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?]