Eastern Congolian Swamp Forests

This ecoregion, combined with the neighboring Western Congolian Swamp Forests, comprises one of the largest swamp forests in the world. Although the entire swamp forest is floristically similar, it was separated into an eastern and western section based on the significant ecological barrier that the Congo River presents to non-flying vertebrates, particularly primates. For example, the bonobo is absent on the right bank of the Congo River. 

The Swamp Forests are found on the left bank (facing downriver) of the Congo River and its tributaries, forming a large arc across the central portion of the Congo Basin. The ecoregion is almost entirely flat, and it is part of the wet tropics, with mean annual rainfall over 2,000 mm and mean maximum temperatures over 30ºC. Mean minimum temperatures range between 18 and 21ºC. Central Africa, mainly the DRC, has the highest concentrations of lightning observed on Earth, and this is expected to increase with climate change. 

The swamp forests provide regional sources of humidity that generate lightning-associated activity, thunderstorms, and convective rainfall. The soils are predominantly gleysols, indicating the considerable water-logging that the area experiences each year. 

The vegetation in this ecoregion consists of a mosaic of open water, swamp forest, seasonally flooded forest, dryland forest, and seasonally inundated savannas, all of which are affected by the seasonal flooding of the Congo River and its major tributaries. The seasonally flooded swamp forests are characterized by species such as Guibourtia demeusei, Mitragyna spp., Symphona globulifera, Entandrophragma palustre, Uapaca heudelotii, Sterculia subviolacea, and Alstonia congensis. The permanently flooded swamp contains monospecific stands of Raffia palm. Open areas are home to giant ground orchids and riverbanks are often lined with arrowroot.

These forests are defined as Guineo-Congolian swamp forests and riparian forest, part of the Guineo-Congolian regional center of endemism. The flora and fauna of this ecoregion is moderately species-rich, but contain few endemic species. The flora shares elements with both the Western Congolian Swamp Forests to the northwest and the Central Congolian Lowland Forests to the south. 

In the mammals, there is one strictly endemic rodent species, Muton’s soft-furred mouse. Avifaunal richness is moderately high, but there are no known endemics. Some Congo forest-restricted bird species present here include Congo sunbird, African river martin, and the Congo martin. Several amphibians and reptiles are near-endemic, but only one is strictly endemic: the tiny wax frog. 

The Congo River presents a formidable biogeographic and dispersion barrier to many species, with the clearest examples found among the primates. For example, Angolan colobus, Wolf’s guenon, bonobo, golden-bellied mangabey, and northern black mangabey occur only on the left bank of the Congo. In comparison, crowned guenon, chimpanzee, and grey-cheeked mangabey occur only on the right bank. 

Allen’s swamp monkey is found on both sides of the Congo River. This small, stout, and highly social primate with brown, gray, and green fur inhabits swamp forests but is often hunted for bushmeat or captured for the pet trade.

It is estimated that 124,000 km² of swamp forests remain in the Congo Basin, with perhaps half in this ecoregion. Parts of the Lomami National Park and Salonga National Park fall within this ecoregion, as well as huge areas of the Tumba-Lediima nature reserve (7,412 km²) and Tumba-Ngiri-Maindombe Ramsar Site, Wetland of International Importance (65,696 km²).

Human population densities are concentrated in villages along the major river systems and average around 12 persons per km². Logging and associated poaching are the major threats in this ecoregion due to the ease of access through the navigable waterways of the Congo River and its tributaries. Logging is occurring in the Tumba-Lediima nature reserve. 

Larger species are hunted for bushmeat, elephants are hunted for ivory and meat, and bonobos are hunted for meat, magical properties, and the pet trade. The poaching of African forest elephants in DRC is still rampant and is conducted by professional and well-organized poachers. Anecdotal information suggests that elephants have been hunted out from large areas. 

Priority conservation actions for the next decade

1. Incorporate local communities’ knowledge, livelihoods, participation, and land rights into conservation management. 
2. Facilitate a decreased demand and consumption of illegal products from the forests in wider society.
3. Encourage alternative livelihood opportunities that maintain tradition and culture.