GENERAL FEATURES OF THE EUROPEAN COAST

The coastal area and marine waters of Europe are areas of great contrast.  The nature of the coastline is formed by a combination of factors which include physical factors like tide, currents and waves determining  the geomorphology, habitats and related biological characteristics influenced by sea level rise, climatic variation and human activities.
One of the purposes of this study was to determine the vulnerability of specific coastal landscape types and habitats in relation to the environmental impacts arising from a variety of socio-economic sectors.

 1. The Coastal Landscapes of the European Union

Coastal landscapes can be divided into two major groups which provide a useful distinction when considering coastal management and planning. The first consists of the “cliffed and rocky coasts”, the second can be described as “coastal plains”.   This is a commonly used distinction in international typologies.  More detailed distinctions can be made, but would be less relevant in determining vulnerability to environmental impacts.  The tidal range of coastal waters is another important factor in describing the nature of coastal landscapes, because it reflects the resilience of a particular coastal type. The more dynamic the system (e.g.  micro tidal), the more resilient the system is to a variety of environmental changes (including adverse impacts from development).  Table 1 shows the main tidal ranges along the coast of the European Union.
 
 

Table 1   Tidal Ranges and Their Occurrence

Type	Tidal Range		Regions
micro-tidal	< 1 m		Baltic and Mediterranean coasts
micro-tidal	1-2 m		North Sea coasts: Shetlands, western Denmark
meso-tidal	2-4 m		Atlantic and North Sea coasts
macro-tidal	> 4 m		Atlantic and North Sea coasts

 
 

1.1  Cliffed and Rocky Coasts
Cliffed and rocky coasts occur in both high and low relief areas where the underlying geological structures are relatively resistant to the erosive forces of  sea, rain and wind. They are mainly found along Atlantic coasts, in eastern Scotland as well as around the Mediterranean. In areas of high relief the landscape is often characterised by steep cliffs, rocky outcrops and deep, usually clear offshore marine waters with small embayments.  Although more mobile sedimentary systems (such as pocket beaches, dunes and shingle shores) may be present they are seldom extensive.

1.2  Coastal Plains
Primarily low relief areas with abundant sediment are found in most European regions.    Rivers and  erosion of glacial or other soft rock cliffs together with offshore marine sediment supply material for the growth of sometimes extensive sedimentary habitats, intertidal sand/mud flats and saltmarshes and onshore and offshore sand dunes and shingle structures.  Typical barrier islands and coastal plains as, for example, in the Wadden Sea are examples of sedimentation processes.

In the context of this report the gently sloping landscapes along many of the Baltic shores are also included in this group of coastal plains. It must be realised however that those of Sweden and Finland which are subject to isostatic uplift have a very different character compared to sedimentary systems.  In micro-tidal areas, storms and longshore drift provide the main driving forces for accretion and erosion.  Much of the available sediment is produced as a result of land erosion following deforestation, washed offshore from the hinterland.  Extensive sedimentary deltas may be formed, which may include wetlands, lagoons, saltmarshes and sand dunes.
 

2 Distribution of Natural Coastal Landscapes

The various landscape types, tidal ranges and some natural coastal habitats have been indicated in a map “Coastal Systems of  Europe”.

2.1  The north and west - a Predominately Cliffed Landscape
The more exposed rocky and cliffed coastlines extend from the north and west of Scotland, the west coast of Ireland, Wales and southwest England to northern France, the northwest of Spain and Portugal.  Throughout much of this zone the coast is characterised by a macro-tidal range which in the southwest of the UK is the second highest in the world (12m).

In the north where the land is still rising relative to sea level and the coastline is formed  from ancient rocks resistant to erosion, some of the most spectacular and remote cliffed landscapes occur.  These cliffs may have vertical or sloping rock faces and in exposed locations are often drenched in salt spray as the sea is driven onto the shore, especially where they face the full extent of the Atlantic Ocean in the Celtic Seas and the northern North Sea.  Indentations in the coast may occur as fjords (in high relief areas) where glaciers have worn away depressions in the rocky coastline, which have subsequently become flooded by the rising water following the end of the last glacial period, about 10,000 years ago.  Some of the sea lochs of western Scotland can be similarly classified.  They may contain important marine flora and fauna, have saltmarshes at the head of the fjord or loch and can be surrounded by steep sided wooded slopes.  Fjards occur in glaciated, low relief areas, such as western Scotland, eastern Denmark, and much of the Baltic coast northwards from southern Sweden.  They typically have associated islands which are highly indented (skerries) and result from the emergence of land following the last ice age.

