The Ebro Delta (Delta de l'Ebre in Catalan) is the triangle of land that Spain's Ebro River has built into the Mediterranean in the province of Tarragona, Catalonia. It covers about 320 km² and pushes roughly 22 km out to sea, making it one of the largest wetlands of the western Mediterranean. It is a flat, wedge-shaped river delta of rice fields, coastal lagoons, salt pans, dunes and two sandy spits, the Punta del Fangar to the north and the Punta de la Banya to the south. About 7,800 hectares form the Ebro Delta Natural Park, created in 1983 and enlarged in 1986; 7,736 ha were added to the Ramsar list of wetlands of international importance in 1993, and in 2013 UNESCO made the delta part of the Terres de l'Ebre Biosphere Reserve. Around 95 bird species breed here and more than 300 have been recorded, which is why the delta is best understood through its animals and the places each one depends on.
Audouin's gulls and the Punta de la Banya
The delta's signature bird is Audouin's gull, a slim Mediterranean gull with a short red bill that feeds almost entirely on fish, often at night and well out to sea. In the late 1960s it was one of the rarest gulls in the world, with only about 1,000 pairs left. The Ebro Delta now holds the largest colony on Earth: in 2006 it reached a record of more than 15,000 pairs, and about 60% of the world's Audouin's gulls are reckoned to breed on the Banya. Adults here survive well, with an annual survival rate of about 90.5% measured in a 1999 study of the delta colony.
That colony lives on the Punta de la Banya, the southern spit, a flat peninsula of about 2,700 ha joined to the delta only by the narrow sand bar of the Trabucador. The whole Banya has been a partial nature reserve since 1986. Part of it is taken up by the Salines de la Trinitat, roughly 1,000 ha of salt pans and the only salt works still operating in the delta, thought to date back to the 14th century. The shallow evaporation ponds suit birds that most farmland cannot. Greater flamingos, slender-billed gulls, common, little and Sandwich terns, Kentish plovers, avocets, oystercatchers and shelducks all breed on the Banya, and about a hundred pairs of lesser black-backed gulls nest here in what is the species' only breeding colony in the Mediterranean.
The Banya also hosts the delta's reptile success story. Hermann's tortoises were released there in 1987 and 1988, and again between 1990 and 1993, from animals the park had been rearing in captivity. Monitoring since 1991 has shown them adapting well, and they now breed in the wild. In the bay and in the salt-pan ponds lives a large population of the fartet, or Spanish toothcarp, a fish rarely longer than 5 cm that is found only in Spain.
Glossy ibises and great egrets on the Illa de Buda
At the very tip of the delta, the river splits into two mouths around the Illa de Buda, an island of about 1,100 ha in the municipality of Sant Jaume d'Enveja. Only about 250 ha of it are rice fields; the rest is reed beds, rush meadows, glasswort flats and two connected lagoons called the Calaix Gran and the Calaix de Mar. The Calaix Gran takes fresh drainage water from the rice and grows pondweed, while the Calaix de Mar is flooded by the sea in easterly storms and grows salt-tolerant tasselweed.
In 1996 the European Commission chose a restoration project for Buda for LIFE-Nature funding. The work redirected nutrient-laden rice drainage away from the lagoons, opened channels to reduce oxygen loss, buried a power line that had been electrocuting birds, and turned more than 30 ha of paddies back into grazing marsh. Two species then nested on Buda that had never been known to breed anywhere in Catalonia: the glossy ibis and the great egret. Collared pratincoles and penduline tits followed. The glossy ibis has since boomed across the delta. In 2010 it was still listed as a recent and vulnerable breeder with 23 pairs, but by 2015 its numbers had passed 2,000 birds, helped by its taste for the invasive apple snail now common in the paddies.
Buda's plants are just as specific. A sea lavender described as new to science in 1998, Limonium vigoi, is known only from the Ebro Delta and one small stretch of coast at L'Ametlla de Mar.
