The Ciénaga Grande de Santa Marta is Colombia's largest coastal lagoon complex, a plain of lagoons linked by caños (channels), mangrove forests and marshes on the Caribbean coast of Magdalena department, between the outer delta of the Magdalena River to the west and the foothills of the Sierra Nevada de Santa Marta to the east. It covers about 4,280 km², of which roughly 730 km² is open water, and is fed by fresh water from the Magdalena's channels and the rivers of the Sierra, and by sea water entering mainly through a narrow mouth, La Barra, between Pueblo Viejo and the city of Ciénaga. It is protected by the Vía Parque Isla de Salamanca (created 1964) and the Ciénaga Grande de Santa Marta Flora and Fauna Sanctuary, was listed in 1998 as a Ramsar Wetland of International Importance covering about 400,000 hectares of the Magdalena estuarine delta, and was named a UNESCO biosphere reserve in 2000. Since the 1950s, though, roads, blocked channels, illegal dikes and farm runoff have killed large areas of its mangroves, and in 2017 a Ramsar advisory mission recommended adding it to the Montreux Record of threatened wetlands.
What follows sets out those threats in the order they arrived, and the protections that answered them.
How the 1950s coast road and blocked caños starved the lagoon
Highway 90 across Isla de Salamanca
The lagoon's natural seaward wall is Isla de Salamanca, not a single island but a chain of low islands, nowhere higher than about 6 m, built from sediment carried down by the Magdalena and separated by narrow channels. Naturally, this sandy barrier was permeable. Sea water moved in on the tides and winds, and in the rains the Ciénaga flushed salt back out, keeping a balance between fresh and salt water that the mangroves need.
In the 1950s the road from Barranquilla to Ciénaga, today Colombia's Route 90 (the Troncal del Caribe), was built along that barrier. Its embankments sealed many of the openings through which water had moved. With less exchange, and in a dry climate, the lagoon grew saltier. Rainfall on Isla de Salamanca averages only about 400 mm a year in the east and 760 mm in the west, while evaporation removes about 1,400 mm, so any loss of fresh water quickly shows up as rising salinity.
The Magdalena's caños and the Sierra rivers
The western side of the Ciénaga is fed by the Magdalena, Colombia's main river, which runs about 1,528 km before reaching the Caribbean at Bocas de Ceniza near Barranquilla. Its floods reach the lagoon through a web of caños (channels) and smaller lagoons, including the Pajarales complex, which holds about 564 million m³ beside the main lagoon's roughly 2,232 million m³. Caños such as Clarín Nuevo and Clarín Viejo also link the Ciénaga with the sea. As these channels were blocked, less river water reached the mangroves, compounding the effect of the road.
On the eastern side, fresh water comes from the Sierra Nevada through rivers such as the Frío, Tucurinca, Aracataca and Fundación, whose alluvial fans spread into the southeast of the estuarine plain. The same rivers cross the Zona Bananera, the banana-growing terrace that forms the lagoon's eastern edge and supplies the region's main exports, and roughly 1.2 million people depend on the Sierra's rivers for water; the Aracataca, for example, supplies the town of Aracataca. Every cubic metre drawn off upstream is a cubic metre that does not reach the estuary.
Mangrove die-off, dikes and the 2015 environmental convictions
The result was a large-scale mangrove die-off. Mangroves here, as along the rest of this coast, are mixed forests of red, black and white mangrove and buttonwood. Across the wider Magdalena–Santa Marta mangrove ecoregion, which runs from the Gulf of Urabá to La Guajira, almost half of the mangrove area was degraded over about 40 years by rising salinity and reduced fresh water caused by human development, and restoration work is under way on stands damaged by building and road construction between the 1950s and 1980s. On Isla de Salamanca itself, the road embankments and the blocked caños have left the mangrove dead in many places.
A newer threat came from the south of the lagoon. There, people built illegal dikes to dry out areas of marsh and take the land for private profit, causing sedimentation and speeding up the death of mangroves. On 30 August 2015 Colombia's Ministry of Environment announced the conviction of 12 people for environmental crimes in the Ciénaga Grande. The damage listed included illegal dikes, clearing of large areas for crops and cattle, cutting and burning of mangrove, deliberately set forest fires and illegal hunting of wildlife for sale.
