Magdalena River

• Category: Inland Aquatic Biomes.
• Geographic Location: South America.
• Summary: The Magdalena River is the main waterway and watershed in Colombia and runs through many of the country’s unique and important ecosystems.

The Magdalena River, known as the mother river of Colombia, is located in this northwestern South American country; it is the continent’s fifth-largest river basin. It runs through nearly 956 miles (1,540 kilometers), possessing a watershed of 99,397 square miles (257,438 square kilometers). The river covers almost a quarter of Colombia’s territory, crossing 11 of the 32 departments (provinces) that are home to nearly 70 percent of the nation’s human population.

The Magdalena River originates in the Central Andes range, within the Puracé National Natural Park, in a small lagoon of the same name located in the Páramo de las Papas (Potatoes Páramo). This name was coined by Rodrigo de Bastidas, a Spanish conqueror, who arrived at the river’s mouth in 1501; he named the waterway after the Christian iconic figure Mary Magdalene. The fluvial system of the river includes three main water courses: the Magdalena River (736 miles or 1,185 kilometers), the Cauca River (116 miles or 187 kilometers), and the Canal del Dique (70 miles, 114 kilometers).

Biodiversity

Generally, the watershed is divided into three sections—upper, middle, and low—each with important ecological, economic, and socially distinctive features. As the main entrance and arterial waterway for the country since pre-Hispanic times, the river has suffered from intensive and extensive use, from transportation to agriculture, fisheries, and irrigation. All of these have seriously impacted the river and the natural systems of the watershed.

Biologically, this system is one of the most complex and diverse biomes in the tropics because of its wide range of elevational floors. From páramos—the tundra-like scrubland ecosystem above the continuous forest line and below the permanent snowline—and Andean oak and cloud forests—also called fog forests, a tropical or subtropical evergreen montane moist forest type—in the upper parts of the river, to the coastal wetlands, mangroves, and lowland lagoons in the lower parts, this river represents the heart of Colombian ecological history. It is the perfect representation of the enormous diversity found in the country.

The three sections of the river are easily distinguishable from one another. Both the upper and lower Magdalena basins are typically dry and naturally dominated by forested landscapes until the sub-alpine elevations, where they become páramo. The upper part of the basin is generally more dry; its high-elevation regions are mostly dominated by high Andean ecosystems with some areas influenced by moist winds and cloud forests, while some other parts have mixed stands of mid- and high-elevation forests. This is the most populated portion of the country, and it includes the capital city of Bogotá. The natural ecosystems here have been seriously affected by both traditional and contemporary agricultural activities.

The dry peri-Caribbean zones of northern Colombia are located in the lower parts of the basin; these are some of the most interesting and complex wetland-lagoon-depression systems in South America. The river’s mouth to the Caribbean Sea—the Ciénaga Grande de Santa Marta wetland complex—is among the most unusual and important wetlands in Colombia. This complex includes the largest wetland in the country and unique mangroves. It is a wetland-lagoon fresh-salty water complex classified as a Biosphere Reserve, Important Bird Area, and a Ramsar Wetland of International Importance. The area is protected by several preserves, including the Via Parque, Isla de Salamanca, and Ciénaga Grande de Santa Marta Wildlife Sanctuary.

Between the dry upper and lower sections, the middle basin is mostly piedmont and isolated ranges from the Andes. Climatically, it is considered a wet/moist region. This section includes highly differentiated forest ecosystems, such as the unique geological complex of the Serranía de San Lucas. It also includes wetlands in the Depresión Momposina, or Mompox Depression.

Biota

Biologically, the Magdalena River area is a diverse and complex habitat system that features more than 190 freshwater fish species, 200 types of mammals, and nearly 400 bird varieties. For some groups, such as dry forest vegetation, more than 300 species are found only in few dry forest fragments across the basin. Mammals also are important for the basin, including most of the Andean and non-Amazon species, from small rice mice and the enormous spectacled bear to the Andean tapir in the upper parts of the region; to jaguar, puma, deer, and manatee in the lowlands. There is a fairly high incidence of species that are endemic (found nowhere else). For birds, the Magdalena represents a vital refuge that includes several Important and Endemic Bird Areas, from coastal and marine species to those that depend on high Andean native and migrant plants.

