Sand dune - Country Report, Portugal
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This article on the sand dunes of Portugal, is a revised country report from the 'Sand Dune Inventory of Europe' (Doody ed. 1991) [1]. The 1991 inventory was prepared under the umbrella of the European Union for Dune Conservation [EUDC]. The original inventory was presented to the European Coastal Conservation Conference, held in the Netherlands in November 1991. It attempted to provide a description of the sand dune vegetation, sites and conservation issues throughout Europe including Scandinavia, the Atlantic coast and in the Mediterranean.
An overview article on the distribution of European sand dunes provides links to the other European country reports. These represent chapters from updated individual country reports included in the revised, 2nd Edition of the 'Sand Dune Inventory of Europe' prepared for the International Sand Dune Conference “Changing Perspectives in Coastal Dune Management”, held from the 31st March - 3rd April 2008, in Liverpool, UK (Doody ed. 2008)[2].
Status: Original authors: H.W.J. van Dijk & R. Tekke, original text with minor revisions by Francisco Taveira Pinto 2008; additional information Bird (The World’s Coast: Online)
Contents
Introduction
The Portuguese coastline is approximately 648km long and runs in a north-south and east-west direction. The coast is largely sandy, and includes many sand dunes and marshes. However, especially in the western part of the Algarve and along the south east coast, there are large stretches of cliffs and offshore rocky islands. A number of major estuaries break the coastline and in most of these, sand dunes occur.
Distribution and type of dune
The availability of material from fluvial sources along much of the coastline of Portugal, in combination with the strong erosive action and longshore drift, define a rather large sediment transport system. As a result, 60% of the coastline has sand dune formations, which are nowadays mostly deflating (Martins 1989). Most Portuguese dune formations consist of parabolic dunes, especially in the west. However, the dune systems can be rather complex, containing different geomorphological types extending from a few metres to 5 or 6km inland.
The coast south to Porto (Oporto) is low-lying, with sandy beaches and low dunes. At Esposende grassy dunes back a sandy beach, Praia de Suave Mar, north of the River Cavado. To the south of the River Douro, the coast is low and sandy, with coalescent spits forming barriers, capped by coastal dunes. The barriers are interrupted by an artificial entrance, bordered by protruding breakwaters, to the Ria de Aveiro, and sand drifting southward has accumulated as a wide beach with dunes north of the breakwaters, while to the south the beach at Praia de Barra is narrow and the backshore dunes eroded. The largest coastal sand dune systems are located along the north to mid-west part of the coastline. The major sites 1-12 are composed of unconsolidated dunes (Pereira & Coirria 1985).
Those to the west and south west of Lisboa are consolidated. On the coast to the south, the dune fringe has retreated, as at Praia de Vagueira and there are several seaside resorts, some with concrete esplanades built over the dunes, as at Praia de Mira. Beyond the end of the Ria da Costa Nova the dune fringe widens, and the dune vegetation is sparse, as at Praia de Tocha. The dunes fade out as the sandy beach ends at Cape Mondego. South of Figuera da Foz the coast fringes a sandy plain with extensive dunes, interrupted by a limestone promontory at Pedrogão. Concha de São Martinho do Porto is an oval-shaped tidal lagoon behind a gap in a coastal ridge, and dunes on the inner shore have been stabilised by black hessian sheets.
Cape Carvoeiro is a large tombolo, with a dune-fringed sandy isthmus leading out to Peniche. South of the River Tagus there are dunes behind sandy beaches on the eroding Costa da Caparita and along the curving coast south of Setúbal, but beyond Sines the coast is generally cliffed, and dunes occur only locally. The large dune area of Costa da Caparica also shows many mobile dune features. In the south west, the dune systems, particularly those included in site 21, are scattered and small. They include climbing dunes, which have developed, on the cliff slopes.
On the south coast, east of Cape St Vincent, cliffs give place to sandy beaches at Quarteira and dune-capped barriers enclosing lagoons and salt marshes extend past the cuspate foreland of Santa Maria to the Spanish border at the mouth of the Guadiana River. In the south (Algarve area), the coast west of Faro is mainly rocky but sandy beaches and some small dunes, such as site 22, occur locally. Between Faro and the Spanish border, there is a shallow sea bordered by sandy islands. On these islands large beaches, dunes and marsh areas occur; the mobile dunes here are rather low.
The coasts of the larger Portuguese islands (Azores and Madeira) also include dunes but these are not covered in this inventory.
Vegetation
Strandline
Cakile maritima and Salsola kali dominate the strandline vegetation. In Portugal, a transition between Atlantic and Mediterranean communities occurs and this transition is revealed by the presence of the Atlantic species Honckenya peploides along the northern coast and by the Mediterranean species Sporolopus pungens along the southern coast.
Foredune
Dune vegetation on the Atlantic coast of Northern Portugal includes a higher beach and embryonic dune. These are usually colonised by low-coverage and species poor communities. The foredune zone has plant communities, characterised by Elytrigia juncea, Eryngium maritimum and (sometimes) Euphorbia paralias. In this zone, a transition from Atlantic to Mediterranean communities can also be observed where Elytrigia juncea ssp. boreali-atlanticus is present in the north with Elytrigia juncea ssp. farctus in the south.
Yellow dune
The zone immediately behind the foredune consists of transverse dunes. The secondary dune is typically colonised, by communities of perennial herbaceous plants and small shrubs. These include vegetation dominated by Ammophila arenaria ssp. arundinacea, the main dune building species, with Othanthus maritimus, Calystegia soldanella, Medicago marina and Artemisia campestris ssp. maritima. The latter is a species, which is characteristic for the southern part of the Atlantic seashore of Europe. The vegetation also includes several endemic species such as Iberidetum procumbentis (Honrado et al. 2002).
Dune grassland
Plant communities in which Corema album is the dominant species cover the stabilised dunes (including grey and green dunes). If degraded, mainly by over grazing, these communities show high occurrence of Stauracanthus gelstoides. In the stabilised dunes south of the Tagus River another important plant community, with Thymus carouses present as a major species, occurs. A Thymus carnosus and Crucianella maritima community in the southwest replace this Thymus carouses community.
Woodland
Woodland is common in the stabilised dunes, in the climbing dunes and in the inner dune ridges of other dune types. It is mainly dominated by Pinus pinaster (sometimes P. pinea), Juniperus phoenicea and Quercus spp. In the northern and mid part of the coastline several introduced Acacia spp. from Australia play a local, but increasingly important role in the development of dune scrub and woodland.
Many sand dunes are planted with pine forest to help stabilise them. Site 10, Dunes and Pinhal de Leiria is one such. There are also some large areas of ‘fossil dunes’ deposited during the Pleistocene Period and during the ‘Little Ice-Age’ of the Holocene. These are particularly extensive near Espinho, to the north of Porto.
Important sites
[[Image: Table.jpeg|thumb|right|350px|Figure: List of important sand dunes sites in Finland.
Conservation
Additional information
Web sites:
References
- ↑ Doody, J.P., ed., 1991. Sand Dune Inventory of Europe. Peterborough, Joint Nature Conservation Committee/European Union for Coastal Conservation.
- ↑ Doody, J.P., ed. 2008. Sand Dune Inventory of Europe, 2nd Edition. National Coastal Consultants and EUCC - The Coastal Union, in association with the IGU Coastal Commission.
See also
- Sand Dunes in Europe
- Articles on sand dunes on Wikpedia
- European Sand Dune Distribution
- Sand dune types - Europe
Please note that others may also have edited the contents of this article.
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