Mount Elgon

A(i)Site contains one or more globally threatened species, A(iii)Site contains one or more highly restricted endemic species that are potentially threatened, B(ii)Site contains an exceptional number of species of high conservation importance, B(iii)Site contains an exceptional number of socially, economically or culturally valuable species, C(iii)Site contains nationally threatened or restricted habitat or vegetation types, AND/OR habitats that have severely declined in extent nationally

Mount Elgon qualifies as an IPA under criterion A(i) as it contains globally important populations of 29 threatened taxa, of which three are Critically Endangered and 12 are Endangered and 15 are vulnerable. The presence of the endemic, Data Deficient species Silene syngei also triggers sub-criterion A(iii). Mount Elgon also qualifies under criterion B(ii) as it supports populations of 2929 of the priority taxa on the agreed national list, well in excess of the 3% threshold for that sub-criterion. Mount Elgon additionally qualifies under B(iii) is also in excess of thethe 3% threshold of taxa found on the national list of useful plant species.

Mount Elgon Important Plant Area (IPA) is located on the Ugandan side of Mt. Elgon. This mountain is an ancient inactive volcano (ACCESS 2015), spanning the border of Uganda and Kenya. Formed in the Miocene epoch, it is estimated to be approximately 24 million years old (UWA 2000). It spans 50 km from east to west, and 80 km north to south (Muhweezi et al. 2007) and covers over 1,279 km2. This makes Mt Elgon both the oldest and largest solitary volcanic mountain in eastern Africa, with the largest known mountain base in the world. At the top is a vast crater, or caldera, approximately 8 km in diameter, making it the largest intact caldera globally. Mount Elgon has 5 major peaks, with the highest peak, Wagagai at 4,321 m, found on the Ugandan side. Currently, it is the fourth tallest mountain in East Africa, and eighth in Africa (Rono et al. 2023; Howard 1991).

On the Ugandan side, the mountain is found 235 km north-east of Kampala and 8.5 km east of the town of Mbale. Mt Elgon borders the eight districts of Bukwo, Kween, Kapchorwa, Bulambuli, Sironko, Mbale, Bududa and Namisindwa. It is contained within Mt Elgon National Park (MENP), spanning 1,121 km2, and comprising 28% of the mountain’s extent.

Mount Elgon is a globally important site for plant and animal biodiversity, and as such is a designated UNESCO World Heritage site. The geographical isolation and large size of Mt Elgon have led to a diversity of plants found throughout the many vegetation zones on the mountain. Floristically, Mt Elgon is primarily constituted by the Afromontane archipelago-like centre of endemism (White 1983). Some of the southernmost parts of the mountain also contribute to part of the Lake Victoria regional mosaic, which extends through Uganda to Rwanda, Burundi, and parts of Congo and Tanzania (Rono et al. 2023). Its flora dates back 22 million years, as it is one of the oldest East African floristic regions. Numerous species found throughout East Africa are thought to have diversified here, spreading through the rest of the region (Rono et al. 2023; UWA 2022).

As of 2024, 1,709 plant species have been documented across Mt Elgon, covering both the Ugandan and Kenyan portions. Of those, 103 have been identified as endemic, and at least 14 species are both endemic and rare (Rono et al. 2023). Several of these strict Ugandan-endemic species are only found on the Ugandan side of the mountain. These include the critically endangered (CR) species Arabis elgonensis found in moorland and alpine areas and Bothriocline auriculata from montane forest and bamboo. Snowdenia microcarpha (CR) is only known from margins of moist forests, documented from just outside the reserve boundary – and only known from type specimens. Located within the moorland are Erucastrum elgonense (VU) and Rubus friesiorum subsp. elgonensis (LC). Aloe wanalensis, currently listed as LC, is endemic to rock outcrops in the western arm of MENP as well as just outside the park's boundary, maintaining a level of protection from its inaccessibility (Cole & Forrest 2017). Additionally, Silene syngei (DD) has been found on rock faces in moorland but requires further surveying to understand its extent on the mountain (Rono et al. 2023, Kalema et al. 2025).

