Mont Kala

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

Mount Kala qualifies as an IPA on the basis of several globally threatened species which are present here and at few other locations, including some that are endemic to the site or the wider Yaounde area.

Mont Kala is an east-west oriented ridge approximately 7 km in length located about 20 km west of Yaoundé. It is part of the chain of prominences located between the main N3 and N3A roads running into Yaoundé from the west which form the southern section of the steep topography flanking the western side of Yaoundé. The ridge is mostly around 900–950 m high with several summits rising to over 1,000 m.

Many botanical collections were made in the Yaoundé area by Zenker and Staudt in the 1890s (Cheek et al., 2011). While unfortunately most of these can not be precisely located, the western hills are the main surviving areas where some natural habitat remains. These are forested inselbergs and provide an interesting flora differing from the lower surrounding areas. Subsequent collecting has recorded several globally threatened species from these hills, including Mount Kala which is one of the least degraded due probably to its greater distance from the centre of Yaoundé. In particular, two species of Afrothismia are currently considered endemic to Mount Kala. Pavetta bidentata var. sessilifolia is also considered endemic to Mount Kala and the Kombing area 30 km to the Southwest. Disperis aphylla (VU) appears to be only recorded in Cameroon from this site. Gastrodia africana is a very rare and little understood species which was apparently collected at Mount Kala in 1968 (although the specimen appears to be missing) and from one or two other locations. Other species such as Callichila monopodialis (VU), Tricalysia amplexicaulis (provisionally VU, Onana & Cheek, 2011), T. atherura (VU) and Culcasia sanagensis (VU) are mainly known from here and other hills in the Yaoundé area.

The hills around Yaoundé rise from the South Cameroon plain between the Sanaga fault and the north-thrusting Congo craton. They are formed from high grade metamorphic rocks, mainly granulites and migmatites also referred to as embrichite gneiss (Achoundog, 1985), formed from sedimentary and igneous protoliths and apparently dating from around 600 mya (Nzenti, 1988; Tchouatcha et al., 2018; Ngnotue et al., 2012). The soils and topology of these hills are often unstable and susceptible to catastrophic landslips (Zogning et al., 2007).
Precipitation in Yaoundé is 1,605 mm per annum, falling in a bimodal pattern with a small (March-June) and greater (September-November) wet season interspersed with a drier period (July-August) and a second more severe dry period between December and February when mean monthly rainfall drops below the relatively flat mean monthly temperature curve (range: 2.8–25.47 °C) on a Walter-Leith type chart (Simo et al., 2009; Bissaya et al., 2014; Noumi, 2015). This is below the level of rainfall normally thought necessary to sustain evergreen tropical forest (Cheek et al., 2011), although the level maybe higher on the summits with orographic precipitation likely (Noumi, 2015; Simo et al., 2009). Achoundong (1985) describes the vegetation as semi-deciduous although the lower altitudes are largely cultivated and even up to the highest altitude there is cultivation and wood extraction (Mbenoun Masse & Makon, 2019).
Madiapevo et al. (2017) describe the summit forest as diverse and having affinities with other West African submontane forest but with high representation of Clusiaceae and Cola. Common species included Allanblackia gabonensis, Tabernaemontana crassa, Santiria trimera, Ceolocaryon preussii, Pycnanthus angolensis, Cola attiensis var. bodardii and Aulacocalyx jasmiflora.

Yaoundé was the second largest city in Cameroon at the last census but has been estimated to be growing at over 5% per year. It is now estimated to have the largest population in the country and is predicted to reach 5.7 million by 2030 (United Nations, 2018). All of the western hills and areas of vegetation have been seriously degraded or lost due to small scale agriculture, suburban spread, hotel development, extraction of timber and quarrying. Mount Kala is one of the furthest from the centre but has not escaped habitat loss at all altitudinal levels. Clearance for agriculture and logging has particularly impacted the slopes up to 1,000 m, with cleared areas easily visible on satellite imaging. A road has been bulldozed from the base of the site as far as the rock cliff and land is being sold off (R. Fotso, 2021, pers. comm, 9 June).
The site is included in the Mbam Minkom-Mount Kala Important Bird Area (Bird Life International, 2020) and in 2009 Mount Kala was considered the only other remaining nesting site in the Yaoundé area for Picathartes oreas (VU) other than the larger Mbam Minkom massif (Awa II et al., 2009).

The hills around Yaoundé are unstable and therefore remaining forested vegetation is important in preventing landslips which have claimed lives and caused damage such as the Oyom Abang landslide in western Yaoundé in September 1990 which killed five people (Zogning et al., 2007; Mukenga et al., 2016). In a rapidly growing metropolitan area such sites are also an important recreational and educational resource for the growing population and the survival of rare species and primary vegetation greatly increases the value of such sites. For example, the many important and threatened timber species are known from the site, make them useful for students studying forestry or biodiversity at the Yaoundé universities and for informing the public about the country's natural heritage.
The site provides habitat to threatened bird species such as Picarthes oreas (VU).

Bruce Murphy, Royal Botanic Gardens, Kew

Xander van der Burgt, Royal Botanic Gardens, Kew

Dr Vincent Droissart, Institute of Research for Development. Marseille

Professor Bonaventure Sonke, University of Yaounde I