The importance of aeolian deposition is clearly shown by the size and bulk of coastal dunes. Sand dunes occur where there is a large supply of sand, a wind to move it, and a place in which it can accumulate. A dune classification is presented which takes into account the origin, internal geometry and surface geomorphology of coastal dunes. Since the main element that distinguishes coastal dunes from desert dunes is vegetation, the relative amount of vegetation may be used as a typology. Four dune types are distinguished: vegetated dunes, parabolic dunes, medanos (i.e. large sand hills devoid of vegetation), and artificially-inseminated dunes. Vegetated and medano dunes are the end members, with parabolic dunes in between. Parabolic dunes are “anchored” by vegetation, but the centre of the dunes has migrated in the down-wind direction. The artificially-inseminated dunes are formed by vegetation plantings, fencing, or other artificial means, but with natural sand accumulation around these obstacles. These now account for a very substantial portion of the world's coastal dunes.

The role of wind and its relation to the internal geometry (i.e. cross-bed dip and direction) are discussed in some detail, with examples from Brazil, U.S. east and south coasts, Israel and China. Differences in these characteristics are detailed, and related to the different modes of formation of the four dune types.

The role of the wind in transporting and depositing sand in coastal areas is being quantified through both wind tunnel and field transport measurements. An example from a field study along the coast of Israel illustrates the differences between desert and coastal dune transport, where the role of vegetation and beach topography must be taken into account. From the Israeli study, and others, it appears that transport in coastal dunes is reduced by one-third to one-half of that in deserts, due to these factors.

Coastal dunes provide a useful, and often necessary, buffer against storm waves and the presently rising sea level. They form primarily through vertical sand accretion trapped by the sensitive dune vegetation. Provided that sufficient space exists between the high tide line and developed areas, planned dunes can be easily formed with the aid of plantings and fencing.

With the gradation of intensities of environmental factors from the strand-line to stable inland areas, coastal dunes show many ecological phenomena especially clearly. These are reviewed broadly, with some emphasis on topics on which important advances are being made. The nutrient status of dune soil and changes with time are shown with reference to several dune systems. Changes in major nutrients are given for Braunton Burrows, north Devon, where the influence of nitrogen fixation by Lotus corniculatus is illustrated. The effects of sand burial on plants are considered, and details given of the root systems of vigorous and relict marram; factors which may affect its decline in vigour are reviewed. Also discussed is the likely significance of nematodes in the decline of Hippophaë rhamnoides. Reasons for the richness of the dune flora are considered and also some autecological studies. At the physiological level, reference is made to the water relations of plants and at the biochemical level to the occurrence and possible ecological importance of stress metabolites. Life strategies, phenology, survivorship, competition and the population ecology of dune plants are reviewed and also the interaction of ragwort (Senecio jacobaea) and cinnabar moth (Tyria jacobaeae). The population genetics of dune plants is illustrated by reference to Festuca rubra and Ammophila arenaria and of animals to Cepaea nemoralis.

The abundance and ecological relationships of the invertebrate fauna are exemplified by surveys at Spurn Point, extensive investigations on spiders and the influence of marram on arthropod communities. The ecology of the natterjack load is considered in relation to conservation and the effects of large animal grazers in relation to the diversity of vegetation.

A strategy for predicting topographical change in dune fields is presented by way of a logic chart. The primary underlying physical requirements of the calculation are outlined. Most important are understanding of the dependency of sand transport on wind and of the wind structure on surface relief. Knowledge of the latter is still limited. Reference is also made to the role of vegetation in inhibiting transport and briefly of size re-sorting. Some evident research needs are extracted from this review.

The National Vegetation Classification has details of some 2000 samples of sand dune vegetation collected nationally. Analysis of these data has resulted in the recognition of about thirteen plant communities of the sand dune system. Details of these communities are presented, elaborating on their species composition, variability, ecological relationships and distribution. As might be expected, the major direction of variation is from strandline, through the vegetation of active dunes, to the fixed dune grasslands, heath and scrub. The precise pattern is affected by the calcium status of the dune and by its geographic location. The vegetation of dune slacks is also dependent on the calcium status of the sand, as well as the amount and persistence of standing water. Superimposed on this natural pattern of variation is the use of dune systems by the grazing of domestic animals as seen on the machair of the Hebrides in particular.

