Through The Sandglass

Europe's inland sand seas (2): Dutch deserts and geoconservation

 

Last week, I wrote about the strange history of wind-blown sand in the pastoral English countryside, and the dunes that invaded Santon Downham in the "great sand flood." This area of East Anglia lies at the eastern end of the European sand belt, a great swathe of lowlands covered, more or less, by aeolian sand deposits originating from the chaos left behind by the retreat of the Ice Age glaciers. Leave eastern England and cross the North Sea to the Netherlands and you will find, perhaps surprisingly, a country half-covered in sand - not including the coastal and estuarine systems. The map below is taken from a new publication by Eduard Koster of the University of Utrecht that is, admirably, open-access; The “European Aeolian Sand Belt”: Geoconservation of Drift Sand Landscapes can be downloaded in full from http://www.springerlink.com/content/a74hr7168667nh21/. The "cover sands" shown on the map are exactly that, the foundation cover of sand spread out over the post-glacial landscape and forming the source for the wind-blown deposits of "drift sand." It's estimated that drift sands cover perhaps 4,000 square kilometers of northwestern Europe, almost entirely stabilised by artificial and natural vegetation. Almost entirely, but, as we know from the Santon Downham experience, not completely - small patches of active, drifting, sand remain and they are of considerable interest both for their ecology and for their role in geoconservation efforts. The areas that Koster focuses on are around Veluwe, and a group of these dune areas around Hulshorster is shown in the Google Earth image at the top of this post.

 

Like the drifting sands of East Anglia, these areas have a dynamic history, the latest phase of which has been significant reduction in size. Re-forestation and agriculture have conspired with natural vegetation spread, in part stimulated by the increasing nitrogen levels from manmade pollution. The Hulshorster dunes, up to 20 meters in height, have been gradually stabilised over the last century, covered by a variety of algae, lichens, mosses, grasses, heather, and pine trees; tree planting upwind of the dunes has starved them of sand supply. In 1900, the two largest areas of sand in the Google Earth image were continuous, an area of around 4 square kilometers but by 2006 this had been reduced to a mere 0.35 square kilometers of bare sand. But historically, the areas of active sands have been significantly larger, periods of remobilisation alternating with soil development (photo, right), and following a timetable that can be broadly correlated with the sequence of events described from East Anglia. The first phase of extensive drift sand formation took place during the eleventh to thirteenth century AD, followed by a second phase during the sixteenth and seventeenth century - the Little Ice Age period and the burial of Santon Downham. But the activity can also be documented from much earlier - the remains of a small, thriving, 8th and 9th century village have been found beneath the drift sands; somewhere in between 950 and 1000 AD, this village had to be abandoned as the local water wells began to dry out, and the farmland became increasingly covered by drifting sands.

These dwindling miniature landscapes of active sands represent extremely complex and unique environments, now protected as European Union Habitat Types; substantial changes in their ecology have been recorded in recent times as the extent of the environment can no longer support the unique ecology.  As Koster writes:

Unvegetated drift sand areas constitute a very specific habitat for plants and insects due to (a) the very nutrient-poor substrate, (b) the continuously changing environmental conditions related to sand movement, and (c) the exceptional microclimate in which daily temperature ranges of more than 50°C and extreme changes in soil moisture content can occur.

So, what to do? As Koster describes, it's a complex issue, but a variety of authorities in the Netherlands have embarked on projects to better understand the character and dynamics of these environments as a basis for planning geoconservation efforts. "Geoconservation" has been defined as "action taken with the intent of conserving and enhancing geological and geomorphological features, processes, sites and specimens,” an agenda distinct from more traditional conservation initiatives  - and one that all of us should thoroughly endorse.

In all European countries, attention is given to landscape preservation; however, policy and practice in the past have mainly been based on specific biological, historical–cultural, and visual landscape qualities. Although the geological aspects are the essential foundation for these values, they seldom formed the primary basis for the preservation policy (Kloster)

Geoconservation of Europe's active inland dune areas has to involve the wholesale removal of thousands of trees, scrub, lichen, and algae-covered soil and sand - not always an easy action to take. Small but ambitious pilot projects are already underway - compare the photo below of the Hulshorster dune area, taken in 1985, with the image at the top of this post.

