Mount Bamboutos

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

Mount Bamboutos potentially qualifies as an IPA on the basis of past collections of multiple threatened species. However, it is not known if most of these still survive in the area and if they do it is likely to be so in the western part and the caldera, or perhaps in remnant hedges and forest fragments. Herbaceous species are more likely to survive in grassland and scrubby areas on the eastern side.

Mount Bamboutos is located at the juncture of West, Southwest and Northwest regions, Cameroon. It is the third highest point in the country after Mount Cameroon and Mount Oku, and like those peaks it is part of the Cameroon Line of volcanoes which extends northwest from the Gulf of Guinea and continues beyond Mount Bamboutos as the Bamenda highlands. The area identified here lies within West and Southwest Regions, with a huge caldera at the centre. To the north, south and east the land slopes away gradually from the rim of the caldera forming a high plateau that is heavily populated and cultivated. The western side is much steeper and more forested, dropping rapidly 2.5 km in height to the valley below. The proposed area is a preliminary demarcation based on historical records of botanical significance. Further surveys and consultation will be required to demarcate an actual area where important taxa remain amidst the mostly degraded landscape.

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Mount Bamboutos and the neighbouring plateau has been a focus for Western botanical collecting since the nineteenth century and there are many records of species which are now threatened with extinction. However, it is also one of the most populated areas of Cameroon and has been densely grazed and farmed with extensive loss of forest. Most of the historically recorded taxa were collected from areas that now have no forest remaining, only hedges and patches of trees and savannah (Cayet-Boisrobert, 2020). It is not known how many of these species survive in this fragmented habitat or in the remaining forested parts on the western side. The exceptionally rare, critically endangered and medicinal plant, Ternstroemia cameroonensis, originally collected at this site by Letouzey, is currently thought to only survive at one location within this site, having apparently become extinct at Mt Oku (Cheek et al., 2017). Vepris montisbambutensis (CR) is known only from the type collected here in 1974. Clerodendrum singwanum is known only from the Ledermann collections in 1908 probably lost in the Berlin herbarium fire.

The upper slopes of Mount Bamboutos, constituting the area under consideration, are dominated by acidic volcanic rocks such as trachytes, phonolites, rhyolites and tuffs. (Ngoufo, 1992). Soils are generally acidic but varied, with widespread lithosols and rankers but also fertile soils rich in dark humus (Ngoufo 1992). Although these highlands soils have been worked for agriculture for far less time than the lower plateau, they are highly vulnerable to erosion and leaching due to the steep gradients, high precipitation and loss of vegetation (Ngoufo 1992).
Precipitation probably varies considerably across the site due to altitude and the rain shadow effect. Mean annual precipitation at Bamenda to the north was 2260 mm between 1971-2000 (WMO, 2020) but at Dschang, south of the summit, was 1873 +-209 mm between 1910 and 2000 (Kengni et al., 2009). Both these stations are around 1400 m below the summit of Mount Bamboutos. Kengni et al. (2009) recorded a total of 2507 mm over 1 year (2002-3) at the Mélétan station (2608 m). Precipitation is strongly seasonal, with the steep western slopes intercepting the humid Atlantic monsoon winds; 75% of annual precipitation occurs between June and October, and 50% between July and September (WMO, 2020; Ngoufo, 1992). November, December and January are the driest months, with virtually no rain falling in some areas in the east (Ngoufo, 1992). Mean temperatures vary relatively little at lower altitudes (e.g. Bamenda max 22.1-26.8 °C, min 13.1-16.7 °C) but even at 2000 m morning temperatures may drop to zero °C in the dry cold months of November-February.
While probably originally forested, the high Bamboutos area has long borne the imprint of human civilisation. Colonial era maps suggest livestock grazing resulted in savanna of trees or shrubs as well as areas of grassland, with forest remaining only in valleys, steep slopes and along rivers (Ngoufo, 1992; Cayet-Boisrobert, 2020). However, since the 1970s, increasing population pressure and impoverishment of soils in the piedmont area, as well as opportunities for cash crops suited to higher altitude, have led to cultivation and further loss of semi-natural vegetation even at high altitudes, with increased pressure on reduced area of grazing lands, increased fire, and soil erosion from cultivation of even steep slopes (Ngoufo, 1992; Tchassem et al 2019).

There has been almost complete loss of forest on the northern and eastern slopes of Mount Bamboutos under intense agricultural and population pressure (Ngoufo, 1992; Cayet-Boisrobert, 2020; Tchassem et al., 2019). While it is possible that threatened tree species hang on in hedges or isolated clumps, the extent of development, with large settlements visible on the summit rim itself at 2600 m, make conservation very challenging on this side of the mountain. The small Mount Bamboutos Forest Reserve was already fully degraded from forest to savanna vegetation by 1957 (Cayet-Boisrobert, 2020). Patches of forest are visible still on satellite imagery (Google Earth, 2020 – most recent images April 2020) and may represent small areas that could be considered a salvageable IPA but ground truthing is rapidly required to assess these.
Fire, grazing, agricultural cultivation and soil erosion, including landslides are the main conservation issues. Conflicts exist between traditional livestock grazing and subsistence farming at high altitudes by mainly Fulani (Mbororo) peoples and upwards pressure from Bamilike Mbouda groups growing a new diverse range of garden cash crops such as carrots, cabbage and potatoes as well as oil palm and cocoa (Ngoufou, 1992; Tchassem et al., 2019; Toh et al., 2018). Cultivation of steep slopes, shortened fallowing, increased fire and loss of natural vegetation has resulted in rapid loss of previously fertile, humus-rich high altitude soils and major landslides. Even on the south western slopes and within the caldera valley, there is alarming loss of hitherto better preserved forest with associated erosion and landslides (Toh et al., 2018).
Mount Bamboutos is also a major watershed and habitat conversion and irrigation has resulted in drying up of streams while pollution, sedimentation and nutrient enrichment also result from the intense agricultural use of the land (Ngoufo, 1992; Cayet-Boisrobert, 2020).
The NGO ERuDeF is active in the area and has instigated tree-planting including native species such as Prunus Africana which was eliminated through over-harvesting in the 1990s (Greenvision, 2020). The organisation also promotes more sustainable agricultural methods, hydrological conservation, sustainable income generation and habitat corridors (Cayet-Boisrobert, 2020). Restoration work and surveying is also being funded by ZSL EDGE, focused particularly on amphibians and reptiles, and by the International Tree Foundation (T. Doherty-Bone, 2022, pers. comm. 4 Jan).

Over 80,000 people are estimated to be dependent on the watershed, as well as two major hydroelectric plants (Cayet-Boisrobert, 2020). Natural vegetation plays a crucial role in protecting watersheds, reducing soil erosion and sedimentation and protecting against landslides. Habitat restoration has been advocated for these reasons (Ntasin et al., 2008)
The area was considered a very important area for birds although these are now probably limited largely to the western part which is also important habitat for various mammals including gorillas and chimpanzees (Tchassem et al., 2018; International Tree Foundation, 2020; Nkembi et al., 2006).
Forests, where they still exist, also provide various products including medicines to local people (Fotso et al., 2018; Tchassem et al., 2018).

Bruce Murphy, Royal Botanic Gardens, Kew

Jean Michel Onana, University of Yaounde I, Faculty of Science, Department of Plant Biology; IRAD-Herbier National Camerounais