The herbaceous vegetation of sand dunes is quite strongly influenced by a number of different grazing animals, principally vertebrates. Between 1985 and 1987 forty-eight dune sites were visited and studied, information being recorded on the vegetation and grazing status of 777 quadrats.

The results of the survey confirm that the dominant grazing animal in British sand dunes is the rabbit. Over 70% of the quadrats are regarded as being rabbit-grazed directly and over 98% of the dune sites sampled appeared to be affected by rabbit grazing to some extent. Just over a third of the sites were grazed by cattle and a similar proportion by sheep; generally it was either cattle or sheep although five sites were grazed by both. There was only one site significantly grazed by ponies although a number of other sites were grazed occasionally by passing ponies.

The intensity of grazing was very variable. Out of the forty-eight sites, three were regarded as being ungrazed and a further ten only lightly grazed, while nine sites were considered to be heavily grazed. However the remaining twenty-six sites were recognised as being intermediate only to the extent of not being obviously overgrazed or undergrazed. It was further recognised that the present state of the vegetation tended to reflect the grazing management in the recent past rather than current practice. A change in the grazing management often took many years to effect a permanent change in the vegetation.

The grazing requirements to promote species diversity are very different for the different habitat types. In the yellow dunes the plant community is open with bare ground for colonisation and plant competition is not intense. There is thus little need for the control of plant growth by grazing.

Dune grassland, in the narrow sense, needs to be grazed to maintain plant species diversity. The purpose of grazing is to remove prolific growth from the most vigorously growing plants to reduce competition. Lower grazing intensities are needed for all the year round grazing than when grazing is first applied to an area or is a permanent measure for limited periods of the year only.

Dune slacks are generally best grazed by cattle and, with the higher soil moisture, grazing intensities can be higher than those applied to dune grassland. Excessive grazing is likely to cause serious damage to both the soil and the vegetation, especially in the wetter areas.

Dune heath vegetation has a low productivity and its own special management problems. It needs to be grazed (or cut or burnt) to maintain the internal mosaic by the successful regeneration of the main species, but too much grazing will lead to conversion to a species-poor acid grassland.

The extent of occurrence, the form and the function of mycorrhizal infection are shown to change with successional development across coastal sand dune systems. The interrelationships between these changes and the prevailing physico-chemical conditions are explored and clear patterns are recognised in terms of both type and function of the infection. The periodically disturbed and nutritionally enriched high tide line is colonised by non-mycorrhizal ruderal species. There follows a sequence of plant communities, each characterised by the presence of a dominant mycorrhizal type and a distinctive nutritional limitation. In the foredunes, pioneer grasses are normally infected with vesicular-arbuscular (VA) mycorrhizal fungi. Plants such as Ammophila, Leymus and Uniola, all of which have extensive root systems, appear, when fully grown, to be only facultatively mycorrhizal. However, experimental evidence suggests that infection is important for the early growth of such plants and it is suggested that in these, as in many other dune species, mycorrhizas may be essential at critical stages in the life cycle, most notably during the phase of seedling establishment. Here, phosphorus (P) is the most important growth-limiting nutrient. The extensive mycelial network of VA hyphae not only facilitates capture of this element but also provides the aggregation of sand grains necessary for dune stabilisation. In semi-fixed dune pastures, as sand inputs are reduced, productivities are low and species diversity increased. Phosphate limitation persists and the majority of the characteristic species show VA infection. Experimental studies using microcosms of dune sand containing an assemblage of species typical of such communities suggest that the maintenance of the species richness is dependent upon mycorrhizal fungi which produce a large absorptive mycelial network into which the roots of germinating seedlings become incorporated as they are infected. Accumulation of organic matter in dune-slacks leads to reduction of pH. Nitrification is inhibited, ammonium becomes the major mineral nitrogen (N) source and N replaces P as the key growth-limiting element. Here plants with ecto-mycorrhizal infection predominate. Salix repens produces a shrub layer enriched with litter in which a guild of species interconnected by a common mycorrhizal mycelium occurs. The functional basis of this guild structure is explored, the ability of some of its mycorrhizal fungi to mobilise nutrients from organic macro-molecules being seen as a vital attribute. Where organic matter accumulation and base depletion are most strongly developed in the oldest parts of the succession, plants with ericoid mycorrhizas become important. The ability of their mycorrhizal fungi to liberate N and P from acidic organic complexes, as well as to assimilate or exclude, and hence detoxify, organic acids and metal ions facilitates vigorous growth of ericaceous species in soil conditions which are inimical to plants important earlier in the succession. Since the attributes of each mycorrhizal type are relevant to a specific suite of edaphic properties the formation of appropriate symbiotic associations is likely to be a prerequisite for successional change. It is concluded that mutualism contributes significantly to fitness in the sand dune ecosystems, the further understanding of which will be dependent upon more effective collaboration between the microbiological and ecological disciplines.