And, given the varied history of sand activity, together with the unknowns of future changes in winds and climate, it's surely difficult to define what, if anything, constitutes the "natural" condition of such environments; nevertheless, I would agree with the efforts being made - a futile and emotional argument about what is "natural" could easily outlast these unique landscapes. I'll end with Koster's conclusion:

Modern concepts of nature conservation and rehabilitation on the other hand now lead to restoration of the originally dynamic drift sand ecosystems. However, it is inevitable that reactivation projects that primarily promote sand drifting processes may come into conflict with classic habitat strategies that aim to achieve maximum biodiversity and natural vegetation succession....In conclusion, inland dune landscapes where aeolian processes of sediment transport and deposition can be observed and investigated are very rare in northwestern Europe, in fact, much more rare than in coastal dune landscapes. Moreover, the dynamism in these landscapes, i.e., the geodiversity of these areas, forms the basis for an exceptional biodiversity. Areas where an ecological gradient exists from bare sand surfaces to partly stabilized surfaces with pioneer plant species to the first stages of forest succession next to each other are equally rare in northwestern Europe. However, geoconservation of these important “natural” landscapes needs careful planning and management that requires a profound knowledge of the interaction of the many geomorphological, ecological, and land use processes.

 [My thanks to Richard Cathcart for drawing my attention to this paper and this topic. And I'd be interested to hear from readers in the US - a quarter of the State of Nebraska is covered in sand dunes: are there similar discussions and initiatives going on there?]

Commercial break - Meet the Author

Once again I shall cast all modesty aside and insert a bit of advertising. Meet the Author is a great idea - writers record very short podcasts talking about their books; this is available on the net both in the US and the UK. I have to admit that I only became aware of it recently when I was asked to do one, but I now root around the site to see and listen to people whose books I have enjoyed - or wonder whether I might enjoy. So, if you are twiddling your thumbs and at a complete loss for something to do for three minutes, go to http://www.meettheauthor.co.uk/bookbites/1888.html

And while I'm on the trumpet-blowing podium (the trumpet being an instrument that in reality I did, and occasionally still do, play), I just discovered that the North American edition of the book received the Honorable Mention in the Nature and Environment category of the National Outdoor Book Awards, for which I'm flattered and very gratified.

Europe's inland sand seas (1): a sand flood and Norman rabbits

 

The little village of Santon Downham, on the border of Norfolk and Suffolk in East Anglia, is today a pleasant, if not particularly remarkable, example of bucolic English hamlets. But it has one extraordinary claim to fame: in the middle of the seventeenth century, over a period of several years, Santon Downham was almost overwhelmed and buried in sand - the great "sand-flood." Dunes several meters high piled up against walls and houses, and sand choked the nearby river. Even a century later, a visitor's account describes "….such a piece of absolute desert almost in the heart of England ..... Nothing was to be seen on either side but sand and scattered gravel without the least vegetation; a mere African desert." 

Sandstorms and migrating dunes in the English countryside? This whole area of East Anglia, a low-lying and very dry area of heath known as Breckland, or "the Brecks," is covered in sand beneath the surface, sand that was derived from the geological rubbish left behind by the Ice Age glaciers and the meltwater rivers that poured across the bedrock chalk of the region. As climatic conditions - and man's activities - changed, the sands would become active and accumulate into dune fields, marching across the Brecks. Periods of activity were interspersed with periods of stability, the sands covered by soil until they broke free once more. A first-hand account of the inundation of Santon Downham was written by a resident, Thomas Wright, who, in 1668, described in a letter to the Royal Society, published in its Philosophical Transactions, the encroachment of the sand and his struggles to preserve his house; he also suggested the origin of the sand and his ideas turn out to be quite accurate. For a very modest sum, the original letter can be downloaded from the Royal Society archives, and it makes for fascinating reading. Here's the title (remember the old ufe of "f's" for "s's"):

 

