Ebro Islands Wetland

The hydrogeomorphological evolution of L’Aubadera Island

L’Aubadera Island is one of the four islands in Móra d’Ebre: Subarrec Island, L’Aubadera Island, El Galatxo Island and El Vado de Vapor Island.  These river islands, formed by an accumulation of sediments (pebbles, gravel, sand and silt) carried by the river, are protected areas included in the Natura 2000 network. L’Aubadera Island, specifically, is in the Catalogue of Wetlands of Catalonia.

Before dams and reservoirs were built, the Ebro River’s dynamics were highly changeable in terms of flow and sediment transport. Floods could carry sediments that would erode both the riverbed and the riverbanks. At the same time, they prevented vegetation from becoming established there and compacting the soil, which meant that the anabranches remained open with constant circulation, depending on the flow.

When dams were built at both the source and the mouth of the Ebro River (between the 1940s and 1960s), the river and its dynamics were totally transformed.  Its flow was much more regulated and stable, without regenerative floods. As a result, riparian woodland vegetation was gradually consolidated in most of the areas adjacent to the river, like L’Aubadera Island. It is important to note that one of the functions of riparian woodland is stabilisation, which helps to prevent soil erosion in the event of a flood.

Historically, L’Aubadera has been popular with the people of Móra d’Ebre, who have used it for several purposes: livestock farming (as pasture); swimming; leisure, sports and cultural events; and for entertaining the youngest members of the town’s population.

In recent years, management and conservation measures have been introduced to protect L’Aubadera and other natural areas on the Ebro River in the town of Móra d’Ebre. These have included habitat restoration, riparian forest management and awareness-raising surrounding the importance of protecting these river ecosystems.

The hydrogeomorphological evolution of L’Aubadera Island is a complex process, influenced by natural and anthropogenic factors. Understanding this process is key in order to ensure sustainable management of natural resources and the conservation of the Ebro’s fluvial landscapes.

Riparian woodland in the L’Aubadera Island nature area

In the heart of the Ebro Islands nature area, L’Aubadera Island emerges as a natural, biodiverse oasis, with an extensive variety of habitats and species. This island, located near Móra d’Ebre, is living proof of the beauty and biological richness of riparian woodland.

Silver poplar (Populus alba): This deciduous species is one of the most common trees on L’Aubadera Island; in fact, the island’s name is derived from it (aube in Catalan). Its trunk, striking thanks to its silvery colour, and its leaves – green on top and whitish below – provide the ideal habitat for various species of wildlife.

White willow (Salix alba): White willows are abundant on the shores of L’Aubadera Island near the mainstem of the Ebro River thanks to their ability to withstand flooding. They are deciduous and have lanceolate leaves, like the rest of the trees in the willow family. Their dense branches offer protection and food for many birds and small mammals.

Narrow-leaved ash (Fraxinus angustifolia): This deciduous tree is present on the higher parts of the island, where the ground is drier. It is identifiable by its compound leaves, each made up of between seven and eleven long, narrow leaves. The narrow-leaved ash is one of the most widespread trees in the peninsula, especially in river-adjacent areas like L’Aubadera.

Common reed (Phragmites australis): This native species of reed is common on the riverbanks surrounding L’Aubadera Island and other floodplains. It is important to tell native reeds apart from exotic reeds, which have a stem with a diameter of up to 5 cm and can grow to up to 6 m tall.  Historically, reeds were used to build walls and roofs, using the wattle technique.

Invasive exotic species: Like many other ecosystems, L’Aubadera Island has its fair share of invasive exotic plant species. One notable case is the box elder (Acer negundo): an invasive tree species that can displace native vegetation and change the dynamics of riparian woodland, thus negatively impacting habitats and local species. Other significant exotic species present in the area include the giant cane (Arundo donax) and the rough cocklebur (Xanthium echinatum).

Finally, L’Aubadera’s natural heritage is a real asset for our health and can have direct benefits for us. For this reason, it must be respected through conservation efforts and observance of the permitted uses and activities.

