Zumaia » Location » Natural surroundings » The dune and salt marshes of Santiago



Santiago dune

The Urola river, has its source in the foothills of the Aitzgorri mountain range, and after nearly 60 km it ends at Zumaia after meandering in wide curves from neighbouring Iraeta. Where it meets the sea, on the right-hand side, the Urola forms an extensive bar of sand and mud in which two important coastal ecosystems have developed. To the north, opposite the Bay of Biscay, the dunes, and under cover of the bay, the salt marshes.

The geological materials that appear here include periods from the Upper Cretaceous, with limestone and marl, to the Lower Eocene, formed by sandy, marly clay and limestone. The transition from the Cretaceous period to the Tertiary shows limestone and marl with reddish layers, demonstrating iron oxide sedimentation.

On the substratum of limestone and marl from the Upper Cretaceous period, is seated the bar of sand and marl, of recent formation during the Quaternary. This sediment forms the beach and salt marsh, up to 30m deep in places.



Morning glory Calystegia soldanella)

Flora and Fauna of the beach and salt marsh

The beach and salt marsh display diverse vegetation according to the similarly diverse environmental conditions on the sands of the Santiago dune fields and in the gardens of Zuloaga House; which occupy the mud plains where the salt marsh has developed.

The beach (Dune)



Santiago Beach

In the upper part of Santiago beach, the vegetation is distributed in bands depending on its proximity to the sea. The influence of the sea, its salts and the wind have a strongly drying effect. The sandy ground, which absorbs the water very quickly, worsens the environmental dryness even more.

The plants that live on the border between the beach and the dune continuously struggle for space with the tide and the wind. The vegetation layer is shallow, normally composed of annual and quick-growing plants, which advance bravely towards the sea if the conditions are conducive.

A little farther off, small mounds of mobile dunes appear where sand, carried by the waves and the wind, is deposited - and also kept in continual motion. Here perennial plants grow, which develop long runners to attach themselves to the sand.

After these mounds, the so-called grey dunes develop, more stable and with a denser layer of vegetation. The sea is farther away and rain drags the salts to lower layers. The patches of running or creeping plants, the groups of annual plants, the naked surfaces and the marine pines form pretty mosaics lined by several footpaths.

The zone adjacent to the Zuloaga property limits is almost completely free of marine influence and there diverse scrubs grow, including some trees.



Sea rocket

The expansion of the sandy ground in Santiago has been reduced (3 hectares) and is subjected to strong recreational pressure, evidenced by the invasion of alien species of plants into the ecosystem. Nevertheless, its floral richness is remarkable; with up to 49 significant species being observed, among them several species of fungi.

In the gardens of the Zuloaga House/Museum, there are trees (mainly pines and cypresses), and in several places dune areas in very good state of conservation have been maintained. The fauna in the sandy area is composed fundamentally of invertebrates, of which the most common groups are insects, spiders and gastropods.

A long time ago, the green lizard was abundant, and small birds that make their nests in the woods or stop to rest as they migrate are frequent.

The salt marsh



The salt marsh, from the dockyards

The salt marsh is formed on a flat terrain with deposits of fine sediment throughout several kilometres in the Urola estuary. It is a selective atmosphere, with a high turbidity of water, due to the material in suspension coming from the river and the sea, which is why almost all the light is quickly absorbed.

The influence of the tides determines the installation of a very characteristic and specialised vegetation that appears in bands according to its tolerance to remaining submerged. Thus, at the lowest level, on a soft and barely solid substratum, only green seaweed is observed, which can survive well for long periods covered by the tide.

On the surfaces flooded by moderately high tides, in the first place there appear extensive grassy areas, which attach and raise the substratum with their roots, colonising the mud. This allows other plants, normally less able to prosper in these tidal areas, to establish themselves.



Mallards

On the highest substratum there is a third strip of vegetation, formed by plants typical of salt marshes, which occupy a very humid zone, rich in salts and nutrients of terrestrial origin, contributed by the river. The vegetation is dominated by salt-resistant plants and their composition varies: the most tolerant being located near the sea, and the most sensitive farther away.

At the foot of the slope of the road, where the tide only occasionally reaches, there is fresh water contributed by a stream, appearing in a zone with rushes and reeds.

The Urola estuary has two intimately related zones for birdlife: the area of Santiago and the surroundings of Bedua. Up to 100 birds related to the salt marsh have collected there.



Sea purslane

The periods with a greater presence of birds coincide with the great migrations. The spring period is the one in which the greatest number of birds are observed in the estuary, but it is during the autumn when the birds that visit stay for longer. Common then are the flocks of estuary birds like the sandpiper, lapwing, plover, godwit or redshank.

Swimming ducks are scarce, in general. However, usually observed, among others, are the mallard, the shoveler, etc. There are also many spectacular - and unfortunately very threatened - birds too, like the spoonbill, the barnacle goose or the purple heron.



Black-winged stilts

Another highlight every year is the appearance of a very rare bird of prey, the osprey, which usually stays in the area of Bedua and now and again looks for food in the Santiago salt marsh. During the winter the birdlife diminishes; the birds that remain here during this period are relatively common like the herring gull, the black-headed gull and yellow-legged gull, the common sandpiper, the ringed plover and the cormorant. Other common birds in the estuary are the little egret and the grey heron, whose main colony in wintertime in Guipuzkoa is located in Bedua.

Species, that during the winter are located in the open sea and that during hard seasons find it very difficult, look for refuge in the estuary.

In these cases, the Urola estuary is visited by birds like the arctic skua, the common scoter, the razorbill or the guillemot.

During the summer there are few species in the salt marsh; the pied wagtail and grey wagtail are observed, the common sandpiper, immature yellow-legged gulls and black-headed gulls, etc. Two nesting species stand out: the mallard, which usually rears in the gardens of Zuloaga House/Museum and the little ringed plover that does so in the zone of Bedua.