Many cliffs, particularly the east-facing coasts of northeast Scotland and eastern Ireland, are only marginally exposed to the full power of the wind, breaking waves and salt spray.  The mainland west coast of Scotland is similarly sheltered by the Outer and Inner Hebrides.  Because of the close proximity to the rich waters of the Atlantic Ocean and the North Sea the steep cliffs often support large colonies of cliff nesting seabirds.

Further south, in the southern zones of the Celtic Seas including southwest Ireland, Wales and southwest England to southern Portugal, spectacular west-facing cliffs also occur.  In Spain and Portugal relative sea level change is due more to local isostatic change, to tectonic effects and/or human influences than the impact of glaciation.  The rocky shores and cliffs within this zone tend to be composed of younger rocks laid down under warm seas to form chalk and limestone.  These are less resistant than the harder rocks further north and in some areas rapid rates of erosion (1m or more per year) occur, as for example in the chalk cliffs of the Channel coast.  The coastlines of southwest England, northern France and northern Spain also include estuaries within the hard-rock dominated landscapes.  These occur as rias (river valleys drowned by the rising waters following the last glacial period) with typically narrow, steep, often wooded, valley sides.

2.2  Atlantic Coastal Plains
Also along the exposed west-facing “Atlantic” shores coastal plains with sedimentary habitats occur.  These may be relatively extensive as in the case of the lowland estuarine areas of Liverpool Bay and the Severn Estuary in western Great Britain or the Loire and Gironde in western France.  Western France also has one of the largest expanses of dunes anywhere in Europe at “Les Landes” in the south.  Here their development involves the progressive stabilisation of dune forms as the sand is blown inland and vegetation helps to create the more typical undulating dune landscapes.  Many dune systems have been stabilised and affronted.

2.3  The Coastal Plains of the Southern North Sea and Baltic Sea
The common feature of this geographical zone lies in the abundance of the sediment supply, much of it derived from the soft glacial material deposited during the various ice ages and especially at the end of the last glaciation.  As a result, soft eroding cliffs, sand dunes and saltmarshes are common terrestrial and tidal habitats whilst subtidal areas tend to be dominated by softer sediments on the sea bed.  The southern North Sea lies in an area of relatively high tidal range and along with the coast which borders the northeast Atlantic are classed as macro-tidal.  This situation favours the development of the typically estuarine coastline with abundant and extensive areas of tidal sand and mud flats, saltmarshes and sand dunes.  In addition, barrier islands, spits and bars are also common features.  The Baltic Sea by contrast is classed as micro-tidal.  In fact the tidal range here is extremely small, from 0.08 m to 0.18 m.  This has important consequences for the nature of the coastal landforms which occur in the area.

Estuaries and their associated sedimentary habitats occur around the whole European coastline, wherever there is a suitable source of material.  However, they find their best expression in the major sites of the southern North Sea.  Their complex and often highly productive mosaic of habitats can support large populations of migrating and wintering waterfowl, which is the most obvious manifestation of their biological interest.  These may include internationally recognised concentrations of wildfowl and waders which breed further north in the Arctic and elsewhere.  Especially important are the estuaries of southeast England, Zeeland and the Wadden Sea which may also include both abundant and rare species of birds, invertebrates and fish.  The surrounding habitats, including saltmarshes, sand dunes, shingle and coastal grazing marshes, are an integral part of the overall ecosystem.  These habitats are important in their own right for the specialist plants and animals which survive there and their high productivity which forms the basis for commercially exploitable species e.g. fish and shellfish.
Saltmarshes are especially important in the macro-tidal areas and are composed of sequences of communities tolerant of different degrees of submergence by the tide, which may develop into transitions to other, terrestrial vegetation. Transitions may be to reed swamp, sand dune, shingle, freshwater or woodland, which can be particularly rich in a wide variety of plants and animals.  This natural transition may be truncated by the construction of sea walls or other coastal defences, with the loss of this rich variety of wildlife.  In some areas where a saline influence continues landwards of sea walls on enclosed unimproved saltmarshes, coastal grazing marshes with brackish ditches may develop.