Our knowledge of the macrofungi of British sand dune systems is outlined and similarities and differences are discussed, based both on intensive studies and scattered observations, particularly in Scotland and Wales. Comparisons are made with European sand dune communities, and much wider observations from as far afield as N.E. Australia and North America are presented. Several records new to Britain are documented.

The paper discusses limits under which flux-gradient relationships derived for horizontal homogeneous terrain can be applied to aeolian transport over non-uniform terrain with coastal dunes. For flat sandy beaches the roughness change upstream of the beach-dune boundary can be expected to be small. For horizontal beaches that are some hundred metres wide and where the length scale of the horizontal heterogeneities does not exceed some tens of metres, consistent surface stress and aerodynamical roughness values may be deduced from the wind-speed profile.

Slope effects will modify the air flow strongly as it crosses a dune ridge or escarpment. Recent developments in the theory of turbulent flow over hills are discussed in relation to common coastal dune terrain. The depth of the layer where the profile is in equilibrium with the underlying surface typically does not exceed a few tens of centimeters. This strongly restricts our ability to derive reliable values for roughness and surface stress from the wind profile.

Experimental studies at two coastal dunes in Denmark indicate that it is often difficult to obtain a good upwind reference for the flow. Analysis with a numerical model, set up for one of the sites, suggests that information about the flow and the value of experimental data may be improved when these can be both related to and supported by numerical calculations.

In the last two decades both experimental and theoretical research in aeolian sediment transport has greatly enhanced our quantitative understanding of the saltation process. I emphasise the qualitative understanding of saltation that has emerged in part through development of a numerical model consisting of four subprocesses: (1) aerodynamic entrainment, (2) grain trajectories, (3) grain-bed impacts, and (4) momentum extraction from the wind. Each sub-model encapsulates the physics of the process, and is constrained, where necessary, by experimental data. When combined, the full model allows simulation of aeolian saltation from inception by aerodynamic entrainment to steady state. The results are encouraging, showing both qualitative and quantitative correspondence with wind tunnel measurements.

In an attempt to further the qualitative understanding of the problem, an analogy is proposed between the saltation population and a biological population, wherein both individual and collective properties are considered. Although at present these models lack the detail to treat the true complexity of the natural world – in particular the wetness of beach sands and the potential role of beach vegetation – they serve both to develop our intuition about the natural setting, and to guide future experimental efforts.

Sands are sorted by the actions of air and water. A mathematical–physical model for the ensuing spatial and temporal variations in the size distributions of the sand grains is outlined. A crucial element in aeolian sorting and transport of sand is the process that takes place when a saltating grain impinges on the sand surface. This raises the problem of describing the texture of sand surfaces. Some initial empirical and mathematical findings concerning this problem are discussed. A closely connected question is that of how the grains in a sand deposit are packed and how this relates to the size distribution. Voronoi tesselations in combination with random point processes seem to offer one useful approach to the question.

