Sangha Tri-National Park, Congo, Cameroon, DRC

Selective tree felling

Until the 1960s, the northern Congo was home to a vast, unfragmented tract of tropical rainforest where human activity was dominated by hunting-gathering and swidden agriculture.  Today, industrial logging is the most prominent land use in this area; over 90% of the forest area is in logging concessions.  Over 85% of the timber harvested are Entoandrophragma spp, commonly known as African mahogany (family Meliaceae).  The drastic modification of land use in a relatively short period of time has engendered rapid changes in this remote part of Central Africa. 

Forest people of Northern Congo

Since 2001, the INFORMS project has been working in collaboration with the Wildlife Conservation Society (WCS-Congo), the Congalaise Industrielle des Bois (CIB), and the Congolese Ministry of Forest Economy and Environment (MEFE) to map forest types and assess land-cover changes in the northern Congo. 

Natural Environment

The forests of the northern Congo are a mosaic of terra firma and swamp tropical rainforests.  The area has little topographic relief (elevation ranges from 300 to 600 m above sea level), and soils are generally nutrient-poor.  The northern Congolian rainforest is known for its tracts of remaining wilderness and high concentrations of large mammals, including the forest elephant, lowland gorilla, chimpanzee, and many other IUCN Red Listed species (see the WCS-Congo website for a complete list and brief descriptions of protected species found in this region). 

The predominant vegetation type in both northern Congo and the Sangha Tri-National Park is the mixed-species semi-evergreen terra firma forest.  This forest type can vary in its species composition, tree height, and crown size; it is marked by canopy gaps in a range of sizes and the presence of deciduous trees that lose their leaves during the dry season.  The second most prevalent vegetation type is the mono-dominant Gilbertiodendron devewrei evergreen forest.  Locally referred to as the “limbali forest”, this formation is composed predominantly of the tree species G. devewrei, a rarity in tropical rainforests.  The limbali forest occurs on both terra firma and seasonally flooded sites, and is characterized by a uniform and tightly connected canopy and an open understory that is almost entirely devoid of herbaceous undercover. 

Another forest type present in northern Congo is the Marantaceae formation of mixed-species semi-evergreen forest.  With trees dispersed in clumps and a wide-open canopy, this forest type resembles a woodland savanna when viewed from the air.  However, instead of grasses, the forest floor is covered with a dense carpet of herbaceous plants from the wild ginger (Zingiberacaea) and Marantaceae families.  This ground-covering vegetation often reaches a height of more than two meters, making it impossible to walk through without first clearing a path.  The thickness of the understory prevents sunlight from reaching the forest floor, resulting in a low recruitment rate of tree seedlings and relatively few small- and medium-sized trees in the Marantaceae forest. 

Other less common vegetation types in the Sangha Tri-National Park region include riparian forest and various types of wetland: “bai,” “yanga,” sedge-dominated (Cyperaceae) marsh, Raphia palm swamp, and mixed species swamp forest.  Some of these wetlands are the best places for sighting and observing forest animals.  For a more detailed description of the classification of vegetation in the region, please refer to The Vascular Plants of the Dzanga-Sangha Reserve by Dr. David H. Harris. 

Land Use

As in most of the Central African forests, humans have inhabited the region of northern Congo and the Sangha Tri-National Forest for thousands of years.  Traditional land use in the region consisted of subsistence activities, including hunting-gathering, shifting cultivation, fishing, and trapping.  During the period of European colonialism, exploitive activities such as slave trading, rubber tapping, ivory hunting, diamond mining, and logging became widespread.  However, the Sangha River region was among the last regions of Africa to be colonized by Europeans, and the scope of exploitation in this area was relatively limited.  Today, land use in northern Congo and the Sangha Tri-National Park region is dominated by wildlife conservation and large-scale industrial logging. 

In the early 1990s, international conservation efforts culminated in the establishment of a complex of international protected areas, including the Dzanga-Ndoki National Park and the Dzonga-Sangha Forest Reserve in the Central African Republic (1990), the Nouabalé-Ndoki National Park in the Republic of Congo (1993), and Lake Lobeké National Park in Cameroon (2001).  In 2003, The Congo Basin Forest Partnership incorporated these four parks into the Tri-National Park, one of eleven landscapes of conservation priority in Central Africa. 

Although parts of the Tri-National Park complex have been logged in the past, the Nouabalé-Ndoki National Park remains pristine and is only accessible by foot.  However, the park is now almost completely surrounded by active timber concessions.  Currently, there are over 70,000 km2 of timber concessions in the northern part of the Congo (slightly larger than the size of Ireland), making industrial logging the dominant land use in the region.  The majority of these concessions are in “primary” forest—areas currently without any road access that have never been logged before—and have been allocated only since the 1990s.  All of the concessions are run by foreign timber companies, often subsidiaries of large international corporations that operate in several neighboring countries in Central Africa.

Threats to Conservation

The rate of large-scale industrial logging in the northern Congo has accelerated significantly since its inception in 1930. Although the nature of timber harvest in the region is selective (high-grading versus complete forest clearing), its negative impacts on the forest are alarming.

The most direct effect of logging in the Sangha Tri-National Park is the depletion of commercial timber and the removal of aboveground biomass.    Over 85% of the timber harvested belong to the genus Entandrophrogma (African mahogany), and over 70% are of a single species, E. cylindricum (“sapelli” or “sapele”).  Although Entandrophragma  is a common genus in the forest of northern Congo, the future of its species is questionable if current harvesting trends continue without adequate forest management.  Moreover, the long-term effects on forest composition and structure could lead to further impoverishment of valuable timber species, devaluation of forest resources, and overall increased forest degradation.  This could in turn increase logging intensity from its current average of one tree per hectare, in effect creating a positive feedback cycle of intensifying forest decline.

As damaging as the direct impacts of timber harvests are, the indirect effects of industrialized logging are potentially even more devastating.  Employment opportunities with logging companies attract migrant workers from across Central Africa; as the population of the region grows, local pressures on the environmental also increase.  More forests are being cleared around settlements for agriculture, more forest animals are hunted and more fish caught to provide for the increasing demand for dietary protein.  The construction of logging roads and the consequent increase of human access into areas of previously inaccessible forest exacerbates the pressure on remaining forests.  The most damaging activities are the poaching of protected fauna (e.g. for ivory), commercial hunting of bush meat for export to major populations centers in Central Africa, and increased extraction of non-timber plant products.  Although some of these activities are part of the traditional land use, pressures on the forest have been amplified by the increasing presence of humans in the northern Congo.  Without proper management, the sustainability of both timber and non-timber forest products could be in jeopardy.

Dense Marantaceae forest in Sangha Tri-National Park

An IKONOS (remotely sensed) showing a bai with vegetation in red and inundated areas displayed in green

©Woods Hole Research Center, 2008