Bwindi Impenetrable Forest
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Bwindi Impenetrable National Park is a UNESCO World Heritage site occupying 331 km² that became a TEAM site in 2009. It is famous for its rare and endemic species the most ‘popular’ being mountain gorillas (Gorilla beringei beringei). Bwindi is a diverse natural forest area with a continuum of habitats ranging from 1190 meters to 2560 meters above sea level. The park lies within the Kigezi Highlands that were formed through up-warping of the western rift valley (“Albertine Rift” see below). The landscape is extremely rugged, with steep ridges and narrow valleys, and a general incline from the high deeply dissected south and southeast to the lower north and northwest. The only level areas within the park are the Mubwindi swamp (approximately 1km²) and Ngoto swamp (approximately 0.1km²).
Bwindi was managed as a productive forest reserve since 1932. In 1991, the forest gained National park status with the official name of ‘Bwindi Impenetrable National Park’. It is managed by the Uganda Wildlife Authority (UWA) as part of the Bwindi Mgahinga Conservation Area (BMCA). BMCA comprises Bwindi Impenetrable and Mgahinga Gorilla National Park (the Ugandan portion of the Virunga Mountains). BMCA is part of the Greater Virunga Landscape, which includes south western Uganda, eastern Democratic of Congo (DRC) and north western Rwanda.
Bwindi lies within a densely populated rural landscape with as many as 500 people/km² in some areas. The steep slopes immediately surrounding the park are heavily cultivated and thus forest cover stops abruptly at the park boundary. The majority of the families belong to Bantu people such as Bakiga and Bafumbira and a few to the Batwa “pygmy” people.
Local communities are allowed to collect specific forest products from designated areas of the park called ‘Multiple Use Zones’. These products include weaving materials, medicinal plants and honey. Tourism is a major source of income to park authorities and provides employment to local people.
Monitoring activities are administered through the Institute of Tropical Forest Conservation (ITFC), a field station of Mbarara University of Science and Technology, a Ugandan University, in collaboration with UWA. ITFC was established in 1986 as the Impenetrable Forest Conservation Project (IFCP) to work in conjunction with government’s Forest and Game Departments in order to control illegal activities in the forest, conduct inventory of Bwindi’s biological resources and develop capacity for the successful management and conservation of the forest. IFCP became ITFC in 1991.
ITFC is located at Ruhija (01°02’37” S and 18” E) on the edge of Bwindi at 2346 meters above sea level. The station’s facilities include office space, library, internet, meeting rooms, a students’ dormitory and 5 houses to accommodate staff and visitors.
The climate in Bwindi is equatorial with two rainfall peaks from March to May and September to November. Heavy mists often form in early mornings and after rainfall. The highest temperatures occur at the lowest altitudes and visa-versa and annual rainfall tends to vary between one and two meters.
Bwindi lies on the edge of the Albertine Rift, a valley which stretches from the northern tip of Lake Albert to the southern tip of Lake Tanganyika. This region is the most species rich region of comparable size in Africa for vertebrates and contains many endemic and threatened species. It is therefore a high priority area for conservation.
Bwindi is one of the few forests in East Africa where lowland and montane vegetation communities meet. It is believed to have served as a Pleistocene refugium, maintaining forest during the last ice age when most of the rest of the continent lacked forest cover and thus acted as a reservoir for forest dependent species that were lost elsewhere.
Bwindi is also a major catchment area, serving surrounding agricultural lands and the source of many rivers. These include the Ivi, Munyaga, Ishasha and Ntengyere, which drain into Lake Edward. The Ndego, Kanyamwabo and Shongi Rivers flow southwards towards Lake Mutanda.
A wide variety of vegetation forest types occur in Bwindi, broadly classified as medium altitude, moist evergreen and high altitude forest. The high altitude “Afromontane” forest is a highly restricted vegetation type on the African continent. The forest gets the name 'impenetrable' from the dense growth of herbs, vines and shrubs.
Bwindi’s forests have been given various names: Undifferentiated Moist Montane Forest (Langdale-Brown, 1960), Moist Montane Forest (Leggat and Osmaston, 1961), Tropical Low Montane Evergreen Rain Forest (Leggat and Osmaston, 1961), Parinari Forest (below 1500 m) and Prunus Africana Moist Montane Forest (above 1500m), Langdale-Brown et al. (1964), Mixed Forest with Chrysophyllum (Lind and Morisson, 1974) and Moist Lower Montane Forest (Hamilton, 1982).