Several other species that are found only on Mt. Elgon have been found on both the Ugandan and Kenyan sides of the mountain and are therefore near-endemic to Uganda. These near-endemic species include some assessed as Vulnerable such as Erica trimera subsp. elgonensis (VU), Euryops elgonensis (VU), Imptiens miniata (VU), Luzula mannii subsp. gracilis (VU), and Swertia uniflora (EN) . Other species endemic to Mt. Elgon that are on both the Ugandan and Kenyan sides have been assessed as Least Concern, usually due to populations in inaccessible places, and/or possessing adaptations such as those that enable them to survive increasingly drought and fire-prone environments. These include Dendrosenecio elgonensis (LC), Helichrysum amblyphyllum (LC), Impatiens digitata subsp. phlyctidoceras (LC), Impatiens tweedieae (LC), Ranunculus crypanthus (LC), Senecio snowdenii (LC), and S. sotikensis (LC). However, should the impact of climate change and the frequency or intensity of fires continue to increase, these species may become imperiled. Continued monitoring of these species is therefore required to understand how their populations will respond to these threats.

Within Uganda, Tarenna pavettoides subsp. friesiorum (VU ) has only been documented on Mt Elgon, though it is found also in Kenya within Fourteen Falls, Embu, and Mount Kenya, as well as the South Pare Mountains in Tanzania. Similarly, Psychotria fractinervata (VU) is only known from seven locations across Uganda, Kenya and Tanzania – with Mt. Elgon being the only Ugandan location. Some species, like Alchemilla elgonensis (VU), and Bidens elgonensis (VU) are also shared with the Cherangani Hills in the western highlands of Kenya. Ensuring the protection of vulnerable species within Uganda that span these East African borders will help to promote species’ genetic diversity, especially in the face of threats to habitat and climate.

Alongside threatened species, this IPA is one of the most important sites for the nationally endangered habitat, Afromontane rainforest, hosting 35% of the national resource (REF). Significant areas of this forest have already been lost on Mt Elgon, particularly on the more sheltered southwestern slopes where this habitat is thought to have extended to lower altitudes than at present (Langdale-Brown et al. 1964; van Breugel et al. 2015). On the drier northern slopes of this mountain, the forest transitions to Afromontane dry forest [Afromontane undifferentiated forest] and is dominated by Juniperus procera and Afrocarpus (Podocarpus) gracilior. Although there is only a small extent of this habitat within this IPA (48 km2), Afromontane undifferentiated forest is rare nationally and so it is estimated that around 20% of the national resource lies within MENP (Richards et al. 2024). Therefore, this habitat type also triggers criterion C(iii) under the IPA criteria.

Mt Elgon contains 143 useful native or naturalised plants and so exceeds the criterion B(iii) threshold. Many of these socially, culturally, and economically important species are greatly relied upon by the populations which live around MENP (See ‘Key Ecosystem Services’). Further, there are at least eight crop wild relatives found here, including the grass species Eleusine jaegeri, and legume species Vigna friesiorum, both of which are also utilised for food. A collection of almost 200 ethnobotanical vouchers can be found in Makerere University Herbarium, collected by Norgrove during fieldwork in 1999, and Jewsbury in 2000 (Norgrove 2003).

Mount Elgon is situated on the Trans Nzoia Plateau, a flat, low-relief region formed from the Precambrian Basement Complex and shaped predominantly by stream erosion. The mountain is primarily composed of coarse igneous rocks with minimal quartz or feldspar content, punctuated by basaltic lava outcrops. The broader geological structure includes undifferentiated volcanic rocks, with alkaline intrusives in some areas, overlaying Precambrian granitoid batholiths, gneisses, schists, and granulites at the lower slopes (ACCESS 2015). According to Synnot (1968), the soils on Mt. Elgon are relatively young, erosion-resistant, and rich in weatherable minerals, particularly from the Andisol series in Uganda. Mt Elgon is characterized by steep cliff edges separated by gently sloping shelves, with streams flowing down its slopes. It also features a 20 km-long ridge called the Nkokonjeru Peninsula, extending west toward the town of Mbale.

Due to the location and unique topography of Mt Elgon, the Ugandan and Kenyan sides vary in climate and ecology. While increasing elevation on the mountain correlates with higher average rainfall, precipitation is generally greater on the Ugandan southern and western slopes than on the northern and eastern slopes within Kenya. There is a bimodal pattern of precipitation, with rain from March to May, and again between September to November. This is interspersed with dry seasons in June to August, and again from December to March. Annual levels of rainfall vary from 1,400-2,500 mm, contributing greatly to agricultural production in the region. Locations between 2,000-3,000 m asl along the western and southern mid-slopes of Mt Elgon receive the highest levels of precipitation due to south-westerly winds from Lake Victoria (Vedeld et al. 2016; UWA 2022).