The evolution, ecological processes, aerodynamics, and morphology of incipient or new foredunes on the upper beach is reviewed. Four types of incipient foredunes may be distinguished, namely: type 1, those initiated by shadow dune formation within zones of discrete individual pioneer annuals (e.g. Cakile spp.), and perennials (e.g. Spinifex spp.; Ammophila spp.); type 2, those initiated by dunelet or hummock formation within discrete colonies of perennial grasses and herbs; type 3, those initiated by sand deposition within laterally extensive colonies of pioneer seedlings; and type 4, those initiated by sand deposition within a laterally extensive plant rhizome cover.

Type 1 dunes are dominated by high, local flow deceleration and 3-D flow separation. Shadow dunes form within and downwind of the discrete plants. If colonised by annual plants, invasion by perennial plants is necessary for survival. Later lateral plant spread and accretion produces hummocky terraces and ridges. Type 2 dunes (dunelets) are characterised by local landward flow deceleration and marginal high velocity side flows. Sand deposition results in the formation of low, discrete, semi-circular convex mounds (seedlings), or more elongate hummocks and mounds (rhizomes). Types 3 and 4 dunes are characterised by laterally extensive, often homogeneous vegetation canopies. High canopies display more rapid landward flow deceleration than low canopies, thus narrow, asymmetric ridges and longer convex ridges result respectively. High plant densities result in rapid down-canopy flow deceleration, maximum traction load retardation and the formation of narrow asymmetric ridges. Dune height decreases and dune length increases as plant densities decrease. Maximum deposition zones occur for each wind velocity range. Whether ramp, terrace or ridge morphologies are formed depends on mode of beach colonisation, plant density and distribution, sand volume, wind speed, and plant species type and morphology.

A range of variables which affect foredune morphology and evolution, including plant canopy density, height and distribution, wind velocity, and various ecological environmental processes are examined.

The principal types of stratification and some characteristic sedimentary sequences found in vegetated coastal dunes in Atlantic Canada are described. Four examples are selected to show a range of dune types and depositional settings. In each case the documentation and interpretation of the internal structure and stratification has made an important contribution to understanding the evolution of the dunes. Stratification and depositional models are presented for:

(1) a single, continuous, transgressive foredune ridge which maintains its form during transgression;

(2) a discontinuous transgressive foredune ridge, interrupted by washover passages;

(3) a “precipitation” dune, which buries an existing stable dune; and

(4) complex dunes produced by two or more phases of aeolian activity characterised by different plant associations.

In Dutch coastal dunes, geomorphological and geohydrological processes have been adversely affected by intensive utilisation of the dunes. In the past, wide-scale stabilisation, notably for reasons of coastal defence, stopped nearly all aeolian activity. Rejuvenation did not take place and succession to mature-type ecosystems increased. Artificial infiltration with eutrophic river water and extraction of groundwater for drinking water catchment modified the geohydrology of the wet-dune environment.

Today, actions are being taken to restore geomorphological and geohydrological processes. Managing authorities join forces with universities and policy makers to strike the right balance between conflicting interests. Applied research helps to develop management strategies.

Two types of research are discussed: (a) geomorphological work on the development of blow-outs; (b) geohydrological work on the development of dune slacks. Questions considered are: do blow-outs grow to an unlimited extent or do they have optimum size and shape corresponding to aerodynamic conditions? Are there natural stabilisation mechanisms for blow-outs? What is the ecological impact of drinking water catchment? Which aspects should be considered to restore the dune slack environment in catchment areas?

Our findings are that blow-outs in The Netherlands have an optimum length:width ratio of about 2 with a blow-out length varying between 20 and 30 m. After 10–15 years without artificial stabilisation measures, the areas studied present an average of about one blow-out per hectare. Natural stabilisation mechanisms include algae which colonise deflation sites inside the blow-out and low secondary dunes which develop at the immediate leeward side of the blow-out. Blow-outs situated at or near downhill slopes of 6–12° may easily extend into larger deflation surfaces. Water erosion, probably caused by the water-repellency of humus-rich top soil, often precedes wind erosion on south- and south-east oriented slopes.

