Mount Vokré

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

Mount Vokré qualifies as an IPA under criterion A(i) through its important populations of several globally threatened species, most notably Antherotoma clandestina (EN), Crotalaria ledermannii (VU) and Ledermanniella raynaliorum (EN).

Mount Vokré in North Region, Cameroon, is a horseshoe shaped mountain ridge reaching nearly 2000 m. It lies 100 km south of Garoua and a few km south of the town of Poli, and between Faro and Benoué National Parks which are of predominantly low altitude. As well as the summit, several additional peaks in the range are named, including Hosere Kogo and Hosere Mango. To the Northwest, narrowly separated by a 300-400 m valley a related peak, Hosere Gode rises to 1600 m and is included here. A smaller separated peak, Hosere Poli, also rises to nearly 1000 m on the eastern edge of Poli itself but is excluded. To the east the range forms a plateau which slopes away gradually. The proposed boundary is a tentative suggestion and surveying is required to indicate what parts retain conservation value.

These mountains have seen a fairly high number of collections compared to elsewhere in the North, Far North and Adamawa regions but there are no recent records of the more notable taxa. G. Fotius, J & A Raynal, H Jaques-Felix, C. Geerling and A.P.M Van der Zon are responsible for most of the collecting and important records which date from the 1960s-1980s. A large number of non-vouchered observations by Le Bourgeois in 1990 and OUSTALET in 2003 do not appear to have returned rare or threatened taxa.
Antherotoma clandestina (EN) is endemic to Adamaoua region and only recorded at one other nearby site, Mt Nganha, while Ledermanniella raynaliorum (EN) is only otherwise recorded from a single site in Nigeria (Cheek, 2015; Cheek & Lovell, 2021). Rhynchosia ambacensis subsp. cameroonensis (provisionally EN, Onana & Cheek, 2011) is also very rare. Other species such as Wahlenbergia ramosissima subsp. ramosissima and Panicum acrotrichum are somewhat more widely recorded but still assessed as Vulnerable. Mount Vokré is also notable for hosting outlier populations of taxa otherwise limited to Northwest and Southwest regions of Cameroon, such as Crotalaria ledermannii (VU) a national endemic, and Podocarpus milanjianus. The remarkable orchid Ansellia africana (VU), although widespread in Africa, has rarely been scientifically recorded in Cameroon but twice collected at this site. It is threatened by horticultural and ethnobotanical collecting (Crook, 2013). Echinops mildbraedii is provisionally assessed as NT by Onana & Cheek (2011). Thesium equisetoides (NE) also has a large range across Africa but is very sparsely recorded and is only known in Cameroon from this site.
In addition, several other taxa are recorded from nearby Hosere Godé, including narrow endemic Eugenia poliensis, Cyphostemma leucotrichum (provisionally EN), Globimetula oreophila (VU in Onana & Cheek, 2011 but now more widely recorded), Dombeya ledermannii (CR), Vernonia chapmannii (provisionally VU) and Vitex bogalensis (Not Evaluated).