Ebro Islands Wetland

Vernal pools: Essential for amphibians and biodiversity

In the past, thanks to the Ebro River’s frequent floods, small temporary pools and ponds formed and became a key source of biodiversity in the ecological pyramid. Many species of amphibians, reptiles, mammals and invertebrates depend on these vernal pools to survive.

Amphibians are currently among the most threatened groups of semi-aquatic species. Their numbers are decreasing in river habitats, and the Ebro River is no exception. Vernal pools offer the ideal habitat for all sorts of amphibian species, including frogs and toads. Amphibian larvae spend a significant proportion of their life cycle in these waters, where they feed and develop until metamorphosis.

These pools are also of vital importance to other wildlife, not just amphibians. Reptiles like the viperine water snake (Natrix maura), the grass snake (Natrix natrix) and the Spanish pond turtle (Mauremys leprosa) use these pools as a source of water and shelter. In addition, mammals like bats, the common genet (Genetta genetta), the common weasel (Mustela nivalis) and the beech marten (Martes foina) frequent the edges of vernal pools to find food.

These spaces, separate from the river’s mainstem, are also key for invertebrate biodiversity. Dragonflies, water beetles and other insects are common in this environment. As well as ensuring the ecosystem runs smoothly, the wealth of invertebrates in these areas provides food for many of the vertebrate species that live near the pools.

Vernal pools are biodiversity hotspots within the natural spaces of the Ebro Islands. They help to create an interconnected network of species that are part of the ecological pyramid in river environments. Protecting and preserving these pools is essential, both for local biodiversity conservation purposes and to maintain the health and resilience of the whole ecosystem.

 

Ebro Islands Wetland

The world of bats

In the shade of the leafy trees of the riparian woodland and in the most hidden spots of the Ebro Islands lives a fascinating population that is crucial for ecological balance in the local area: bats (Chiroptera). This protected area, recognised in the Catalogue of Wetlands of Catalonia, is known both for its beautiful scenery and for its biodiversity, which includes a wide variety of bat species.

The bats of the L’Aubadera nature area occupy all sorts of habitats, from caves to riparian forests. These flying mammals are experts at catching insects at night, thanks to their ultrasonic echolocation ability, which enables them to detect their prey in total darkness. According to estimates, a bat can eat around 500 insects in a night. This group of mammals plays a crucial role as pest control, eating insects that could be harmful to agriculture. When the sun sets, they take the baton from birds, which carry out this function during the day.

Most of the bats often seen flying around at dusk are the common pipistrelle, but other species that live in the area are also notable thanks to their unique characteristics and ecological importance:

Lesser horseshoe bat (Rhinolophus hipposideros)

This bat weight between 4 and 10 grams and has a wingspan of 192–252 millimetres. It is easy to spot thanks to its horsehoe-shaped noseleaf and brownish fur. It is a non-migratory species, but it does move short distances and lives in natural caves in colonies of up to 100 bats.

Nathusius’s pipistrelle (Pipistrellus nathusii)

This bat, with a wingspan of 230–250 mm and weight of 6–10 g, favours cracks in the bark of trees or bat boxes, though some colonies are still found in homes, farmhouses and churches. It is a migratory bat and can travel up to 2,000 km: one of the longest migrations in the world.

Daubenton’s bat (Myotis daubentonii)

Daubenton’s bat is similar in size to the others mentioned above and is often found in aquatic environments, though it is a highly adaptable species. It mainly lives in riparian woodland and can be identified easily because of its behaviour. When hunting, this bat flies just a few centimetres above the water’s surface. It feeds on various insects, including dipterans (flies), hemipterans, hymenopterans and lepidopterans, and even, sporadically, on small fish, which it catches straight from the water.

As well as controlling insect populations, these bats help to disperse seeds and contribute towards the preservation and balance of local biodiversity.

Bats are essential, fascinating inhabitants of the Ebro Islands nature area. Their presence both enriches the ecosystem and draws attention to the importance of protecting and preserving the natural habitats where they live.

 

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