Les Blanches Banques

Les Blanche BanquesBlanche Banques June 2012. Photo by HGYoungThe sand dunes at the southern end of St Ouen’s Bay at Les Blanche Banques are one of the most important natural sites in the Channel Islands. This dune system, however, is going through a natural process of succession towards scrub/woodland, a process that has been accelerated over the last 60 years due to the construction of the sea wall and the subsequent stabilisation of the dunes. The site is visited by many people every day of the year and must be managed sensitively. 

Rabbit grazing. St Ouen's Bay. Photo by HGYoung The early successional short turf grassland supports a high diversity of plant species, some of which are very rare on a local and national scale (Dunes). This type of grassland is largely maintained by grazing animals, without which the habitat goes through the process of succession to rough grassland, scrub, and eventually woodland. Currently it is only wild rabbits Oryctolagus cuniculus that graze the vegetation: grazing by livestock ceased approximately 30 years ago and although rabbits have maintained areas of short turf grassland, many other areas have been lost to rank grassland and scrub Les Blanche Banques. Photo by Tim Ransomwhich is now beginning to dominate the site. Although these taller grasses and scrub are important habitats on the site for many species, their extent has become too high to the detriment of habitats earlier on in the successional chain.

Higher up the dunes at Mont a la Brune the vegetation structure and composition have been rapidly changing from grassland towards a scrub community with gorse, holm oak, blackthorn, bramble and bracken on its way to a scrub/woodland community.

Birds and other wildlife

Les Blanche Banques. Photo by Henry GlynnOver 400 plant species has been recorded on Les Blanches Banques. Impressively, 55% of the species typical of dune habitats in the whole of the British Isles are represented at this one site: 70% of those species only found in similar habitat in South West England. Seventeen vascular plant species listed in the British Red Data Book occur on the dune system, among them the lizard orchid Himantoglossum hircinum, sand crocus Romulea columnae, small hare’s-ear Bupleurum baldense and childing pink Petrorlzagia naneuilii. Many other locally rare plant species are found here including Nottingham catchfly Silene nutans, purple viper’s bugloss Echium plantagineum, sea-stock Matthiola sinuate, dwarf pansy Viola kitaibeliana, green-winged orchid Anacamptis morio and early purple orchid Orchis mascula.

The species-rich dune grasslands support a very high invertebrate diversity and there are many rare species including 29 British RDB species, a further 26 which do not occur or are now extinct in Britain and an additional 63 Nationally Scarce species. One IUCN RDB species, a wood ant Formica pratensis, now extinct in Britain, is among these species. Rare invertebrates such as the blue winged grasshopper Oedipoda caerulescens and bloody-nosed beetle Timarcha tenebricosa can be found here, as well as many butterflies which can often be seen in abundance on a hot summer day.

Sand martin at Mont a la Brune. Photo by Mick DrydenThe dunes are very important too for sand martin Riparia riparia (the Channel Islands’ largest colony is in the Mont a la Brune sandpits), wheatear Oenanthe oenanthe, skylark Alauda arvensis, meadow pipit Anthus pratensis, stonechat Saxicola rubecula and linnet Carduelis cannabina. Marsh harrier Circus aeruginosus regularly hunt over the dunes and nest close by at St Ouen’s Pond. Common toad Bufo bufo, green lizard Lacerta bilineata and grass snake Natrix natrix may be found at suitable spots.

Future management

Blanche Banques June 2012. Photo by HGYoungSand dunes are typically mobile, coastal habitats, with sand and salt being blown over the area by the prevailing wind and storms. This results in a unique flora, with only specialised plant species adapted to these extreme conditions of exposure, drought and salt being able to grow here. Since the construction of the sea wall, however, Les Blanches Banques has become a ‘closed’ sand dune system, with little sand being blown over the site. This has led to the dunes becoming stabilised, and has allowed different vegetation to grow and establish on the site. The area now has to be managed and monitored, to ensure that the dune vegetation is not lost completely. Current Blanche Banques June 2012. Photo by HGYoungmanagement includes the control of erosion and the loss of sand from these now stable dunes. The erection of fencing to catch sand and rebuild worn areas is a successful method. However, dune systems are inherently fragile and are very easily damaged by intensive human activities. Frequent patrols of Les Blanches Banques are undertaken by the warden of the site to collect litter, check for damage and monitor developments in the flora and fauna of the site. 

Proposed management of Les Blanche Banques includes:

  • Reduction of rank grassland and scrub in order to return these habitats to an earlier stage of succession;
  • Re-establishment of good quality grassland at Mont a la Brune through introducing management and grazing to the area;
  • Reduction of holm oak through selective felling and coppicing.