Lake Barombi Mbo Forest Reserve

Elefanten See (Elephant Lake)

CMNTIPA032
Lake Barombi Mbo Forest Reserve

Country: Cameroon

Administrative region: Southwest (Region)

Central co-ordinates: 4.66130 N, 9.40200 E

Area: 9.26km²

Qualifying IPA Criteria

A(i)Site contains one or more globally threatened species

IPA assessment rationale

Although a small site, with c.40% of the area open water, Barombi Mbo Forest Reserve qualifies as a potential IPA under criterion A(i) through several globally threatened species, including two considered Critically Endangered and globally endemic to this site, Acridocarpus staudtii and Rhaphiostylis poggei.

Site description

Lake Barombi Mbo is a deep crater lake with a narrow surrounding perimeter of tropical forest, located above the town of Kumba in Meme Division, Southwest Region, Cameroon. It is an internationally recognised RAMSAR site (no. 1643), within a slightly larger national Forest Reserve. The Forest Reserve, covering 926 ha, was established in 1940 by order No. 17, subsequently falling under the 1994 Forest Law (Law No. 94-01) (Fonge, 2019; Schliewen, 2006). The RAMSAR designation, bestowed in 2006 to make it Cameroon's second RAMSAR site, covered only the lake itself and crater rim (415 ha). It was based largely on the remarkable diversity of endemic, sympatrically evolved cichlid fish species and the consequent global significance of the site to evolutionary biology (Schliewen, 2006).

Botanical significance

Together with the larger Southern Bakundu Forest Reserve, Barombi Mbo was considered a second-tier, "meso" hotspot for threatened species by Onana & Cheek (2011). The site is historically important as the original collecting location of several species collected by Preuss and Staudt in the nineteenth century. Much of the more recent scientific collecting at the site and nearby has been by Duncan Thomas of Missouri Botanic Gardens, who lived at Kumba in the 1980s (Onana & Cheek, 2011).
The site is considered the sole location in the world for Acridocarpus staudtii (CR) which was rediscovered there in 1986 and 1999 nearly a century after it was initially collected by Staudt. It is also the site of the only Cameroonian collections of Thunbergia rufescens (CR) and Rhaphiostylis poggei (CR), also made in the 1890s (Lovell & Cheek, 2020a,b). Unfortunately these species have not been rediscovered here and, while the former has been collected in Nigeria, the latter has never been found elsewhere and is thought possibly extinct. Preuss also first collected Dielsantha galeopsoides (NT) from the location, where again it has also not been recollected. It remains rare but not threatened, having been collected at several other sites (Cheek and Thulin, 2015). Other threatened species such as Pancovia polyantha (CR), Crotonogyne impedita (CR), Deinbollia macrantha (CR) and Strombosia gossweilleri (EN) have been found nearby but not necessarily at the lake site itself (Cheek & Lovell, 2020; Onana & Cheek, 2011).
Pollen cores indicating continuously low grass pollen percentages through the last 25,000 years suggest the Barombi Mbo area may have been a refuge for forest taxa (Giresse 1991; Maley et al., 1990).

Habitat and geology

The crater lake was formed by an explosive eruption around 1 Ma which punched through basaltic layers and older basement complex rocks (Maley et al., 1990). Three successive volcanic series are evident at the site, a Tertiary age "lower black series", a Neogene "medium white series" of trachytes and phonolites, and a Quaternary basaltic "upper black series". The latter series is most prominent but older basement-complex crystalline rocks also outcrop in the catchment area west of the lake and influence the lake sediment (Maley, 1990; Giresse et al., 1991). Within the steep, c.100 m crater wall itself, two similar series of basaltic tuff lapilli are evident (Schliewen, 2006).
The surface of the lake today is approximately 315 m.a.s.l. Unlike some similar crater lakes in the region, Lake Barombi Mbo has an inflow and outflow. The outlet, the Kaké, believed to be of recent age, flows through a steep gorge in the southeastern rim and serves the town of Kumba as the major water resource before joining the Mungo river system (Schliewen, 2006). The inlet on the eastern side, the river Sofo, and its tributary Toh Mbok, are disconnected from major river systems and the drainage basin extends only to the perimeter of the older, secondary crater area (c. 8 km2) immediately adjacent to the lake.
The site has a two-season equatorial climate with a short dry season from December to February and 3,000–4,000 mm total precipitation per year (Fonge et al., 2019). Schliewen (2006) reports a lower range of 1,825–3,000 mm p.a. Mean annual temperature is reported as 18° C by Schliewen (2006), with humidity ranging between 70–84%.
The lake lies within Letouzey & Fotius's (1985) wet Atlantic–Biafran zone of the evergreen, Guineo–Congolian rainforest (Cross–Sanaga–Bioko coastal forests ecoregion of Olson et al., 2001). More precisely, it is part of subcategory 228, "Foret Atlantiques biafreenes à Caesalpinaceae", of Letouzey & Fotius's (1985) vegetation classification. However, pockets of semi-deciduous forest also occur in this area.