People who live on the water carry much of the cost. In the stilt villages of Nueva Venecia and Buenavista, in Sitionuevo municipality, wooden houses stand on piles in the open lagoon, reached by boat. On the barrier in Puebloviejo municipality, the settlement of Tasajera has no piped drinking water or sewerage, and only about 30% of households have electricity; overexploitation and pollution mean that fishing alone no longer supports many residents. The striped mojarra, one of the most important catches, has been overfished, and a 2019 study found that about 5% of the mojarra sampled in the Ciénaga had swallowed plastic fibres or fragments.
One species shows how narrow the margin is. The sapphire-bellied hummingbird lives only in the mangroves of the Ciénaga Grande and the arid scrub right beside them, feeding mainly on the flowers of tea mangrove (Pelliciera rhizophorae). Its population is estimated at 285 to 440 mature birds and is believed to be falling. The IUCN listed it as Critically Endangered before downgrading it to Endangered in 2021. It occurs in two protected areas, but there are very few records from one of them, the Vía Parque.
Protection from 1964 to 2000: Salamanca, the sanctuary and the biosphere reserve
Formal protection began in 1964, when Isla de Salamanca was declared a national park to protect its bird life and coastal mangroves. Because the coast road already ran through it, it became the Vía Parque Isla de Salamanca, the only protected area in Colombia with the "road park" category. It lies within the municipalities of Ciénaga, Pueblo Viejo and Sitionuevo, bounded by the Caribbean to the north, the Ciénaga to the east, the Caño Clarín Nuevo and Ciénaga Pajaral to the south and the Magdalena to the west. Mangroves cover about a third of it, some 12,000 hectares, the most significant mangrove area on Colombia's Caribbean coast. Surveys list 199 bird species, more than 140 fish species, 35 reptiles, 33 mammals, nine amphibians and 98 invertebrates.
A second unit of Colombia's national park system, the Ciénaga Grande de Santa Marta Flora and Fauna Sanctuary, also protects part of the lagoon complex. In 1998 the Vía Parque's boundaries were redrawn and its category revised, the same year the delta was listed under the Ramsar Convention. Two years later, in 2000, UNESCO designated the area a biosphere reserve under its Man and the Biosphere programme, a status meant to combine strict core zones with sustainable use by the communities around them.
The protected status matters partly because of how much is at stake. Besides the birds, the wider Ciénaga supports spectacled caiman, American crocodile and iguana, red howler and capuchin monkeys, capybara and the manatee, in a mosaic of mangrove, flooded forest, dry tropical forest and aquatic vegetation. The mangroves are also nurseries for the fish that feed the lagoon villages: more than 130 fish species have been recorded in the mangroves around Santa Marta alone.
Ramsar in 1998 and the 2017 call for the Montreux Record
The Ramsar Convention came into force for Colombia on 18 October 1998, and the same year the country designated the "Sistema Delta Estuarino del Río Magdalena, Ciénaga Grande de Santa Marta" as a Wetland of International Importance, covering about 400,000 hectares (roughly 4,000 km²). The listing commits Colombia to maintaining the wetland's ecological character, though on its own it does not stop damage. The Montreux Record that would later be proposed for it dates from 1990, when the Ramsar parties set it up at their conference in Montreux, Switzerland; it held 48 sites in August 2021.
Nearly two decades later, a Ramsar advisory mission visited in 2017. It identified road construction, nitrates from fertilisers, toxic substances carried down the Magdalena, and logging, hunting and fishing for exotic species as the forces changing the wetland, and recommended that the site be placed on the Montreux Record, the Convention's list of Ramsar sites where ecological change has occurred, is occurring or is likely to occur and which need priority attention. Among the scientists who have campaigned for the lagoon is the marine biologist Sandra Vilardy, who wrote her 2009 doctoral thesis at the Autonomous University of Madrid on the Ciénaga as a social-ecological system and is widely recognised in Colombia for defending it.
The remedies the threats point to are hydrological as much as legal: reopening caños so that Magdalena water reaches the mangroves, restoring the exchange across Isla de Salamanca that the 1950s road reduced, keeping illegal dikes out of the southern marsh and cutting farm runoff from the rivers of the Sierra. How the Ciénaga fits among the world's other great mangrove systems is covered in our global guide to mangrove forests, its place among large wetlands in our list of the largest swamps and wetlands in the world, and the wider country in our Colombia country guide.