The body of sand, the "wing'd enemy," had been on the move for decades, grown to cover more than a thousand acres, and reached the outskirts of the village 30 or 40 years before Wright's account. There it paused for ten years "without doing any considerable mischief" but then took off, and "over-ran 200 acres of very good corn" in less than a year. But then Wright wrote, "'Tis now got into the body of this little Town, where it hath buried and destroyed divers Tenements and other Houses, and has inforc'd us to preserve the remainder at a greater charge than they are worth." Wright and the other villages struggled to fend off the dunes over a period of five years: "For, it had so possest all our Avenues, as there was no passage to us but over two Walls of 8 or 9 foot high (which encompass'd a small grove before my house, now almost buried in sand); nay, it was once so near a conquest, as at one end of my house it was possest of my Yard, and had blown up to the eves of most of my out-houses." Wright resorted to planting "furre-hedges", one of the earliest references to the use of conifers in Breckland. And then, month after month, he planted more on top of the newly-buried ones. He eventually ended up with "sandbanks nearly 20 yards high." These, with the help of his neighbours, he covered with "some hundreds of loads of Muck and good earth," and cut a passage through to his house. These early attempts at dune stabilisation seem to have been effective. Today, the geological map shows the entire area still covered in sand, and the remains of dunes are visible in some places, but otherwise there is no sign of the great "sand-floud." Not that sand isn't still on the move -  in the spring vast piles of sand have to be cleared off roads after high winds, and there are places where cars sometimes need their lights on as they pass through sandstorms.

So where did this "eruption," driven by "the rage of those Impetuous blasts," actually come from? Wright suggests from the warrens of Lakenheath and Wangford, just a few kilometers southwest of Santon Downham; recent work by Steve Godby from Anglia Polytechnic University in Cambridge and Mark Bateman of the University of Sheffield suggests that he was, living up to his name, right. The warrens (and yes, rabbits do come into this) are areas of disturbed sand dunes, more or less overlain by scrubby vegetation and planted pine trees (see the photograph at the head of this post, courtesy of Martin Sandford), next to the American Air Force base at Lakenheath, where the construction of the golf course must have essentially been an exercise in isolating the bunkers (sand traps). As a personal aside, I was intrigued to discover this because, as a graduate student, typically struggling to make ends meet, I taught geology evening classes for the University of Maryland programs at various air bases, including Lakenheath - little did I realise that I was in the midst of a great landscape of sand or that I would be writing about it these many years later. But, back to the warrens. Godby and Bateman have established the chronology of the periods of activity and stability of the sands using luminescence on the sands and radiocarbon dating on some of the organic-rich peaty soil layers that formed during the quiet periods (luminescence dating is an extraordinarily powerful technique that measures how long it has been since material, for example sand, was last exposed to light - more on this in a later post, but see the excellent USGS discussion).

Five periods of sand deposition have been identified, 6500, 1600-1100, 500, 400-335, and 200-30 years before the present. The 400-335 dates, corresponding to the 17th century AD, come from Santon Downham - these ages are not found in the sands of Wangford Warren, and it's reasonable to infer that this is because the sands were blown out of the Warren and inundated Santon Downham. And the event described by Thomas Wright was not the first - at least one previous sand deposition event has taken place at the village. 

The exact combination of climatic and other circumstances that lead to each episode of sand activation are complex, but some factors around the sand flood event are clear, as described by Godby and Bateman. The period 300 to 600 years ago was drier than average, sea level was relatively low, and, from around 650 to perhaps 50 years ago, Europe was in the "Little Ice Age" - and the 17th century was the coldest in the last millennium. Changes in the North Atlantic circulation caused periods of highly variable conditions and extreme storminess. Vegetation on the sands of Breckland would have been stressed and the sand vulnerable to the "rage of those Impetuous blasts." Furthermore, human agricultural excess had resulted in deforestation and impoverishment of what soils there were. And then there were the rabbits.

The Normans brought not only a whole new language to these islands, but a whole new cuisine. They introduced rabbits to the UK. The Bayeux Tapestry shows the invaders feasting upon arrival on these shores, and my personal interpretation is that the scene below depicts rabbit kebabs and spit-roasted rabbit.

