Western Area

A(i)Site contains one or more globally threatened species, C(i)Site contains globally threatened or restricted habitat or vegetation types

This site qualifies as an IPA as it contains 35 threatened species that trigger A(i), as well as two endemics that trigger A(iii). This site contains a significant number of species of high conservation importance, thus triggering criterion B(ii).

The Western Area IPA is situated on the Freetown Peninsula in the Western Area Rural District of Sierra Leone. This forested mountainous peninsula lies adjacent to the capital city, Freetown, and forms part of the landscape originally referred to as “Serra Lyoa” or “Lion Mountain” by the Portuguese, a name that later gave rise to the country's name, Sierra Leone.
This IPA largely overlaps with the Western Area National Park, a protected area encompassing the westernmost remnant of the Upper Guinean forest. The IPA also includes the Tacugama Chimpanzee Sanctuary, as well as the Guma Valley and Congo Dam reservoirs.

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This site is an important reserve of the Guinean Forests of West Africa Biodiversity Hotspot. It contains many species endemic to these forests, and is an important refuge for many threatened plants across this region. Such examples include the understory trees Aulacocalyx divergens (VU), Pavetta leonensis (EN), Pleioceras afzelii (EN); large trees such as Brachystegia leonensis (VU) and Tessmannia baikiaeoides (VU); as well as the liana Dalbergia hepperi (EN).
Of particular botanical significance is Bulbophyllum parvum, an epiphytic orchid known only from the Western Area and documented from a single collection in 1951 (Jones #235). While sterile Bulbophyllum spp. were observed at suitable habitat during recent fieldwork in February 2025, follow-up surveys during the wet season flowering window (October/November) are required to confirm its persistence. This orchid is assessed as Data Deficient (in draft), highlighting the urgent need for further study of this narrow-range endemic. The site's inselberg habitats support additional national endemics including Dryopteris amblyodonta (EN in draft) and Loudetia jaegeriana (NE), along with the near-endemic rare grass Anadelphia trichaeta (VU). The bowal habitat at this IPA is also crucial for the conservation of the rare herb Eriocaulon adamesii (CR), containing most of its known distribution (Mesterházy 2020). This is a large site and has not exhaustively botanically explored, therefore likely that additional species of conservation concern remain to be recorded within this IPA.

The Western Area IPA is characterised by closed evergreen and semi-deciduous forests forming part of the West African forest ecosystem, however the area comprises a mosaic of habitat types. Extensive areas of moist evergreen and semi-deciduous forests cloak the slopes and valleys, but forest has almost entirely been cleared from the flats. Additionally, rocky river species feature along drainage lines. At lower elevations, mangrove swamps fringe estuaries, dominated by Rhizophora spp. and Avicennia spp. Scattered throughout the hills are inselbergs—steep, isolated rock outcrops, at 400 – 850 m altitude, with small patches of vegetation occurring in cracks in the rock. Dominant species may include Ficus spp., Eremomastax speciosa, Dracaena spp., Vepris spp., Psorospermum sp., and various grasses. Bowal habitat is scattered along the coastline, and these areas are characterised by shallow, ferraltic pans that support sparse grassland vegetation (A. Lebbie pers. comms. 2024). These areas may be easily mistaken for cleared areas, however, they support a unique assemblage of species of conservation importance.
Geologically, the peninsula is underlain by the Freetown Complex, a mesozoic mafic intrusion associated with the continental rifting and opening of the Atlantic Ocean (Goodenough et al. 2018). This gives rise to rugged topography at the site, with steep, forested slopes descending directly into the Atlantic Ocean. Recent Bullom Group marine and estuarine sediments occur along coastal margins (Goodenough et al. 2018).

The site experiences significant threats from unsustainable human activities including illegal farming, logging, wood-cutting, sand and stone extraction, unplanned urbanization, land grabbing, poor waste management, mining, and hunting; all exacerbated by rapid population growth in Freetown and associated infrastructure expansion (Okoni-Williams et al. 2001). These pressures are compounded by enforcement challenges, as National Protected Area Authority (NPAA) forest guards lack adequate resources to effectively patrol and protect the reserve boundaries, while changing administrative boundaries create additional management complications. Fire represents a persistent threat that alters vegetation composition and degrades habitat quality for sensitive species. Climate change impacts, particularly increased frequency and severity of coastal erosion, flooding, and storm surges, severely affect the coastal areas around the park. The establishment of new settlements along park borders has intensified encroachment pressures (Okoni-Williams et al. 2001), while the dense human population of Freetown continues to drive illegal resource extraction activities. Bowal habitats are under development pressure also, with patch of bowal habitat currently being developed into a new campus for the University of Sierra Leone (A. Lebbie pers. comm. 2024). These combined pressures have resulted in alarming deforestation rates and habitat loss for many threatened species, highlighting the urgent need for integrated conservation action and sustainable development approaches.

The Western Area IPA provides critical ecosystem services, especially to the capital city Freetown. Most significantly, the forested slopes protect the headwaters of the Guma Valley and Congo Dam reservoirs, which together supply approximately 90% of the city’s drinking water (World Bank 2020). These forests play a vital role in intercepting rainfall, reducing surface runoff, promoting infiltration, and maintaining dry season baseflow (Hackman 2017). Vegetation also provides essential slope stabilisation across the region’s steep terrain, helping to prevent landslides and soil erosion. The devastating 2017 Regent landslide, which killed over 1,000 people, occurred adjacent to the Western Area National Park and was strongly linked to deforestation and unregulated urban expansion (Haile et al., 2019). Scientific assessments following the disaster have confirmed that intact forest cover significantly increases slope stability by binding soil and reducing saturation during extreme rainfall events (Hackman, 2017; Haile et al., 2019). In addition, the Western Area is an ecotourism hotspot, due to the presence of the Tacugama Chimpanzee Sanctuary, which is currently building a botanic gardens at the site.

Gabriella Hoban, Royal Botanic Gardens, Kew

Xander van der Burgt, Royal Botanic Gardens, Kew

Aiah Lebbie, The University of Sierra Leone

Momoh Plato Sesay, The National Herbarium of Sierra Leone

Samuel Sokpo, Njala University

Fanny Massally, Royal Botanic Gardens, Kew

Date of first assessment: 1st Aug 2024

Date of latest reassessment: 1st May 2025