Mount Vokré is in the Central African Fold Belt region, a zone between the Congo Craton, the West African Craton and the Chad basin. The mountains are formed of Neoproterozoic granitoids, uplifted as a horst like structure and surrounded by metabasalts and micaschists (Kouske et al., 2012; Essi et al., 2017; Thiéblemont et al., 2021). Many large granite boulders, forming deep crevices, are exposed at the summit area and found in gallery forest at slightly lower altitudes (Bauer et al., 2006). One of only two known Cameroon uranium deposits (the Kitongo occurrence) is known from the northwestern margin and occupies an area of ~ 1.8 km by ~ 1.3 km (Kouske et al., 2012). The higher altitude areas are characterised by leptosols, with gleyic luvisols and planosols in the lower areas to the west, and ferric luvisols and regosols to the east (Yerrima & Van Ranst 2005; Letouzey, 1982).
Average annual precipitation at Poli (478 m) is 1352 mm. There is a single wet season (Koppen type: Aw) running from mid March to the end of October and peaking in August (275 mm, humidity 80%). Very little rain (<=5mm) falls from November to February. Average annual temperature is 24 °C, with January being the coolest month (average 21.4 °C) and temperatures peaking in April (average 27.6 °C) as the rains build (WeatherBase, 2022).
Letouzey (1982) maps the main ridge as vegetation type 119, a strongly degraded submontane forest of Guineo-Congolian type, sometimes colonised by thorny trees. The highest region is mapped as type 113, mountain pastures with Sporolobus africanus and forest galleries, and at this altitude Letouzey (1982) comments on similarity with the rest of the Cameroon Line mountains. Lower slopes consist of mainly type 66, "Mid-Sudanian wooded savannas with Isoberlinia doka, sometimes degraded, on rocky soils; sometimes stands of Isoberlinia doka as open dry forests", although a considerable area at lower altitude is uncategorised, perhaps indicating anthropic degradation. Groves of Borassus aethiopum are cultivated around Poli and Hosére Godé. The Main forest trees are Syzigium guineensis and Phoenix reclinata (Larison et al., 1996; Bauer et al., 2006).

The area has a high population density and impacts on the natural habitat have been described as "extremely high" (Larrison et al. 2000). Forest is largely limited to narrow gallery forests in valleys and gorges with dry wooded savanna in between. The summit area appears largely bare. It is assumed that forest cover was formerly much more complete although perhaps not reaching the highest regions. Grazing is likely to be the main cause of degradation (Cheek, 2015). Pastoral villages and cattle grazing are reported on the plateau itself, with streams used for watering livestock. There is also cultivation of the lower slopes and even on the plateau. Fire is not mentioned but is likely to be used to rejuvenate grazing land, and fuelwood gathering is likely a further impact. Numerous fire alerts are indicated over the latest month (prior to 18/03/2022) by infrared satellite imaging using a 375 m pixel size (NASA FIRMS, 2022). Gallery forests are targeted for both grazing, particularly in the dry season, and for cultivation because of the moister soils (Bauer et al., 2006). One of the globally threatened and narrowly endemic species, Ledermannia raynaliorum is a rheophytic species from waterfalls and rapids and likely to be susceptible to impacts on these streams (Cheek & Lovell, 2021).
Hidden crevices between the large granite boulders may shelter surviving populations of important species.
The Kitongo uranium deposit is thought to contain up to 13,000 tonnes of ore material but is of low value (IAEA, 2009). Drilling in 2010 by Mega Uranium Ltd revealed nothing of economic significance. Further drillling in 2011 was defered and does not appear to have resumed (KPMG, 2014). A large area, extending through Benoué National Park remains under various mining permits (MINFOF & WRI, 2020).

The site is one of only three locations for Vepris oubanguiensis, which is widely used as a remedy for asthma and cough. Phytochemical research has isolated novel chemical compounds from samples of this species collected on Mount Vokré (Ayafor et al.,1982, 1986). Other medicinal and edible species are recorded and are likely to be highly utilised by local people.
The remaining gallery forest protects the streams and rivers that provide fresh water to local communities including Poli. Denser forest may have previously intercepted and condensed atmospheric moisture at high elevations, increasing total precipitation, suggesting restoration may have benefits for water supply.
A species of Gecko, Cnemaspis alantika (EN) is narrowly endemic to Mount Vokré and the nearby Atlantika mountains (Bauer et al., 2006; LeBreton et al., 2021). Ninety-one bird species have been recorded, three of which were at their most northern recorded site (Larison et al., 2000), although none were rare and few forest species were found. The spider Malinella vokrensis appears to be narrowly endemic to the site (Bosmans & Van Hove, 1986; World Spider Catalog,2022).

Bruce Murphy, Royal Botanic Gardens, Kew