 

Rabbits breed proverbially, and while they were to some extent managed for food and fur, they took over vast swathes of the countryside. The sandy ground of the Brecks was ideal for them but they turned the land into more or less a desert. The rabbits were "harvested," using specially trained dogs (called "lurchers") and ferrets, by professional men and women, the "warreners," (image, right), all this activity generating significant income for the lords of the manor. The picture below shows warreners in around 1925, complete with lurchers and ferret boxes, and Lakenheath Warren in the background. 

Without doubt, the rabbits contributed significantly to mobilisation of the sand dunes already activated by the changing climate and the inundation of Santon Downham. But all this was happening not just in England. The Brecklands and other inland sand landscapes of England lie at the western end of what is known as the "European sand belt" that extends across the lowlands through the Netherlands to the Polish-Russian border and beyond. Coastal dune systems are familiar to all of us, but these stretches of inland sand seas (well, perhaps "seas" is a slight exaggeration) are less well known, and are the subject of some fascinating work going on in the realm of geoconservation. This kind of research in the Netherlands was what originally prompted this whole story - but that will have to wait until Part 2.

{Thanks to Martin Sanford for the use of his photograph at the top, from his flickr photostream that includes several images of Wangford Warren. There is a comprehensive guide to the Brecks at http://brecks.org/default.aspx, and the image of warreners, originally from the Ancient House Museum in Thetford, is from one of their downloadable leaflets; http://www.brecks.org/shared/pdfs/brecksfa.pdf is an excellent environmental and historical resource for teachers. Short summaries of the sand flood and the recent research can be found at http://www.santondownham.org/sandflood.html and http://www.santondownham.org/moderntimes.html. My thanks to Richard Cathcart for starting me off on this - he sent me the paper on the Netherlands geoconservation project, which reminded me of the Santon Downham story that I originally intended to include in the book but which ended up as one of the items on the cutting room floor - back to Richard's reference in Part 2.]

"I'm real concerned about the beach"

 

So declared Dennis Dare, a Manager of Ocean City, Maryland, after the conspiracy of a nor'easter and the remnant of tropical storm Ida wrought havoc along the coasts of the northeastern US over the last few days. His concern was well placed - much of the beach simply wasn't there any more, instead there was a twelve-foot cliff marking the extent of relentless wave erosion. Ocean City engineer Terry McGean, after inspecting the scene, is reported as saying “We lost a lot of dune. We lost a fair amount of beach. We’ve seen worse. Certainly, the idea is that we lose sand and not buildings, so it did its job. Now we get everybody rolling to get it back together”; he went on to describe how when it comes time to reload the beach with sand next summer, it’s going to be more expensive and take more sand than they’d planned for. He said the beach lost between 25-50 percent of its dunes.

"Reload the beach" ? I suppose he must be referring to the time-honoured futility of beach nourishment.

The press reports contain many dramatic images and I shall simply reproduce some of my favourites here, with quotations from the accompanying descriptions.

 

"Coastal community leaders said Saturday they were crossing their fingers that the waves would send enough sand back up onto the beaches that human assistance wouldn't be needed to finish the replenishment, shoring up the resorts in time for the economically vital summer."

 

"In Delaware, tides washed out dunes, leaving several feet of water and 3 feet of sand along state Route 1. Transportation officials say it may take two days to clear the sand."

 

"Several vessels carrying hazardous cargo broke loose from their moorings in Virginia during the storm. Crews were working to stabilize a 570-foot barge carrying containers of chemicals in the Sandbridge area of Virginia Beach. Work crews boarded the barge and were riding out the storm with it, hoping it would run aground and could be towed away when the weather improves. A similar fate awaits a 700-foot oil tanker that broke loose and ran aground on a sandbar in the James River in Newport News, Va."