The vegetation along the river features such dominant trees as Spanish cedar (Cedrela odorata), the conifer (Podocarpus oleifolius), Spanish elm (Cordia alliodora), Andean oak (Quercus humboldtii), hemsl (Aniba perutilis), wild cashew (Anacardium excelsum), yellow lapacho (Tabebuia serratifolia), jacaranda (Jacaranda caucana), and palm trees such as Ceroxylon quindiuense, C. alpinum, C. parvifrons, and C. sasaimae. Several orchids are endemic here, including Cattleya trianaei to the upper Magdalena and C. warscewickzii to the San Lucas-Nechi region.

The upper Magdalena, in the Huila territory, has species of birds such as the burrowing owl (Athene cunicularia tolimae) and velvet-fronted euphonia (Euphonia concinna). Flora include the May flower or Christmas orchid (Cattleya trianaei), which is Colombia's national flower. In the hills along the cordilleras, there are other endemics such as Ceroxylon sasaimae, a flowering plant in the Arecaceae family; Odontoglossum crispum, an epiphytic orchid; honey tree; and others.

Large vertebrates in the forests surrounding the Magdalena include the mountain lion (Puma concolor), spotted cat (Leopardus tigrina), spectacled bear (Tremarctos ornatus), spider monkey (Ateles geoffroyi), Andean wolly monkey (Logothrix lagothricha lugens), Colombian tapir (Tapirus terrestris colombianus), mountain tapir (T. pinchaque), mountain paca (Agouti taczanowskii), red howler monkey (Alouatta seniculus), and several others. Among the birds, the blue-billed curassow (Crax alberti), huamán or mountain eagle (Oroaetus isidori), wattled guan (Aburria aburri), and yellow-eared parrot (Ognorhynchus icterotis) are on the verge of extinction. Also found here is the golden-headed quetzal (Pharomachrus auriceps), crested quetzal (P. antisianus), Andean cock-of-the-rock (Rupicola peruviana), and many more.

Migratory songbirds and raptors such as the rose-breasted grosbeak (Pheucticus ludovicianus), the broad winged hawk (Buteo platypterus), swainson’s hawk (B. swainsoni), and the summer tanager (Piranga rubra) use many areas of the Magdalena.

Species of special concern include the yellow-eared parrot (Ognorhynchus icterotis), the Christmas orchid, Andean rosewood (Aniba perutilis), Andean woolly monkey, the mountain tapir, spectacled bear, and wax palms (Ceroxylon spp.).

Environmental Impacts

As a result of pollution, overexploitation, transformation, and deforestation, the Magdalena River basin is one of the most seriously threatened biomes in South America. As the central artery of the country, the Magdalena is vulnerable to threats including overfishing; deforestation and the resulting erosion and sedimentation; agrochemical pollution; invasive species; interruption of natural flows due to water-management infrastructure; and the phenomena of El Niño and La Niña that, probably linked to related effects of global warming, have flooded the river’s shores. Although the Magdalena River area receives a lot of public attention, there are numerous communities and unique ecosystems that remain unprotected. However, there are a growing number of conservation efforts and zones, including 12 National Natural Protected Areas. Heritage Colombia, a new project announced in 2022, is expected to create and expand protected areas over a ten-year period.

Working with local Colombian authorities are several United States-based organizations. These include The Nature Conservancy, Great Rivers Partnership, and the U.S. Army Corps of Engineers. Colombian bodies involved in these cooperative efforts are led by the Ministry of Environment and the local environmental authority Cormagdalena. Their goals are to address the environmental needs of the basin, protect the Magdalena’s biodiversity, and secure the prosperity of its people who rely on the river for their livelihood. Particular attention is being paid to the dams, since they are both a boon to human water needs and a culprit in the declining fish populations here.

Bibliography

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