Mount Ngang-Ha

Tchabal Ngangha, Mont Ngao-Ha, Gangha Gebirge, Mont Gangha, Mont Ganhoua, Mont de Ganga

CMNTIPA044
Mount Ngang-Ha

Country: Cameroon

Administrative region: Adamawa (Region)

Central co-ordinates: 7.35910 N, 14.00260 E

Area: 128km²

Qualifying IPA Criteria

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

IPA assessment rationale

The site qualifies as an IPA under criterion A(i) through the presence of several globally threatened taxa that occur at few other sites.

Site description

Mount Nganha is an inactive strato-volcano rising to nearly 2000 m above the Adamawa Plateau. It lies 45 km east of Ngaoundéré, in the Adamawa region. A road runs as far as the settlements of Ndigou and Nganha at the western foot of the mountain. The mountain area designated here encompasses about 100 km2 from where it starts to rise up from the more gradually sloping 1200-1300 m plain. To the east and southeast, however, the terrain slopes away less abruptly. The site is mainly covered in sparsely wooded savanna, with ribbons of gallery forest descending. The summit rim ("Doïtaïa Mounts") features very steep, rocky terrain enclosing on south, east and west sides a 3 km wide caldera which opens to the north. Volcanic plugs are also prominent at the base of the mountain on both east and west sides.

Botanical significance

The site is significant for Antherotoma clandestina (EN), only otherwise recorded from Mt Vokre, and Trifolium gillettianum (EN) which is known only from the type specimens collected somewhere in the area, probably on the southern or eastern slopes. Cassipourea adamauensis has yet to be evaluated but is only recorded from this site. Crotalaria mentiens (EN) is only otherwise known from 2 sites in the Bamenda Highlands. Platycoryne alinae (EN) is known only from one other collection at nearby Tello Falls. Dolichos reptans (EN) is also very rare, known only from 5 other collections, all but one from the Adamawa Plateau. Hypoxis suffruticosa (VU) is only known in Cameroon from this site (and close by) and a few records in the area of Tchabal Mbabo. Humularia ledermannii is assessed as DD but is only known from 4 nearby locations with no recent collections. Hygrophila mediatrix (EN) grows nearby at Mare de Tourningal and at Tello Falls and could also occur at this site in lower lying, marshy areas. Mount Nganha is also the type location of Phaulopsis symmetrica, which is not IUCN assessed but known from only a few other locations extending to the Bamenda Highlands and Mambilla Plateau in Nigeria. Podocarpus latifolius also occurs here; it is rare in Cameroon and the Adamawa population is apparently part of a genetic phylogroup limited to Cameroon (Migliore et al., 2020). Otiophora villicaulis is another species not considered globally threatened but, apart from one other nearby collection in Adamawa, only otherwise recorded over 2000 km away in East Africa, Zambia and southern DRC. Pachycarpus medusonema (EN) has been recorded at locations east, west and south of Nganha and therefore may also occur.
Although many of these species have not been recorded since the 1960s, a number of collections were made at the site in 2011, including Podocarpus latifolius, Otiophora villicaulis, Crotalaria mentiens (EN), Pavetta lasioclada (VU) and Dissotis longisetosa (NT) in " in well-preserved mountain forests (due to very rugged topography)" (V. Droissart, pers. comm., 7 July, 2020).

Habitat and geology

Mount Nganha is a large, Mioecene-Pliocene, intra-plate stratovolcano sitting on top of the precambrian basement rocks of the uplifted Adamawa plateau. The surface rocks are 87% basalts, while brescias, phonolites and trachytes are also prominent. The terrain is often very steep, with gallery forest in narrow gorges.
There is a two-season, savannah climate (Kppen type Aw). At Ngaoundere (1114 m), annual precipitation is 1511 mm which falls almost entirely in a wet season which runs from late March to the end of October, peaking in August with 270 mm. Average monthly temperatures (21-23 °C) vary little across the year, while average monthly lows vary from 12 to 17 °C and monthly high temperatures are 25-31 °C (Weatherbase, 2022).
The predominantly savanna vegetation is presumably strongly influenced by anthropic effects, namely nomadic Fulani grazing and seasonal burning (Larison et al., 2000). On Letouzey's (1982) maps it is predominantly type 128 (more or less grazed and inahabited submontane meadows and fallows with gallery forests), while the higher parts from 1600 m are type 113 (Sporolobus africanus montane pasture with gallery forests).