Conservation issues

The nearby town of Kumba is a regional transport hub and trade centre with a growing population. Demand for land, timber and fuel wood associated with this growth have driven extensive habitat loss and degradation in the area, and these are the main threats to the forest at Barombi Mbo (Cheek & Lovell, 2020; Fonge et al., 2019; Sounders and Kimengsi, 2011). Fonge et al. (2019) found that 90% of dense forest cover in the 3,000 ha surrounding the lake had been lost between 1986 and 2014, mainly through conversion to open forest and forest mosaic. Cocoa cultivation appears to be a major driver of this change, along with oil palm and subsistence crops like cocoa yams (Fonge et al., 2019). An agro-industrial plantation has also been designated 1 km to the north of the lake (MINFOF & WRI, 2020) and satellite imagery suggests it may already have exceeded its boundaries in the direction of the lake.
A greater proportion of dense forest has survived in the area immediately bordering the lake which constitutes the protected area (Fonge et al., 2019). However, this is unlikely to be large enough to support rare species in isolation in the long-term, and this forested perimeter has also suffered loss, with farming occurring within the crater rim itself (Schliewen, 2006; Fonge et al., 2019).
Conversion to farmland threatens the aquatic biodiversity of the lake. The western rim of the lake is lower than that on the other sides and there is consequently a large catchment area to the immediate west of the lake, apparently on the site of a second, shallow, filled-in lake crater (Giresse et al., 1994). Ferralitic soils have developed on this area and there are many scattered buildings and signs of forest clearance and agriculture. Apart from loss of forest, disturbance to this area threatens the high clarity and unique chemical balance of the lake water (Schliewen, 2006). It is to be recommended that this area is treated as part of the conservation area up to the watershed approximately 2 km west of the lake's west rim. This would also increase the area and chance of survival for threatened plant species. Regular fish-death events seem to take place associated with increased turbidity from natural causes but pesticide contamination, and phosphate and heavy metal enrichment from cocoa farms could also threaten the lake ecology (Fonge et al, 2019; Schliewen, 2006).
Over-fishing and apparent introduction of non-native fish species are additional threats to the extremely important aquatic fauna (Schliewen, 2006). Unsustainable extraction of drinking water for the growing town of Kumba may also become a concern (Schliewen, 2006)
Kumba has good transport connections and the site is a potential tourist attraction. This has so far not been developed, but local schools use the site for educational purposes (Schliewen, 2006).

Ecosystem services

The lake contains a remarkable 12 endemic species of sympatrically evolved fish, making it one of the densest and most biologically remarkable sites for endemic fish species in the world (Schliewen et al., 1994; Schliewen, 2006). Freshwater sponges are also present, including the endemic Corvospongilla thysi (Schleiwen, 2006).
The lake is the main source of clean water for Kumba (Schliewen, 2006). The surrounding forest is likely to be essential to maintaining good water quality through prevention of soil erosion, sedimentation and eutrophication (Schliewen, 2006).
To the Barombi people the lake is a sacred site (Schliewen, 2006). It is also relied upon for food and income through fishing (Schliewen, 2006).
The lake is 110 m deep and 4.5 km in area making it the largest crater lake in Cameroon. It is one of the oldest dated lakes in Africa at approximately 1 Ma, and a valuable source of information about past climate and habitat (Giresse et al., 1994).

Site assessor(s)

Bruce Murphy, Royal Botanic Gardens, Kew

Martin Cheek, Royal Botanic Gardens Kew

IPA criterion A species

Species Qualifying sub-criterion ≥ 1% of global population ≥ 5% of national population 1 of 5 best sites nationally Entire global population Socio-economically important Abundance at site
Psychotria minimicalyx K.Schum A(i) True True True False False
Pavetta muiriana S.D.Manning A(i) True True True False False
Rutidea nigerica Bridson A(i) False False True False False
Whitfieldia preussii (Lindau) C.B.Clarke A(i) True False False False False
Calycobolus micranthus (Dammer) Heine A(i) True True True False False
Medusandra richardsiana Brenan A(i) True True True False False
Pauridiantha divaricata (K.Schum.) Bremek. A(i) True True False False False
Aristolochia preussii Engl. A(i) True False True False False
Trichostachys interrupta K.Schum. A(i) True False True False False
Isonema buchholzii Engl. A(i) True True True False False
Acridocarpus staudtii (Engl.) Engl. ex Hutch. & Dalziel A(i) True True True True False
Thunbergia rufescens Lindau A(i) True True True False False
Ritchiea macrantha Pax & Gilg A(i) False True True False False
Rhaphiostylis poggei Engl. A(i) True True True True False
Deinbollia macrantha Radlk. A(i) True True True True False
Begonia preussii Warb. A(i) True False False False False
Psychotria moliwensis fernandopoensis A(i) True False True False False
Strychnos staudtii Gilg A(i) True False False False False
Trichilia zewaldae J.J.de Wilde A(i), A(iii) True False True False False
Pancovia polyantha Gilg ex Engl. A(i) True True True True False
Psychotria asterogramma O.Lachenaud A(i) False False True False False