Approximately 40% of the park is occupied by mixed forest that occurs at all altitudes and is characterised by a canopy with various species that often include the Red stinkwood (Prunus Africana), Newtonia (Newtonia buchananii), Symphonia globulifera, East African yellow wood (Podocarpus spp), and Strombosia scheffleri. The understorey commonly includes Xymalos monospora, Neoboutonia macrocalyx, Myrianthus holstii, Teclea nobilis and Allophylus abyssinicus.
Some formations are more limited by altitude. At around 1500 meters above sea level, Parinari excelsa dominated forest covers approximately 10% of the total area. A further 11% is dominated by Newtonia buchananii at around 2000 meters, and 8% by Chrysophyllum gorungosanum at around 2200 meters. Bamboo (Arundinaria alpina) dominated vegetation occupies only about 1% of the forest at the highest altitude (2400 meters to 2560meters above sea level) and the remaining 30% supports various vegetation communities including swamps, herbaceous cover and colonising forest.
The lowest altitude vegetation occurs in the northern block. This area includes stands of Parinari along the Ishasha and Ihihizo river valleys. In the valleys where deeper soils occur, the forests still include Entandrophragma (African mahogany) often associated with Newtonia buchananii, Aningeria adolfi-friederici and Symphonia globulifera. In poorly drained areas, stands of Syzygium guineense occur. Ocotea usambarensis reaches large sizes. On the higher ridges Podocarpus occurs. Disturbed forests of Albizia species, Milletia dura and Canthium vulgare occur especially close to perimeter of the forest. With time such forest is replaced by a late secondary formation typified by species such as Ficalhoa laurifolia, Hagenia abyssinica, Maesopsis eminii, Polyscias fulva and Nuxia congesta and often includes large lianas.
The main forest block to the south includes Chrysophyllum spp. associated with Entandrophragma, Newtonia and Prunus Africana but with smaller areas of dominant Parinari in some river valley bottoms. Podocarpus milanjianus, once common, has been greatly depleted by historical exploitation. Podocarpus gracilior remains common along swamp edges. The vegetation gets shorter at higher altitudes and often includes open herbaceous areas. These support thick growth of herbaceous plants including Mimulopsis solmsii, Mimulopsis arborescens and bracken fern (Pteridium aquillinum) and are a major feeding location for mountain gorillas, elephants and other ground dwelling animals. It is not clear how much of the open vegetation is natural and how much can be attributed to past anthropogenic disturbance including logging and fire during the early and mid 20th century. Elephant activity also contributes to the creation and maintenance of the open areas.
The swamps too are important for animals, hosting a number of restricted species of birds and amphibians. They appear to attract elephants (Loxodonta africana) during the dry season.
Bwindi is one of the most prominent forests in Africa in terms of mammal diversity, supporting at least 120 known species. It contains about half of the world's mountain gorillas (Gorilla beringei beringei). Another globally threatened primate is the endangered Eastern Chimpanzee (Pan troglodytes schweinfurthi). Bwindi also hosts Blue Monkey (Cercopithecus mitis), Red-tailed Monkey (Cercopithecus ascanius), Black and White Colobus Monkeys (Colobus guereza), Baboon (Papio anubis) and l’Hoest’s Monkeys (Cercopithecus l’hoesti) along with three nocturnal primate species namely the Potto (Perodicticus potto), Demidoff’s Galago (Galagoides demidoff) and the Spectacled Galago (Galago matschiei). The park supports Elephants (Loxodonta africana), Bush Pigs (Potamochoerus larvatus), Giant Forest Hog (Hylochoerus meinertzhageni), Black Fronted Duiker (Cephalophus nigrifrons), Yellow Backed Duiker (Cephalophus silvicultor), Clawless Otter (Aonyx capensis), Side Stripped Jackal (Canis adustus), Civet (Civettictis civetta) and numerous other species, especially of bats and rodents.
Bwindi also supports at least 348 bird species of which 75 are restricted-range species. Eight species are not known to occur anywhere else in East Africa including; Fraser’s Eagle Owl (Bubo poensis), Dwarf Honeyguide (Indicator pumilio), African Green Broadbill (Pseudocalyptomena graueri), White-bellied Robin Chat (Cossyphicula roberti), Grauer’s Rush Warbler (Bradypterus graueri), Short-tailed Warbler (Hemistesia neumanii), Chaplin’s Flycatcher (Muscicapa lendu), Yellow-eyed Black Flycatcher (Melaenornis ardesiacus), DuskyTwinspot (Euschistospiza cinereovinacea).