Herons and the fartet in the Encanyissada and Tancada lagoons
The southern half of the delta is dominated by two large lagoons. The Encanyissada is the biggest in the delta, about 900 ha and only 114 cm deep at most, connected to the Bay of Els Alfacs through a natural channel called the Gola Vella. Together with the smaller Clot and Nòria lagoons and a grazed marsh known as Zona XII, the protected area totals about 932 ha. The tiny Nòria lagoon, cut off by a road and rice fields, is where most of the delta's heron species nest. On the Encanyissada itself, the fishermen's guild of Sant Pere still works the pantena, the oldest fixed fishing gear used in Catalonia.
The neighbouring Tancada, as its name ("the closed one") suggests, has no natural opening to the sea and exchanges water with the bay only through man-made ditches. Its southern edge meets the old Sant Antoni salt pans, so salt-loving plants grow beside its reed belt. North of the river lie the three-basin Canal Vell lagoon and Les Olles, the smallest lagoon in the delta, slightly brackish and of little importance for waterbirds. In all of them the underwater plants matter most, sheltering fish from heat and predators and serving as a major food source for waterbirds. Farm chemicals washing in from the fields have thinned that submerged vegetation in some lagoons, which is why water management here is as much about wildlife as about crops.
Rice fields: the 21,000-hectare wetland that sets the birds' calendar
Most of the delta is not wild at all. About three-quarters of its surface is farmland, and rice paddies cover roughly 21,000 ha. The Ebro Delta has held a Protected Designation of Origin for rice since 1992, covering varieties such as bomba and sènia grown in seven municipalities including Amposta, Deltebre and Sant Jaume d'Enveja. About 50,000 people live in the delta.
For wildlife, the paddies act as a seasonal wetland the size of a small city. From April to the September harvest, river water runs through canals into the fields, then into the lagoons and the sea. In December the gates close, the standing water slowly evaporates, and by the end of February the fields are almost dry. They are worked in March and flooded again in April. At its peak the cycle puts up to 40% of the delta underwater. It also produces an unusual inversion: the lagoons are saltier in winter than in summer, because summer brings a flood of fresh drainage water. Researchers have found that many birds, both ducks and songbirds, nest later here than at similar latitudes, timing their chicks to the months when the flooded paddies are most productive.
Fan mussels in the Fangar and Alfacs bays after Storm Gloria
The two spits enclose two shallow bays. Els Alfacs in the south, formed in the 16th century, is a platform of water only 1 to 2 m deep that receives about 275 million m³ of rice-field drainage a year, with meadows of the seagrasses Cymodocea nodosa and Zostera noltii on its floor. El Fangar lies in the north. Both became important for the noble pen shell, or fan mussel, a large bivalve found only in the Mediterranean.
From late 2016 a newly discovered parasite, Haplosporidium pinnae, killed about 99% of fan mussels along Spain's coast, and in December 2019 the IUCN listed the species as critically endangered. The Fangar had escaped the parasite, but in January 2020 Storm Gloria drove a surge up to 3 km inland across the delta's paddies and dumped sediment and rainwater into the bay. Of the 533 fan mussels counted in the Fangar before the storm, only 12 survived. That summer, surveyors found a dense population of 242 in the Alfacs, where few had been expected.
Blue crabs, dams and the sediment the delta no longer gets
New arrivals are changing the delta's food web. The Atlantic blue crab, after a failed attempt to settle in the Mar Menor in 2003, was found in the Ebro Delta in 2017 and has since spread so fast that it has upended the small-scale fishery. The zebra mussel is spreading through the delta and upstream. Meanwhile, the land itself is retreating. Dams on the lower Ebro at Mequinenza, Riba-roja and Flix trap sediment, and the river's sediment load fell by more than 99% over the last century; its mean flow dropped by about 29% in the 20th century. With less fresh water, a wedge of seawater pushes up the riverbed: about 5 km when the river runs at 300 to 400 m³/s, but as far as 32 km when it drops below 100 m³/s. Buda shows the cost. Its iron lighthouse, built in 1864 and 50 m tall, fell in a storm on 24 December 1961, and its stone replacement of 1962 was lost to the retreating shore by 1965.
For the river that feeds all this, read our Ebro River guide, and compare the delta's rice-and-flamingo landscape with the Camargue in France and Spain's other great bird wetland, Doñana in Andalusia.