 

"But even if another storm were to hit today, the sand washed away from the dunes will still be of some help, creating a larger near-shore sandbar system that serves to break the waves' energy as they pound the coast. That effect was apparent Friday afternoon, Tony Pratt, Delaware's shorelines and waterway administrator said. "The waves really were breaking quite a distance from the dune by the end of the day ... and losing a tremendous amount of their energy," he said. 'I like it better when the dune is whole, [but] that sand is still serving a great service. ... It's not like a total loss.' "

"Beach replenishment is a costly endeavor. A project earlier this year in Dewey Beach alone cost $6 million. "We're hopeful that Mother Nature will do her job," said Carol Everhart, executive director of the Rehoboth Beach-Dewey Beach Chamber of Commerce. Since 2001, the Army Corps and others have spent $100 million pumping sand from the ocean onto Delaware's beaches. Building sea walls will cost much more -- a sea wall built in Galveston, Texas, cost $10,000 a foot."

 

"State and local beach officials have credited the dunes with defending their towns' homes and boardwalks from the storm's wrath.

Taking an opposite view is Orrin H. Pilkey, emeritus professor in the Nicholas School of the Environment at Duke University and author of "The Corps and the Shore" and this year's "The Rising Sea," which he co-authored.

Pilkey said it would be a huge error for Delaware to ignore science and not plan for the inevitable approach of climate change and rising seas. He pointed to the damaging Ash Wednesday storm of 1962, when the Army Corps of Engineers erected a dune along the shore in Ocean City, Md., and issued an advisory to restrict development inland of the protective barrier. But homes and hotels eventually moved oceanside, on top of and across the dune.

'The town paid no attention to it -- it had no teeth,' Pilkey said. 'Money speaks -- so away we went.' "

[I couldn't possibly comment further on all this - the images and the quotations speak for themselves. Many of the images are from http://www.delawareonline.com/, and http://www.nj.com/, credits Patti Sapone, Robert Sciarrino, Chuck Snyder, Laura Emmons]

And, for Sand Puzzle #2, thanks to Jules, see the comments on Sand Puzzle #1

Sand Puzzles #1: Cooking pasta

 

 Nina must cook some pasta for 15 minutes. The only way she has of measuring time is a 7-minute sand-timer and an 11-minute sand-timer.

How can she use these timers to measure exactly 15 minutes?

I just came across a website called NRICH, a superb UK-based resource for maths teachers at all levels, a joint project between the Mathematics and Education Departments at the University of Cambridge. I'll let them describe the aims of their project themselves:

NRICH aims to:

• Enrich the experience of the mathematics curriculum for all learners
• Offer challenging and engaging activities
• Develop mathematical thinking and problem-solving skills
• Show rich mathematics in meaningful contexts
• Work in partnership with teachers, schools and other educational settings

For teachers of mathematics, we:

• Offer you FREE enrichment material (Problems, Articles and Games) at all Key Stages that really can help to inspire and engage learners and embed RICH tasks into everyday practice.
• Help to promote RICH thinking in classrooms by offering on-line and face-to-face support at Primary and Secondary level.
• Deliver professional development courses and workshops in rich mathematics.
• Help teachers to think strategically about 'next steps' and progression in problem solving.

And for those learning mathematics, we:

• Provide FREE and interesting mathematical games, problems and articles.
• Encourage you to share your solutions to our mathematical problems.
• Have Mathematicians that can help you to solve problems - just 'Ask NRICH'!
• Offer a safe online space where you can meet others with similar interests.

A note for parents:

• NRICH is a joint project between the Faculties of Mathematics and Education at The University of Cambridge
• Our FREE and extensive Rich Resource Bank has been designed to meet the needs of learners from ages 5 to 19 (Key Stages 1 to 5).
• Our resources are tested and proven and do make a difference.
• Rich tasks are suitable for learners of all ages and abilities.

I found several items in which sand cropped up (well, of course I would - as any reader of this blog is well-aware, the stuff is everywhere), but the puzzle caught my eye. It's geared towards kids in the 5-10 age group, but I'll readily admit that it took me a couple of minutes. And the interesting thing is that, if you go on the solution page, there are three different (but clearly related) methods of achieving what's needed.

So, this post is titled "Sand Puzzles #1" - anyone want to contribute number 2?

[Sandglasses image borrowed, with appreciation, from La Crosse McCormick, "Manufacturers of Fine Timepieces"]