Drinking water production caused dessiccation of dune slacks and the disappearance of associated vegetation. In areas where infiltration with river water from outside the dunes is also applied, inudation and eutrophication drastically changed the dune environment. Nitrophilous plants appeared, especialy along banks of infiltration ponds, but also in seepage ponds. The plant cover depends on nutrient concentration of the (infiltrated) groundwater but especially on the flux of the groundwater. A high rate of flux leads to high nutrient loads, encouraging the growth and eventually dominance of nitrophilous plants. Restoration of dune slacks depends on the quality and the flux of the groundwater, on the streamlines of the groundwater flow in the dune body in relation to the orientation of the seepage ponds, on the presence of peaty or clayey adsorptive layers in the subsoil and possibly also on the presence of a rainwater lens occurring on top of the infiltration water.

Six major oil and natural gas pipelines make landfalls on the coastline of north-east Scotland. Four land at St Fergus, one at Cruden Bay and one at Shandwick. The Cruden Bay line dates from 1973: at St Fergus landfalls were made in 1975, 1976 and 1984: and at Shandwick in 1979. With the exception of the Shandwick landfall, the pipelines cross relatively wide sandy beaches with associated dune ridges. All the pipelines were laid using a simple trenching technique whereby a beach trench was dug and a large V-shaped cut made through the main foredune ridge and interior backslope, inner dunes or slack environments. All these landforms were replaced quickly by backfilling. Thereafter, physical devices such as nets, brushwood, sand trapping fences and bitumen sprays ensured surface stability. Equally important was a replanting programme which had two main components: – hand-planted marram grass and agriculturally seeded grass mixtures. Topsoil was added, fertiliser was applied and other cultivation practices were used.

Since 1973, several surveys of the progress and success of these restoration procedures have been made. On the whole, landform stability has been very satisfactory. Re-vegetation has met with mixed success, especially with regard to those changes which could be described as the gradual re-invasion of natural or local plant associations to replace the artificially planted species. Various lengths of time have ensued, and in some examples the rate and pattern of re-vegetation have been examined by means of periodic sampling. This has made possible reasonable assessments of the influence of local environment factors on the ability of sown species to establish and create a sward, the extent to which they persist over a period of years, and the ability of native species from the neighbouring dune system to re-invade and compete successfully in the developing turf. Standard methods have been used for planting marram grass to stabilise the steeper seaward sand slopes, but these are reviewed in the light of results of recent experimental studies of various planting techniques. The possibilities for exploiting these findings in the rehabilitation of any future pipeline crossings of dunes are considered. Since slightly different re-vegetation procedures were adopted in the several dune crossings under review, it is also possible to comment on the optimum solutions to restoration problems of this kind which are associated with mature coastal sand dunes.

Sand dunes occur extensively around the coastline of Great Britain and in a wide variety of forms. Management for nature conservation is influenced by a long-term historical perspective which has led to a continued policy of protection. It has aimed firstly to prevent damaging developments such as building and orestry, and secondly to control excessive erosion brought about predominantly by man's own activities. However, an assessment of current nature conservation management problems suggests that at many sites in Great Britain over-stabilisation may be as much a problem as erosion. The implications for management in the face of other competing demands is discussed.

The first comparative study in Britain of the invertebrate fauna of a large number of coastal sites was carried out in Scotland in 1976/77. Fifty-eight sites were selected at fifty-four locations in four geographic areas: East Coast, Moray Firth, North & North-west Coast and the Outer Hebrides. Lepidoptera were collected in MV light traps, while Coleoptera, Araneae, Mollusca and Diplopoda were caught in pitfall traps. The results are analysed to show the relationships between the faunal elements of each region and how species distribution correlates with latitude and is affected by climate. Examples are given to illustrate the great range of distribution patterns of selected species in the five major invertebrate groups studied. Some priority areas for site conservation are listed and recommendations made for a different approach to dune management.

Coastal foredune management begins with an understanding of and appreciation for the dynamics of dune creation, development and decay. Sediment exchange between the dune and beach components of the total dune–beach profile is a necessary element in foredune creation and development. Foredune development is enhanced by a slightly negative total dune–beach budget. Foredune crestlines display alongshore periodicities in displacement that are related to beach processes. Effective management is based on the dimensions of the alongshore foredune variations and the retention of sediment in the migrating foredune system.