Fifty three species are forest dependent species and are confined predominantly to highland forest. Twenty three species are endemic to the Albertine Rift area. Four globally threatened species, all categorised as vulnerable are known to occur, namely African Green Broadbill (Pseudocalyptomena graueri), Grauer’s Rush Warbler (Bradypterus graueri), Chaplin’s Flycatcher (Muscicapa lendu), and Shelley’s Crimson- wing (Cryptospiza shelleyi).
Twenty seven amphibian species have been identified. Eleven are endemic to the Albertine Rift. Six are of global conservation concern including the Western Rift Leaf-folding Frog (Afrixalus orophilus) (IUCN category “vulnerable” VU) and Ahl's Reed Frog (Hyperolius castaneus) (IUCN category “vulnerable” VU). Fourteen snake species, 9 of which are endemic to Bwindi are known. Six species of chameleon, 14 species of lizards have also been recorded.
Bwindi hosts at least 220 butterfly species including 8 Albertine rift endemics. Three butterflies occur only in Bwindi: the Cream- banded swallowtail (Papilio leucotaenia), Graphium gudenusi and Charaxes fournierae. The threatened African giant swallowtail (Papilio antimachus) is also found in Bwindi. Very little is known about Bwindi’s other invertebrates though there has been limited work on molluscs and aquatic arthropods.
Floristically Bwindi is amongst the most diverse forests in East Africa. More than 1,000 flowering plant species, 324 tree and shrub species and more than 104 species of ferns have been identified.
The northern (low altitude) sector is rich in species of the Guineo-Congolian flora. These include two species internationally recognised as endangered, Brown mahogany (Lovoa swynnertonii) and Brazzeia longipedicellata (Hilton-Taylor, 2002).
Ten tree species occur nowhere else in Uganda: Allanblackia kimbiliensis, Brazzeia longipedicellata, Chrysophyllum pruniforme, Croton bukobensis, Grewia mildbraedii, Leplaea mayombensis, Maesobotrya purseglovei, Melchiora schliebenii, Strombosiopsis tetrandra and Xylopia staudtii. Species such as Allanblackia kimbiliensis, Brazzeia longipedicellata, Dicranolepis incisa, Milletia psilopetala and Sampium leonardii-crispi need special attention because they are found in only one other country in addition to Uganda. Allanblackia kimbiliensis, Dicranolepis incisa and Sampium leonardii-crispi have been recorded in Congo in addition to Uganda while Brazzeia longipedicellata, Milletia psilopetala have been recorded in Congo.
Common canopy species include: Chrysophyllum gorungosanum, Entandrophragma excelsum, Newtonia buchananii, Parinari excelsa, Podocarpus milanjianus, Prunus Africana and Symphonia globulifera. Less common distinctive species include: Allanblackia floribunda, Balthasaria schliebenii, Ekebergia capensis, Ocotea usambarensis and Zanthoxylum gilletii.
Typical sub-canopy trees include: Albizia gummifera Allophylus abyssinicus, Beilschmiedia ugandensis, Carapa grandiflora Cassipourea ruwensorensis, Croton macrostachys, Dichaetanthera corymhosa , Dombeya goetzenii, Drypetes gerrardii, Faurea saligna , Ficalhoa laurifolia, Leplaea mayombensis, Harungana madagascariensis, Ilex mitis, Macaranga kilimandscharica, Neoboutonia macrocalyx, Olea capensis, Olinia usambarensis, Polyscias fulva, Strombosia scheffleri, Syzygium guineense and Tetrorchidium didymostemon.
Common understorey species include: Allophylus macrobotrys, Cyathea deckenii, Psychotria mahonii, Lobelia giberroa, Myrianthus holstii, Rytigynia sp, Tabernaemontana holstii, Teclea nobilis and Xymalos monospora.
Bwindi is located in south-western Uganda on the edge of the western rift valley and touches the border of the Democratic Republic of Congo. The park is located in Rubanda County of Kabale district, Kinkizi county of Kanungu district and Mutanda county of Kisoro district. Bwindi is about 29 km by road to the north- west of Kabale town and 30 km north of Kisoro town. The drive from Kabale to ITFC takes 2 hours.
Institute for Tropical Forest Conservation: http://www.itfc.org
Albertine Rift Programme http://www.albertinerift.org
Wildlife Conservation Society, Uganda http://www.wcs.org/where-we-work/africa/uganda.aspx