ECOSYSTEMS

Kahuzi-Biega National Park lies on the eastern edge of the Congo Basin, within the vast forests that form the second largest tropical rainforest system on Earth.

KBNP covers 6,000 km2 of primary tropical forest and boasts extraordinary biological diversity. It is one of the few parks in sub-Saharan Africa that protects a complete altitudinal range of wildlife and habitats, from lowland forests to Afro-montane forests, bamboo forests, and a few small areas of subalpine grasslands and heathlands on the Kahuzi and Biega mountains, which reach an altitude of approximately 3,300 m. Its great diversity of species (one of the highest in the Albertine Rift) and its endemism earned it a place on UNESCO's World Heritage List in 1980.

The Park is divided into two main ecological sectors. The highland sector lies to the east of the Park (where the Park headquarters are located in Tshivanga) and is covered by montane rainforest (or Afromontane forest). The much larger lowland sector is covered by Guineo-Congolian lowland rainforest It is one of the few regions in Africa where the transition between these two types of rainforests has remained largely intact. The two are linked by a narrow ecological corridor that is increasingly threatened by encroachment from herders and farmers.

KBNP is also located near some of the most densely populated areas in the DRC, with an estimated population of over 500,000 people around the Park headquarters in the highland sector and another 10,000 in the lowland sector. The Park is located near areas with very high human population density, such as Kasese, Itebero, Lulingu, Nkuku, Nzovu, and Mumbili. Some people living in these areas remained in the Park after its boundaries were defined in 1975.

The climate is equatorial, with temperatures hovering around 25°C during the day and 15°C at night throughout the year. Rainfall is very high, with an annual average of around 1,619 mm, but it is not evenly distributed throughout the year (Kahuzi-Biega Management Plan 2009-2019). There is a short dry season between January and February, a longer dry season from June to August, interspersed with two rainy seasons (short between March and May, and longer between September and December).

To date, more than 1,171 plant species have been recorded within the Park, of which 145 are endemic to the Albertine Rift (Plumptre et al., 2007), making it the fourth most botanically rich sites in the Albertine Rif (the top three are the Virunga National Park in DRC, Bwindi Impenetrable Forest in Uganda, and Mahale Mountains in Tanzania). Higher plants have been relatively well studied in the forests of Uganda and Rwanda, but elsewhere in the Albertine Rift, studies have been sparse. The list will grow considerably if we add the lower plants (mosses, liverworts, hornworts, algae, and lichens) and other poorly studied plant types such as climbing plants and epiphytes (Plumptre et al., 2007).

The mountainous part of the Park is covered with mainly forest vegetation, within which there are other formations linked to specific soil conditions: hydromorphic, marshy, flooded, or lateritic soils. The forests of KBNP are stratified by altitude. Between 700-1200m, the forests are lowland rainforest. Between 1200 and 1500m, there is a transition to submontane forest zone, and true montane forest grows above that altitude up to about 2000m. Above this, Afro-subalpine zones are dominated by swamp forests and peat bogs until about 2,600m, which is also the treeline. Finally, from here up to the summits are typical  montane scrub formations dominated by Ericaceae and dwarf shrubs (Steinhauer-Burkart et al., 1993, UNESCO, 1980).

The Park's protected vegetation cover has a regulating effect on the region's water regime. In particular, it protects the watersheds. In addition, KBNP's exceptional forest cover is an important carbon sink, contributing to the fight against global climate change.

The various types of habitats of the Park include:

Tropical montane forest and its secondary vegetation

It is located between  900 and 2,300 meters above sea level and is dominated by Albizia gummifera, Parinari excelsa, and Gambeya gorungosana. Up to an altitude of 1,350 meters, this forest is considered a "lowland forest." Above 1,800 meters, it becomes a "low mountain forest." Where humans have disturbed it in the past to create small areas of pasture for livestock, secondary forest is recolonizing; the best known is the Hagenia forest. Within the forests, there are patches of grassy savannah, due to past deforestation by humans; these savannahs are dominated by ferns (Pteridium capense).

High-altitude rainforest and its secondary vegetation

Located above 2,300 m in KBNP, dominated by Afrocarpus (Podocarpus) usambarensis (a conifer!), Syzygium guineense, and Psychotria mahonii, usually called "Podocarpus primary forest." The trees are shorter than at lower altitudes; tree ferns, hanging lichens, and other epiphytes abound. In areas previously cleared (by humans), there is a secondary forest of Myrianthus, and even areas dominated by Lobelias and patches of grassland.

Swamp forest

Although not extensive, patches of dense swamp forest can be found.

Bamboo forest and secondary vegetation

Almost dominated by a single species of bamboo - Oldeania (Arundinaria) alpina - and located between 2,300 and 2,600 m above sea level. The height is generally 15 meters, sometimes reaching 20 meters! Bamboo forests flower and seed collectively every 30-40 years, then die; they then grow back. They easily take over cleared land - the vast expanses we see today are the result of human logging in the past. Gorillas and chimpanzees enjoy the young bamboo shoots.

Subalpine heath

Above 2,600 m is a treeless zone dominated by Erica kingaensis (rugegensis). Here it is cold and temperatures can drop to 7°C. Visitors from temperate countries will recognize some types of plants, as they are typical of the Paleoarctic heathlands: Vacciniums (a type of blueberry or bilberry). The vegetation is dry, and plants such as Helichrysum can be seen. The ground is covered with thick moss.

Marshes and peat bogs

These habitats can be found at all altitudes up to 2,400 m. Similar areas exist throughout Central Africa (known as "bais" in Gabon and Congo) and are very attractive to gorillas, which come to feed on the green, fresh vegetation (mainly composed of sedges and easily digestible grasses). The peat here is formed by the symbiosis between a globally widespread species of rush and an endemic sphagnum moss.

Despite its global conservation importance, rich biodiversity, and resulting ecological benefits, deeply rooted threats related to human interactions with the Park are still present. In general, illegal occupation of the protected area, combined with the constant growth of the human population around the Park and the resulting demand for land for housing and agriculture, is the main threat to the Park. Deforestation is caused by illegal logging and charcoal production. Charcoal is used by households both in the areas bordering KBNP and in the city of Bukavu for cooking, as an alternative to the shortage of electricity to meet household needs. This deforestation is evident in both the highland and lowland sectors. Mining exploration and exploitation, as well as the presence of armed groups linked to mining, increase the demand for wild meat and treasure hunting in the Park.

These threats have made Kahuzi-Biega National Park a World Heritage Site in Danger since 1997. These threats do not allow for the persistence of biodiversity and the conservation of the Park's natural and cultural heritage and contribute to endangering its values.

In KBNP, land grabbing over several decades poses both direct and indirect threats to biodiversity. The establishment of settlements for farmers and farms within the Park, mainly in the ecological corridor, hinders progress towards conservation objectives and poses a serious threat to the Park's ecosystems.

These threats are interrelated and affect both conservation and the communities living around the protected area.