winter, being plants of warmer climes. Would they cope with being iced up? They were frozen into a solid block of ice, the ferns turning a blotchy red, which seems to be a cold weather response, but they survived and now are sprouting delicate, doily-like new growth.
 

In a warm year they form a dense mat over the surface of Ellington pond, deceptively like a lawn but, on closer inspection, a serrated fuzz of fronds oddly resembling the jagged canopy of a conifer plantation in miniature. For me the dense mats seem to coincide with drousy, heavy weather, thunder threatening through the heat in late August. In a bad year, when the cold and wet do not suit their west coast roots, they hunker down in circular rafts, nestled amongst the other plants around the edge of the pond. The managers of Ellington Pond have tried to be rid of it, but even one tiny frond is enough to retain a bridgehead and begin the recolonisation. Quite how Azolla got to Ellington remains a mystery and the fronds have not turned up further north in England, although a scatter occur throughout the Central Belt in Scotland. There is a touch of exotic mystery to its presence, almost a glamour, entirely consistent with the Bay’s sense of being between worlds.

The fret of June

June opens with a week of proper summer warmth, an immediate slap of sunshine you can feel faintly crisping you skin. Sunny days along the Northumberland coast can have a mysterious quality. Out over the sea there are low banks of grey and brown clouds that drape from horizon to horizon a bit like those curtains around beds in hospitals. The North Sea is lost behind them. These are banks of sea fret, condensing out over the cold water. Up at the Bay the fret has been advancing and retreating in probing attacks. Tongues of sea mist drift in for an hour or two, swathing a field or dune, the sun still visible if you look up through the shallow pall of mist, then pulling back to the sea. The fret brings a tingling, hair-on-the-back-of-your-neck drop in temperature as the moisture drifts past. The droplets shred and catch on hawthorn and bramble, traces of mist visibly rolling and tumbling inland then retreating back to recharge out at sea. This has been a dry spring and the subsidence ponds in amongst the field drops are shrinking, some barely wet. The deluges of 2012 resulted in verdant borders of Celery Leaved Buttercup, Toad Rush and Pineapple Mayweed turning many of these pools into vivid summer circles, but 2013 threatens the opposite. This begs a question of those of us who regularly survey pond sites: is one year’s data, a snapshot, sufficient to characterise a pond? Probably not, or, at least a snap shot cannot capture the extent of change across the pondscape. Some ponds do not seem to vary much from year to year. For others the very variability is their most striking feature. One boon to the work at Druridge Bay is that we have got to know the sites well and have sense of time as a factor in the ponds’ ecology. This year I’ll be re-surveying the vegetation of the ponds at Blakemoor to compare to the summer 2012 plants. For now though I’m enchanted by the fret seeming to briefly stop summer and hide the ponds from our gaze.