Psychotria minimicalyx K.Schum

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Pavetta muiriana S.D.Manning

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Rutidea nigerica Bridson

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
False
≥ 5% of national population:
False
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Whitfieldia preussii (Lindau) C.B.Clarke

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
False
1 of 5 best sites nationally:
False
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Calycobolus micranthus (Dammer) Heine

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Medusandra richardsiana Brenan

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Pauridiantha divaricata (K.Schum.) Bremek.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
False
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Aristolochia preussii Engl.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
False
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Trichostachys interrupta K.Schum.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
False
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Isonema buchholzii Engl.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Acridocarpus staudtii (Engl.) Engl. ex Hutch. & Dalziel

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
True
Socio-economically important:
False
Abundance at site:

Thunbergia rufescens Lindau

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Ritchiea macrantha Pax & Gilg

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
False
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Rhaphiostylis poggei Engl.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
True
Socio-economically important:
False
Abundance at site:

Deinbollia macrantha Radlk.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
True
Socio-economically important:
False
Abundance at site:

Begonia preussii Warb.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
False
1 of 5 best sites nationally:
False
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Psychotria moliwensis fernandopoensis

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
False
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Strychnos staudtii Gilg

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
False
1 of 5 best sites nationally:
False
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Trichilia zewaldae J.J.de Wilde

Qualifying sub-criterion:
A(i), A(iii)
≥ 1% of global population:
True
≥ 5% of national population:
False
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

Pancovia polyantha Gilg ex Engl.

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
True
≥ 5% of national population:
True
1 of 5 best sites nationally:
True
Entire global population:
True
Socio-economically important:
False
Abundance at site:

Psychotria asterogramma O.Lachenaud

Qualifying sub-criterion:
A(i)
≥ 1% of global population:
False
≥ 5% of national population:
False
1 of 5 best sites nationally:
True
Entire global population:
False
Socio-economically important:
False
Abundance at site:

General site habitats

General site habitat Percent coverage Importance
Forest - Subtropical/Tropical Moist Lowland Forest No value Major

Forest - Subtropical/Tropical Moist Lowland Forest

Percent coverage:
No value
Importance:
Major

Land use types

Land use type Percent coverage Importance
Nature conservation 45 Major
Agriculture (arable) No value
Tourism / Recreation No value
Forestry 100

Nature conservation

Percent coverage:
45
Importance:
Major

Agriculture (arable)

Percent coverage:
No value
Importance:

Tourism / Recreation

Percent coverage:
No value
Importance:

Forestry

Percent coverage:
100
Importance:

Threats

Threat Severity Timing
Agriculture & aquaculture - Annual & perennial non-timber crops - Shifting agriculture High Ongoing - increasing
Pollution - Agricultural & forestry effluents - Nutrient loads Unknown Future - inferred threat
Pollution - Agricultural & forestry effluents - Soil erosion, sedimentation Unknown Future - inferred threat
Pollution - Agricultural & forestry effluents - Herbicides and pesticides Unknown Future - inferred threat
Invasive & other problematic species, genes & diseases - Invasive non-native/alien species/diseases High Future - inferred threat
Natural system modifications - Dams & water management/use - Abstraction of surface water (domestic use) Medium Future - inferred threat
Residential & commercial development - Housing & urban areas Medium Ongoing - trend unknown
Agriculture & aquaculture - Annual & perennial non-timber crops - Agro-industry farming Medium Ongoing - trend unknown
Biological resource use - Logging & wood harvesting High Ongoing - trend unknown
Biological resource use - Fishing & harvesting aquatic resources Medium Ongoing - trend unknown

Agriculture & aquaculture - Annual & perennial non-timber crops - Shifting agriculture

Severity:
High
Timing:
Ongoing - increasing

Pollution - Agricultural & forestry effluents - Nutrient loads

Severity:
Unknown
Timing:
Future - inferred threat

Pollution - Agricultural & forestry effluents - Soil erosion, sedimentation

Severity:
Unknown
Timing:
Future - inferred threat

Pollution - Agricultural & forestry effluents - Herbicides and pesticides

Severity:
Unknown
Timing:
Future - inferred threat

Invasive & other problematic species, genes & diseases - Invasive non-native/alien species/diseases

