The mobile nature of shingle means that many of the world's shingle features are largely bare of vegetation.
Shingle features are rarely stable in the long-term, being transient on a geological time scale. Most shingle beaches are within reach of storm waves so much of the vegetation is restricted to temporary and annual strand-line communities.
Shingle structures stable enough to support perennial vegetation are rare even in the Britain, which holds approximately one third of all the vegetated shingle in Europe (4-5000ha). In Suffolk there are 859 ha of vegetated shingle representing approximately 20% of the national resource. It is of note therefore that Orford Ness is the largest vegetated shingle spit in Europe and second largest but the best preserved area of vegetated shingle in Britain at 570ha. (Dungeness being the largest at over 2000ha)
The ridges and valleys have been deposited over many centuries by the action of the sea, in particular by longshore drift (the process of strong tidal currents moving material along the shore, in this case, in a mainly southerly direction) and plunging wave patterns. The ridges have become a visual record of the evolution of this complex landform with each ridge showing the position of an ancient shoreline. However, unlike the growth rings of a tree, shingle ridges do not necessarily show a progressive sequence of time. In many places an older series of ridges has been destroyed and replaced by a new series. So the age of the formation of Orford Ness still confounds the experts.
Colonisation of shingle is dependant on three main factors – degree of disturbance and mobility of shingle due to factors such as wave action; presence or absence of ‘fines’ in the shingle matrix; and the availability of moisture. Shingle ridges are formed by wave action (in particular storm waves) against a beach and as the shingle is laid down it has been naturally sorted and graded in size, with the larger stones lying in the valleys and the smaller ones on top of the ridges.
The finer (<5mm) fraction on the ridge improves seed and water retention, and although not essential allows some organic debris to be trapped and held. The presence of the 'fines' is thus crucial to the germination, establishment and survival of shingle plants.
The result of this colonisation is the distinctive strips of vegetated shingle for which Orford Ness is famous. It has highly specialised and important flora communities which includes significant plants, for example the nationally scarce Sea pea (Lathyrus japonicus), which is particularly mentioned in the European Union Special Area for Conservation (SAC) designation, and grows predominately along the drift line.
Shingle features are under increasing threat from development and gravel extraction as well as from ‘coastal squeeze’ in the face of rising sea levels and coastal erosion. Increasing use of coastal areas for leisure purposes and the consequent damage and disturbance is also creating a marked increase in the degradation of the local, national and thus global coastal vegetated shingle resource.
Coastal vegetated shingle habitats are extremely fragile; the damaging effects of access on foot, and particularly by vehicles have degraded many areas on the Ness, with loss of vegetation. The vegetation communities depend on the matrix of shingle, with an amount of finer materials mixed in with the coarser shingle, and on the hydrological regime. The causes include military use (now ceased), vehicle and pedestrian access to beaches by fishermen, and recreational use. Such disturbance can also have detrimental effects on breeding, feeding and roosting bird populations. The main potential threats to birds breeding on coastal shingle sites are probably ground predators and disturbance by humans. For example ‘loose’ colonies of Little tern are under severe pressure on Orford Ness from disturbance by humans, ground predators and but also in some cases from very high tides.
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