The Republic of Congo has four ecoregions that occur partly within its borders as show in the figure below:
Western Congolian forest-savanna mosaic
Western Congolian forest-savanna mosaic
This ecoregion covers 159,700 square miles of critical/endangered tropical and subtropical grasslands, savannas, and shrublands in Angola, the Democratic Republic of the Congo, western Republic of Congo, and Gabon.
This ecoregion extends from the Sanaga River in west-central Cameroon south through Equatorial Guinea into the coastal and inland areas of Gabon, the Republic of Congo, and the Cabinda Province of Angola, ending in the extreme west Democratic Republic of Congo, just north of the mouth of the Congo River. At its southern extremity, the last 400 kilometers (km) of the ecoregion is a tongue of forest lying inland of the coastal plain and surrounded by the Western Congolian Forest-Savanna Mosaic.
The Atlantic Equatorial Coastal Forests ecoregion has exceptionally high levels of species richness and endemism, contains large blocks of evergreen lowland moist forest, and the central portion has one of the lowest human population densities in Africa. Most of the floral and faunal assemblages are intact, including assemblages of threatened large mammals, such as the western lowland gorilla (Gorilla gorilla gorilla), mandrill (Mandrillus sphinx), and sun-tailed monkey (Cercopithecus solatus). Important centers of endemism are found in this ecoregion, particularly in some of the coastal mountain ranges.
The Republic of Congo contains the Conkouati and Dimonika-Mayombe Reserves. However, given the vast forest areas remaining in the ecoregion and its exceptional importance, the number of protected areas is insufficient, their level of legal protection too low, and they are not representative of the entire range of existing habitats. Proposals have been made as to where additional protected areas should be located within areas of high biological priority.
The Northwestern Congolian Lowland Forests ecoregion stretches across four countries - Cameroon, Gabon, Republic of Congo, and the Central African Republic (CAR). It is bordered to the north and south by forest-savanna mosaics and to the east by swamp forest, while the western limit grades gradually into the lowland rain forests of the Atlantic Equatorial coastal forest ecoregion.
The Northwest Congolian Lowland Forest ecoregion contains vast tracts of lowland forest, supporting core populations of the western lowland gorilla (Gorilla gorilla gorilla) and large numbers of forest elephant. Species richness and endemism are both high. Logging concessions and associated bushmeat hunting and agricultural expansion are the main threats to the habitats and species. There are some established protected areas, and the gazettement of new protected areas offers good potential for biodiversity conservation in the region.
This ecoregion contains large areas of forest and forms a part of one of the world's last remaining tropical forest wildernesses. Around one third of the forest is classified as "frontier forests" that are largely in their natural state.
In Congo, Odzala–Koukoua National Park (over 13,000 km2) has recently been extended.
Most of the ecoregion has been allocated to forestry concessions. Even within protected areas, logging is a concern. Although logging in the region is selective and habitat conversion is limited, the major issue is the depletion of wildlife in logging concessions through hunting for bushmeat and poaching for ivory. There are also technical problems with the sustainability of logging operations and also of the political will both of regional governments and the logging industry to operate sustainably.
Logging roads and other infrastructure developments are contributing to the uneven loss of habitat throughout the ecoregion, with more accessible regions most affected. Although the impact of this fragmentation on biodiversity is still poorly understood, the population densities of sensitive species (e.g. chimpanzees) are known to decline.
Likouala à Epena, Republic of the Congo Photograph by Elie Hakizumwami Western Congolian Swamp Forests ecoregion stretches from eastern Republic of Congo through to the western portion of the Democratic Republic of Congo (DRC), and into the Central African Republic. This ecoregion lies on the western bank of the Congo River, which forms a major biogeographic barrier to the Eastern Congolian Swamp Forests and Central Congolian Lowland Forests.
The river in this section can be up to 15 kilometers (km) wide, and becomes braided in a maze of alluvial islands. The Western Congolian Swamp Forests have an irregular shape (reflecting riparian habitats) bounded by the right bank of the Congo River between the confluence of the Lualaba (Upper Congo) and the Lomami Rivers to the confluence of the Lefini and the Congo Rivers.
This ecoregion, combined with the neighboring Eastern Congolian Swamp Forests, contains one of the largest continuous areas of swamp forest in the world. Although relatively few species have been recorded, it remains largely intact and contains large populations of western lowland gorilla (Gorilla gorilla gorilla). Poaching is thought to have reduced populations of forest elephants (Loxodonta africana cyclotis) along the navigable waterways. Little research has focused on this region, and further efforts are necessary to better understand these forests and their species composition.
The ecoregion contains one large (4,390 km2) Ramsar site in the Republic of Congo, Lac Tl-Likouala-aux-Herbes Community Reserve, which was gazetted in 1998. The reserve is located along the River Likouala-aux-herbes, with four major tributaries Tanga, Mandoungouma, Bailly, and Batanga and the lake, Lac Tl, which is the home of the mythical giant dinosaur-like animal called Mokele Mbembe. The area is a good example of a freshwater tropical African wetland ecosystem with a diversity of habitats, including swamp forest, inundated savannas and floating prairies along the watercourses. The site is public property, owned by the local communities. A special zone of firm land and seasonally flooded forests, named Zone d'Utilisation Rationelle (ZUR, zone with sustainable use) is used for hunting.
Ecoregions are areas that:
 share a large majority of their species and ecological dynamics;
 share similar environmental conditions; and,
 interact ecologically in ways that are critical for their long-term persistence.
Scientists at the World Wildlife Fund (WWF), have established a classification system that divides the world in 867 terrestrial ecoregions, 426 freshwater ecoregions and 229 marine ecoregions that reflect the distribution of a broad range of fauna and flora across the entire planet.