Kambui Hills

A(i)Site contains one or more globally threatened species, C(iii)Site contains nationally threatened or restricted habitat or vegetation types, AND/OR habitats that have severely declined in extent nationally

This site has been assessed under criteria A and C, with a total of 25 globally threatened species and a nationally restricted habitat occurring within this IPA.

The Kambui Hills IPA lies directly west of the adjacent town of Kenema, and straddles both the Eastern and Southern Districts of Sierra Leone. This IPA contains important remnant patches of lowland forest habitat, now primarily constrained to hill slopes at the site. This site consists of two distinct areas that are bisected by the Kenema-Bo Highway, referred to as the ‘Northern’ and ‘Southern’ patches. The highest peak at the Kambui Hills is an unnamed hill in the Northern patch that rises to 646 m a.s.l. The western side of the hills drains into the Waanje River, while the streams on the eastern side of the range drain into the Moa River, which borders the IPA to the east. This IPA overlaps with the Kambui Hills Forest Reserve (KHFR).

The Kambui Hills are one of the last refuges for lowland forest species in Sierra Leone. Notably, this site is a globally important reserve for Coffea stenophylla (Highland Coffee) subpopulations, as one of the last two sites globally where this species is known to occur in the wild.
Moist closed forest and gallery forest at the site is known to contain threatened tree species such as Brachystegia leonensis (VU), Cola angustifolia (EN), Cola simiarum (VU), Dactyladenia globosa (EN), Drypetes afzelii (VU) and Tessmannia baikiaeoides (VU). Coffea stenophylla (VU) occurs in drier areas such as exposed slopes and ridges at the site, while swamp forest contains Homalium smythei (VU). Cryptosepalum tetraphyllum (VU) and Leptonychia occidentalis (VU in draft) have broader habitat requirements and can occur in both primary and secondary forest (Savill & Fox 1967). Tarenna hutchinsonii (CR), a shrub or small tree of high conservation importance for this IPA, is only found in undisturbed moist closed forest. T. hutchinsonii (Rubiaceae) was collected at Kenema in 1914 (Thomas #7536) but has not been observed at this locality or elsewhere in Sierra Leone since, thus further targeted surveys for T. hutchinsonii in Sierra Leone at this site are recommended. The species has since been found in neighbouring Guinea. While there are some other records of threatened species from this IPA, many of these are widely distributed timber species that are of comparatively low conservation priority (Afzelia africana, Copaifera salikounda, Entandrophragma cylindricum, Entandrophragma utile, Garcinia kola, Guibourtia copallifera, Lophira alata, Milicia regia, Terminalia ivorensis, Tieghemella heckelii and Turraeanthus africanus). It is likely that additional species of conservation importance will be found in future surveys.

The Kambui Hills IPA contains remnant moist closed forest, with microhabitats such as evergreen forest, semi-deciduous forest, freshwater swamp forest and gallery forest present at the site (Lebbie 2024). The canopy is diverse and mostly constituted of evergreen species, with lianas, epiphytes and ferns also common (Savill & Fox 1967, Cole 1968, Konteh 1997). Semi-deciduous tree species are scattered throughout the site corresponding to locally dryer topographic or edaphic conditions (Senterre et al. 2020). Where the forest has been cleared, vegetation at various successional stages occurs, from ‘farmbush’ to thicket and young secondary forest (Cole 1968). Other intensive disturbances have led to the collapse of forest ecosystems, with such land use categories including palm oil plantations and rice crops. As the site reaches above 500 m a.s.l., threatened submontane forest habitat may also occur at the ‘Northern’ patch, however this habitat has not yet been observed at the site.
The Kambui Hills consist of steep hilly outcrops of metamorphic rocks known locally as the "Kambui schists", scattered over the predominantly Precambrian granitic landscape (Odell et al. 1974). The lithology of the site is rare and features mafic-ultramafic rocks with a zone of interbanded serpentinised dunite and chromite, with smaller areas of metasedimentary rocks include biotite gneiss, quartzite and banded iron formations (Goodenough et al., 2018).
The Kambui Hills consist of steep hilly outcrops of metamorphic rocks known locally as the "Kambui schists", scattered over the predominantly Precambrian granitic landscape (Odell et al. 1974). The lithology of the site is rare and features mafic-ultramafic rocks with a zone of interbanded serpentinised dunite and chromite, with smaller areas of metasedimentary rocks include biotite gneiss, quartzite and banded iron formations (Goodenough et al., 2018).

The Kambui Hills, one of Sierra Leone's oldest forest reserves, was gazetted in 1920 and has experienced significant environmental pressures over the decades, particularly from timber activities between 1930-1970 (Senterre et al. 2022, Munro 2012a). Although periods of unrest, including the civil war (1991-2002) and the Ebola pandemic (2013-2016) temporarily increased forest cover (Munro 2012b); post-COVID-19 logging and clearing activities have surged (A. Davis pers. comms. 2024). Current threats to this IPA include logging, illegal diamond and gold mining, artisanal mining (GoSL 2024), quarrying for construction materials, charcoal production and agricultural encroachment, which have significantly degraded the ecosystem and reduced natural habitats. The ‘Southern’ portion of the site is particularly impacted by such anthropogenic activities (Lebbie 2024). While the Northern patch is relatively intact, construction of houses in areas that were once part of the northern reserve have accelerated in recent times (Lebbie 2024). Additionally, Coffea stenophylla subpopulations at the site are at significant risk due to unsustainable harvesting of seedlings (Lebbie 2023). Within the Kambui Forest Reserve there are ongoing governance challenges and unresolved boundary conflicts which hinder effective management and enforcement at the site (Munro 2012b, Adamu Mboma 2021, Lebbie 2024). Urgent conservation measures are needed to safeguard the remaining biodiversity and ecological integrity of this IPA.

This IPA acts as a refuge for the biodiverse native flora and fauna that inhabit the region (Munro 2012a, BirdLife 2020, KBA 2024). This includes Coffea stenophylla, a threatened species of potential significance for future coffee cultivation (Davis et al. 2020). This IPA holds remaining wild populations and is a vital genetic reservoir of this species. Additionally, this site provides livelihoods for neighboring communities through harvesting resources such as charcoal, timber and highland coffee propagules and exploitable natural resources such as plant medicines, wild animal meat and materials (Senterre et al. 2022, Lebbie 2024). The Kambui Hills serve as a vital catchment area, providing potable water to Kenema and surrounding communities. Furthermore, the native vegetation present at the site contributes to erosion control and is an important carbon sink.

Gabriella Hoban, Royal Botanic Gardens, Kew

Aiah Lebbie, The University of Sierra Leone

Momoh Plato Sesay, The National Herbarium of Sierra Leone

Samuel Sokpo, Eastern Technical University

Fanny Massally, Njala University College

Date of first assessment: 13th Dec 2024

Xander van der Burgt, The Royal Botanic Gardens Kew

Martin Cheek, The Royal Botanic Gardens Kew