Conservation issues

Grazing, wood gathering and burning are the primary concerns for the survival of the key taxa (Larison et al., 2000; Cheek, 2015ab; IUCN SSC Amphibian Specialist Group, 2019; NASA FIRMS, 2022). Forest is largely confined to narrow valleys. However, the rugged terrain has preserved these patches of forest better than might otherwise be expected. There is little sign of inhabitation or cultivation of the slopes, although a large network of farms can be seen on the flatter land around Nidigou and some of the threatened species, including the endemic Trifolium gillettianum occur at low enough altitudes to be potentially affected. Trampling and muddying of watercourses are also threats to some species (Cheek, 2015abc).
The site is designated a KBA and Zero Extinction Alliance status due to the trigger species, Astylosternus nganhanus (KBA Partnership, 2022; AZE, 2022). However, there is no official protection or obvious conservation involvement. Violence and kidnapping associated with the Boko Haram movement, and the Central African Republic civil war, has made the site a security risk and is likely to limit involvement by conservation agents (V. Droissart, pers. comm., 7 July, 2020).

Ecosystem services

The gallery forests provide habitat for the Critically Endangered and narrowly endemic Mount Nganha Night Frog (Astylosternus nganhanus; IUCN SSC Amphibian Specialist Group, 2019). The forested gorges also likely contribute to buffering rains and maintaining water quality for the villages lower down the slopes. The spectacular volcanic terrain makes the site a visitor attraction, and together with the nearby Tello Falls, Vina Falls and Lake Tison part of a potential tourist route for those drawn to Benoué or Mbere Valley national parks.

Site assessor(s)

Bruce Murphy, 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
Antherotoma clandestina Jacq.-Fél. A(i) True True True False False
Platycoryne alinae Szlach. A(i), A(iii) True True True False False
Dolichos reptans Verdc. A(i) True True True False False
Wahlenbergia ramosissima (Hemsl.) Thulin subsp. ramosissima A(i) True False False False False
Globimetula oreophila (Oliv.) Tiegh. A(i) True False False False False
Trifolium gillettianum Jacq.-Fél. A(i) True True True True False
Pavetta lasioclada (K.Krause) Mildbr. ex. Bremek. A(i) False True True False False
Hygrophila mediatrix Heine A(i) False False False False False
Crotalaria mentiens Polhill A(i) True True True False False
Pachycarpus medusonema Bullock A(i) False False False False False
Hypoxis suffriticosa Nel A(i) True True True False False
Cassipourea adamauensis Jacq.-Fél. ex A(iii) True True True True False

Antherotoma clandestina Jacq.-Fél.

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:

Platycoryne alinae Szlach.

Qualifying sub-criterion:
A(i), A(iii)
≥ 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:

Dolichos reptans Verdc.

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:

Wahlenbergia ramosissima (Hemsl.) Thulin subsp. ramosissima

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:

Globimetula oreophila (Oliv.) Tiegh.

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:

Trifolium gillettianum Jacq.-Fél.

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:

Pavetta lasioclada (K.Krause) Mildbr. ex. Bremek.

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:

Hygrophila mediatrix Heine

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

Crotalaria mentiens Polhill

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:

Pachycarpus medusonema Bullock

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

Hypoxis suffriticosa Nel

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:

Cassipourea adamauensis Jacq.-Fél. ex

Qualifying sub-criterion:
A(iii)
≥ 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:

General site habitats

General site habitat Percent coverage Importance
Shrubland - Subtropical/Tropical High Altitude Shrubland No value
Rocky Areas - Rocky Areas [e.g. inland cliffs, mountain peaks] No value
Forest - Subtropical/Tropical Moist Montane Forest No value

Shrubland - Subtropical/Tropical High Altitude Shrubland

Percent coverage:
No value
Importance:

Rocky Areas - Rocky Areas [e.g. inland cliffs, mountain peaks]

Percent coverage:
No value
Importance:

Forest - Subtropical/Tropical Moist Montane Forest

Percent coverage:
No value
Importance:

Land use types

Land use type Percent coverage Importance
Harvesting of wild resources No value Unknown
Agriculture (pastoral) No value Major

Harvesting of wild resources

Percent coverage:
No value
Importance:
Unknown

Agriculture (pastoral)

Percent coverage:
No value
Importance:
Major

Threats

Threat Severity Timing
Agriculture & aquaculture - Annual & perennial non-timber crops - Small-holder farming Low Ongoing - trend unknown
Biological resource use - Logging & wood harvesting Medium Ongoing - trend unknown
Agriculture & aquaculture - Livestock farming & ranching - Nomadic grazing High Ongoing - trend unknown
Natural system modifications - Fire & fire suppression - Increase in fire frequency/intensity High Ongoing - trend unknown
Human intrusions & disturbance - War, civil unrest & military exercises Unknown Ongoing - trend unknown

Agriculture & aquaculture - Annual & perennial non-timber crops - Small-holder farming

Severity:
Low
Timing:
Ongoing - trend unknown

Biological resource use - Logging & wood harvesting

Severity:
Medium
Timing:
Ongoing - trend unknown

Agriculture & aquaculture - Livestock farming & ranching - Nomadic grazing

Severity:
High
Timing:
Ongoing - trend unknown

Natural system modifications - Fire & fire suppression - Increase in fire frequency/intensity

Severity:
High
Timing:
Ongoing - trend unknown

Human intrusions & disturbance - War, civil unrest & military exercises

Severity:
Unknown
Timing:
Ongoing - trend unknown

Conservation designation

Designation name Protected area Relationship with IPA Areal overlap
Mont Nganha Key Biodiversity Area protected/conservation area overlaps with IPA No value
Mont Nganha Alliance for Zero Extinction Site protected/conservation area overlaps with IPA No value

Mont Nganha

Protected area:
Key Biodiversity Area
Relationship with IPA:
protected/conservation area overlaps with IPA
Areal overlap:
No value

Mont Nganha

Protected area:
Alliance for Zero Extinction Site
Relationship with IPA:
protected/conservation area overlaps with IPA
Areal overlap:
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.

AZE, 2018

Alliance for Zero Extinction 2018 Global AZE map.

Available online

Larison, B., Smith, T.B., Fotso, R. & McNiven, D., 2000

Comparative avian biodiversity of five mountains in northern Cameroon and Bioko

Ostrich, Vol 71(1 & 2), page(s) 269-276

Cheek, M., 2015

Antherotoma clandestina. The IUCN Red List of Threatened Species 2015: e.T202774A2752585

Available online

NASA FIRMS, 2022

“VIIRS Active Fires.” Accessed through Global Forest.

Available online

Migliore, J., Lézine, A-M. & Hardy, O.J., 2020

The recent colonization history of the most widespread Podocarpus tree species in Afromontane forests

Annals of Botany, Vol 126(1), page(s) 73–83

Weatherbase, 2022

Climate summary: Ngaoundere, Cameroon

Available online

Cheek, M., 2015

Dolichos reptans. The IUCN Red List of Threatened Species 2015: e.T202753A2750866.

Available online

IUCN SSC Amphibian Specialist Group, 2019

Astylosternus nganhanus. The IUCN Red List of Threatened Species 2019: e.T54420A95847037

Available online

Nono, A., Déruelle, B., Demaiffe D. & Kambou, R., 1994

Tchabal Nganha volcano in Adamawa (Cameroon): petrology of a continental alkaline lava series

Journal of Volcanology and Geothermal Research, Vol 60(2), page(s) 147-178

Key Biodiversity Areas Partnership, 2022

Key Biodiversity Areas factsheet: Mont Nganha. Extracted from the World Database of Key Biodiversity Areas. Developed by the Key Biodiversity Areas Partnership: BirdLife International et al.

Available online

Recommended citation

Bruce Murphy (2024) Tropical Important Plant Areas Explorer: Mount Ngang-Ha (Cameroon). https://tipas.kew.org/site/mount-ngang-ha/ (Accessed on 27/05/2024)