The tropical rainforests in the Congo River basin are quite extensive and occupy the lowest-lying parts of the Congo Basin (depression). The Congo River basin is home to over 600 species of trees and more than 10,000 species of animals.
The Congo forests occupy the flat basin in the middle reaches of the Congo River and the small elevations surrounding it, with the region’s altitude ranging from sea level to Mount Stanley (5,110 m). The basin stretches on both sides of the equator, between the Atlantic Ocean and the East African Highlands. In the north, its border runs approximately along 5° N, and in the south, slightly south of 10° S.
The relief of the basin is clearly divided into several steps. Its lowest part forms a vast plain in the middle reaches of the Congo River with heights of no more than 500 m. It is mainly composed of a thick layer of ancient lake alluvium, and strips of young alluvial deposits stretch along the rivers. The surface of the plain is almost completely flat, as in the past it was the bottom of a lake that drained into the Atlantic Ocean. Its remnants are Lake Mai-Ndombe and Lake Tumba.
In the south and east, the flat surface of the central part of the basin transitions into a plateau 500–1,000 m high with a sharply defined escarpment. Its surface, composed of Paleozoic and Mesozoic sedimentary deposits, is cut by deep river gorges with numerous waterfalls. This structure of the valleys is the result of increased river erosion caused by uplifts that occurred at the end of the Mesozoic era, which led to the formation of this higher level of the basin.
The Congo Basin is a region of abundant rainfall and uniformly high temperatures. However, climatic conditions vary across its vast territory. The Congo Basin is located on the equator, with most of it on the southern side of the equator. The climate is tropical, hot, and humid in the low-lying equatorial regions, cooler and drier in the southern part of the highlands, and cooler and wetter in the eastern part of the highlands.
The forests of the Congo are the largest block of rainforests, with multi-tiered forests with a canopy height of over 30 m, and some tall trees reaching 50–60 m. Some tree species are deciduous, but evergreen and semi-evergreen species predominate. Epiphytes are very abundant, especially in the most humid ecotopes. The main large trees of the Congo Basin belong to the Meliaceae family: Entandophragma spp., Guarea cedrata, Guarea thompsonii, and Lovoa trichilioides. Other families include Maranthes glabra (family Chrysobalanaceae), Parkia bicolor (Fabaceae family), Pericopsis elata (Fabaceae family), and Petersianthus macrocarpus (Lecythidaceae family).
Flooded marshy areas in the Congo Valley and along the shores of lakes are covered with marsh grasses, among which papyrus predominates. In drier sandy areas of river valleys, you can find pure grasslands with tall grasses or thickets of low-growing trees.
The Congolese forests are a huge source of food and technical resources. These include oil palms and other palms, rubber trees, nutmeg trees, and various species of trees with valuable timber. The equatorial forests of Africa are characterized by the tsetse fly, which is widespread in the most humid areas, near rivers and lakes.
The rainforests of the Congo Basin are home to many endemic animals, such as the pygmy chimpanzee. Hippopotamuses inhabit the rivers, but their populations have been decimated by traditional hunting. Hunting hippopotamuses in Africa is prohibited, but it is still carried out illegally. Tropical forests are home to such well-known species as the western lowland gorilla Gorilla gorilla gorilla, the chimpanzee Pan troglodytes, and the okapi Okapia johnstoni. One of the most famous and priority species for conservation in the Congo Basin is the bonobo monkey Pan paniscus. Intensive hunting has led to a decline in the population of African forest elephants Loxodonta africanus cyclotis.
In the northeastern Congolese forests, there are 16 strictly endemic and almost endemic species of mammals, including the okapi Okapia johnstoni, the giant civet Genetta victoriae, and the water civet Osbornictus piscivora, as well as four species of shrews: Sylvisorex oriundus, Crocidura caliginea, Crocidura congobelgica, and Crocidura polii. There are 10 semi-endemic species, including the owl-faced monkey Cercopithecus hamlyni, the bearded monkey Cercopithecus lhoesti, the spotted bat Chalinolobus superbus and the white-spotted bat Chalinolobus alboguttatus, the soft-haired rat Praomys misonnei, and in the swamps, the Verschuren’s rat Malacomys verschureni. The region is also home to the endemic Congo peacock Afropavo congensis.
The West Congolese swamp forests were once home to a large population of forest (or African dwarf) buffalo Sycerus caffer nanus, but most of it has been exterminated. African buffalo, along with elephants and gorillas, prefer to stay in open areas within swamp forests. The Congo River itself is a major biogeographical boundary. Thus, many primates live only on the right bank of the Congo: for example, the crowned monkey Cercopithecus pogonias, the bearded monkey Cercopithecus cephus, the chimpanzee Pan troglodytes, the agile mangabey Cercocebus agilis, the gray-cheeked mangabey Lophocebus albigena albigenea, the Guereza colobus Colobus guereza, the potto Perodicticus potto edwardsi, and the golden angwantibo Arctcebus aureus. Another group of primates inhabits only the left bank: the Wolf’s monkey Cercopithecus Wolfi, the bonobo Pan paniscus, the golden-bellied mangabey Cercocebus galeritus chrysogaster, the black-crested mangabey Lophocebus aterrimus, and the dryas monkey Cercopithecus dryas. The subspecies of Demidoff’s galago Galagoides demidoff are distributed similarly: the subspecies Galagoides demidoff anomurus and Galagoides demidoff murinus are found only on the right bank of the Congo River, while Galagoides demidoff phasma is found only on the left bank. The Allen’s galago (Allenopithecus nigroviridis) inhabits both sides of the Congo River.
