A truly unique environment
A crescent shape can be made out from the sky corresponding to the side of the Aa Valley and the plateau that rises above it from Helfaut to Racquinghem. This curve, ten kilometres long and one to two kilometres wide, separates the Lys Valley and the Aa Valley that it overhangs. The composition of the soil (chalky at the base of the plateau and acid at the highest point), the relief, and the presence of underground water are very diverse and complex in this relatively small area. All of these factors have created varied and quite remarkable vegetation featuring woods, grassland, and heathland. There are no other examples of this type of natural environment north of Paris.
The heathland plateau was awarded the status of Zone Naturelle d’Intérêt Écologique, Faunistique et Floristique [Natural Area of Importance for Ecology, Fauna and Flora] (ZNIEFF) in the eighties and a “Réserve Naturelle volontaire” (Voluntary Nature Reserve) then Regional Nature Reserve in 2009. 500 species of plants and 450 different types of mushrooms can be found on this plateau. Ponds and man-made lakes are home to specific aquatic vegetation such as pondweed. This whole environmental mosaic combined with the presence of bunkers forms a choice habitat for rare or threatened species. Various types of bats have settled here including the pond bat (considered to be the rarest type of bat in France), a hundred species of birds thirty of which 30 are threatened such as common linnet, 13 species of amphibians and reptiles including the European tree frog and the northern crested newt as well as almost 500 species of insects including five rare types of butterfly and three types of dragonfly threatened.
From west to east, the heathland provides a variety of landscapes. In Helfaut and Wizerne, on the two facets of the Regional Nature Reserve can be easily made out. Chalk dominates at the base of the plateau with plants associated with it such as the fragrant orchid. “La coupole” can be found underneath this chalk. The presence of this blockhouse led to very heavy bombing which in turn created ponds and depressions on this site. In Blendecques, since the end of pastoralism (moving herds to new pastures), the plateau has gradually been covered with birches again. There is very little heather moorland remaining, lost between the ponds and trees. The work and management undertaken by Eden 62 is helping restore this heathland and rediscover these landscapes and flora once a major feature of this area. A little further east, in the Heuringhem area, in a locality called “le bibrou”, grassy meadows stretch out endlessly punctuated only by common gorse. This plant whose flowers give off the scent of coconut every spring quickly regained control of this meadow as soon as horses and cows – here most of the year – have moved on. The largest wooded area is situated in Racquinghem and Wardrecques. However, some clearings are home to the petty whin, a discrete thorny plant protected in our region.
A strategic headland
The strategic position of the “plateau des Landes de Blendecques “in Heuringhem, viewpoint of the River Aa and the Audomarois area has resulted in this being, for many centuries, a key strategic site for the different generations of the French army who set up camp there and undertake military exercises. “La Colonne du Duc d'Orléans” (The Duke of Orleans Column) bears witness to this period when several thousand soldiers were stationed in this location. If you take your time to hunt down the best position the views of the Aa Valley et Saint-Omer are breathtaking. With regard to fragile natural environments, the whole “plateau des lands” nature reserve is managed and enhanced by the Department through Eden62, a body run by the General Council and local Municipalities.