Sand and shingle beaches, sand dunes and shingle structures associated with these flat sedimentary landscapes may exist as part of an integrated coastal system, or as separa-te, sometimes large structures.  These include the major sand dunes of the coastlines of The Netherlands and Denmark, or the unique shingle foreland of Dungeness in southeast England.  Each habitat has its own group of coastal plants which are specially adapted to bring stability to the usually hostile environment. Afforestation with a variety of native and non-native pines in the north has reduced the open dune landscapes in many countries, notably Denmark where they were planted to aid sand stabilisation.

Sea level rise is of considerable importance throughout the region.  The combination of static or sinking shorelines (which result from the lowering of the land thought to have been pushed up to the south of the ice sheets during the period of maximum glaciation as the ice retreated) and rising sea levels results in relative sea level rise which may be on the order of 4-6 mm per year in some areas.  This tends to push coastal habitats to-wards the land.  Where this migration is restricted by rising landforms or artificial struc-tures built to defend the land from erosion and/or flooding then the coastal zone is pushed into an ever narrower strip causing a coastal squeeze.  This has important implications not only for the habitats but also the ability of the coastal landforms to provide a flexible response to storms and extreme tidal events which may have an impact on human use and infrastructure at the coastal margin.

2.4  The Mediterranean Sea
The two broad categories of coastal landscapes (high cliffs and low-lying flat land) are not mutually exclusive, nor restricted to particular geographical areas.  There are, for example extensive cliffs in the Mediterranean, and areas of coast with little sediment which correspond to the hard rock cliffed landscape described for the north and west.   These cliffs and more gently sloping rocky shores are often composed of various types of limestone which form the basis for the karst landscapes of the hinter-land. The combination of thin limestone soils, climate and the long history of grazing and burning of the natural vegetation has helped to create the low shrubby drought- and grazing-resistant vegetation which covers large areas of the coastline.

Deltas and narrow coastal plains, generally occupied by wetlands and lagoons, help to define the landscapes of the Mediterra-nean coasts.  These are present throughout the region and are most extensive in areas backed by mountains where major eroding catchments deliver large quantities of sand and silt to the coast.  Short torrents, without water during most of the year, are draining  enormous volumes of water  in response to heavy local rains, in very short periods. This causes floods which also enhance sedimentary processes.  This process combined with the small tidal range help to create some of the largest deltas in Europe: those of the Ebro, the Rhone (Camargue) and the Po. All of these have been modified in some way by human activity whether through changes to the cycle of deforestation in the hinterland, damming of rivers delivering the sediment or drainage and other activities in the deltas themselves.  The majority of the deltas both large and small are of considerable importance for both human use and wildlife, providing food and locations for urban and industrial development for the former, and migration, breeding and wintering areas for the latter.

The dunes associated with these sedimentary areas may also be extensive.  These often support a shrub vegetation similar to that of the hinterland.  Many large afforestations (e.g. with pines and Australian Eucalyptus) have reduced the area of natural dune landscapes.  The development of infrastructure associated with the growth of the tourist industry has also devastated many areas and has had a major impact on much of the landscape.

Offshore there are significant areas of hard rock substrates which support rich and varied benthic communities.  However, one of the most significant marine landscapes derives from the presence of extensive sea grass communities - notably Posidonia beds.  These play a vital role not only in the biodiversity of the seas but also as nurseries of many of the commercial fish stocks of the Mediterranean.
As with the lowland areas in the southern North Sea and the Baltic, relative sea level rise can have important implications for the future of the deltas of the Mediterranean.  However here the pattern of change is much more complicated with tectonic movements caused by a variety of influences (e.g. volcanic activity and earthquakes).  When this is coupled with human influences which exacerbate sea level rise, significant problems of erosion, salt water intrusion and flooding can occur.  These effects are especially important in the major deltas where a decrease in sediment availability and subsidence due to water abstraction or the sheer weight of infrastructure may be some of the factors which give rise to substantial problems of erosion and flooding as is being experienced in several of the major Mediterranean deltas.