Severity:
High
Timing:
Future - inferred threat

Natural system modifications - Dams & water management/use - Abstraction of surface water (domestic use)

Severity:
Medium
Timing:
Future - inferred threat

Residential & commercial development - Housing & urban areas

Severity:
Medium
Timing:
Ongoing - trend unknown

Agriculture & aquaculture - Annual & perennial non-timber crops - Agro-industry farming

Severity:
Medium
Timing:
Ongoing - trend unknown

Biological resource use - Logging & wood harvesting

Severity:
High
Timing:
Ongoing - trend unknown

Biological resource use - Fishing & harvesting aquatic resources

Severity:
Medium
Timing:
Ongoing - trend unknown

Protected areas

Protected area name Protected area type Relationship with IPA Areal overlap
Barombi Mbo Forest Reserve Forest Reserve (conservation) protected/conservation area matches IPA 9

Barombi Mbo Forest Reserve

Protected area type:
Forest Reserve (conservation)
Relationship with IPA:
protected/conservation area matches IPA
Areal overlap:
9

Conservation designation

Designation name Protected area Relationship with IPA Areal overlap
Barombi Mbo Crater Lake Ramsar IPA encompasses protected/conservation area 4

Barombi Mbo Crater Lake

Protected area:
Ramsar
Relationship with IPA:
IPA encompasses protected/conservation area
Areal overlap:
4

Management type

Management type Description Year started Year finished
No management plan in place No value No value

No management plan in place

Year started:
No value
Year finished:
No value

Bibliography

Onana J.-M. & Cheek M., 2011

Red Data Book of the flowering plants of Cameroon

Letouzey, R., 1985

Notice de la carte phytogéographique du Cameroun au 1: 500,000.

Olson, D.M. et al., 2001

Terrestrial ecoregions of the world: a new map of life on earth

Bioscience, Vol 51, page(s) 3-938

Fonge, B.A., Tabot, P.T., Bakia, M-A. & Awah, C.C., 2019

Patterns of land-use change and current vegetation status in peri-urban forest reserves: the case of the Barombi Mbo Forest Reserve, Cameroon

Geology, Ecology, and Landscapes, Vol 3(2), page(s) 104-113

Giresse, P., Maley, J., & Brenac, P., 1994

Late quaternary palaeoenvironments in the Lake Barombi Mbo (West Cameroon) deduced from pollen and carbon isotopes of organic matter

Palaeogeography, Palaeoclimatology, Palaeoecology, Vol 107, page(s) 65–78

Schliewen, U., Tautz, D. & Pääbo, S., 1994

Sympatric speciation suggested by monophyly of crater lake cichlids

Nature, Vol 368, page(s) 629-632

Schliewen, U., 2006

Barombi Mbo Crater Lake: RAMSAR information sheet

Available online

Maley, J., Livingstone, D.A., Girsse, P., Thouveny, N., Brenac, P., Kelts, K., Kling, G., Stager, C., Haag, M., Fournier, M., Bandet, Y., Williamson, D. and Zogning, A., 1990

Lithostratigraphy, volcanism, paleomagnetism and palynology of Quaternary deposits from Barombi Mbo (West-Cameroon): preliminary results

Journal of Volcanology and Geothermal Research, Vol 42, page(s) 319-335

Giresse, P., Maley, J., & Kelts, K., 1991

Sedimentation and palaeoenvironment in crater lake Barombi Mbo, Cameroon, during the last 25,000 years

Sedimentary Geology, Vol 71(3-4), page(s) 151-175

Egbe, A.M., Tabot, P.T. & Ambo, F.B., 2021

Tree Species Composition and Diversity in the Riparian Forest of Lake Barombi Kotto, Cameroon

American Journal of Plant Sciences, Vol 12, page(s) 127-145

Cheek, M. & Lovell, R., 2020

Combretum exellii. The IUCN Red List of Threatened Species 2020: e.T110096585A110096588

Available online

Cheek, M. & Thulin, M., 2015

Dielsantha galeopsoides. The IUCN Red List of Threatened Species 2015: e.T45438A3002804

Available online

Lovell, R. & Cheek, M., 2020

Acridocarpus staudtii. The IUCN Red List of Threatened Species 2020: e.T110082209A110082211

Available online

Cheek, M. & Lovell, R., 2020

Rhaphiostylis poggei. The IUCN Red List of Threatened Species 2020: e.T110089751A110089753

Available online

MINFOF (Ministry of Forestry and Wildlife) & WRI (World Resources Instiute), 2021

Forest Atlas of Cameroon

Available online

Recommended citation

Bruce Murphy, Martin Cheek (2024) Tropical Important Plant Areas Explorer: Lake Barombi Mbo Forest Reserve (Cameroon). https://tipas.kew.org/site/lake-barombi-mbo-forest-reserve/ (Accessed on 21/05/2024)