Within Mt Elgon there are several distinct zones of vegetation. The lower reaches of the MENP, between 1,520 m and 2,930 m, are comprised primarily of Afromontane rainforest. This habitat type can also be seen extending onto Nokononjeru peninsula. Here, the habitat is characterised by the tallest trees being scattered Prunus africana (VU), with instances of Aningeria adolfi-friederici, Markhamia platycalyx, and Ficus spp. There is a shrub layer of Macaranga kilimandscharica, and climbers stretching up out of an understorey of scramblers. The tree fern Alsophila deckenii can be found growing alongside streams in this vegetation zone. In the northeast of MENP near the Kenyan border, this habitat transitions into Juniperus-Podocarpus Dry Afromontane Forest characterised by Juniperus procera, Podocarpus milanjianus, Afrocarpus gracilior and Acacia (Vachellia) abyssinica. Additionally, two small examples of Acacia-Cymbopogon/Themeda Complex (totalling 3.83 km2), adjacent to Kabei and Senendet sub-counties can be found at the lowest elevations of the park.

This is followed at higher elevations by a belt of Hagenia-Myrsine (Rapanea) Moist Montane Forest and Oldeania (Arundinaria) Montane Bamboo Forest along the southwest and northeast portion of Mt Elgon, extending to 3,230 m and 3,150 m respectively. There is a distinct break in this habitat zone between the streams Sipi and Chebonet to the Bukwa, comprising Hagenia-Myrsine Moist Montane Forest, which sits between 2,620 and 3,210 m. Here, Hagenia abyssinica is dominant along the flatter edges of the slopes, with Myrsine melanophloeos found on the steeper inclines, and Erica mannii along the highest reaches. Prunus africana can also still be found, but in much lower abundance.

From 2,890 m to 3,840 m can be found the Ericaceae-Seriphium (Stoebe) Heath zone. On Mt Elgon, this vegetation consists of true heathers or Erica spp. like Erica trimera, as well as Seriphium kilimandscharicum (Stoebe kilimandscharica), a species of Compositae with a heath-like habit, plus small shrubs, herbs and graminoids such as Hypericum revolutum subsp. keniense and Carex runssoroensis. Arborescent rosette forming Lobelia stuhlmannii, L. bequaertii and Dendrosenecio erici-rosenii are also notable in this habitat, along with climbers like Galium ruwenzoriense. In some parts of the mountain, these heathlands have been transformed into open grassy fields due to burning and grazing (Langdale-Brown et al. 1965).

Within the caldera of Mt Elgon, beginning at 3,380 m is an Alchemilla-Helichrysum Moorland with the dominant vegetation being Alchemilla elgonensis (VU), Helichrysum amblyphyllum, and Arabidopsis thaliana. Species of arborescent Lobelia and Senecio can also be found here, like the Mount Elgon endemic and Ugandan near-endemic species Dendrosenecio elgonensis subsp. barbatipes, especially near to the crater rim in drier areas, as well as Lobelia gregoriana subsp. elgonensis (CR). Within the more boggy habitats can be found an abundance of Carex runssoroensis (LC), often growing on exposed rocks. (Langdale-Brown et al. 1964; Hamilton and Perrott 1981; Plumptre et al. 2021).

Between 1924 and 1993, the Forest Department managed Mt Elgon in Uganda. Historically, the mountain was home to many people, including the Benet who lived in the high-altitude moorland ecosystem. It was designated as a Crown Forest in 1938, and then became a Forest Reserve in 1951, with the dual purpose of protecting the forest and extracting timber (Synott, 1968). The 1975 Land Reform Decree led to a shift in land management by ostensibly opening reserve land to the public, resulting in unclear and insecure access to land for rural communities. During this period, forest governance weakened, and legitimate licensing for land use deteriorated, leading to increased grazing and agriculture on the mountain slopes and into forested areas. Consequently, between the 1970s and 1980s, nearly 25,000 hectares of the reserve land were deforested (Webster & Osmaston 2003; Cavanagh 2015). In response to these pressures, a 1983 parliamentary measure enacted the resettlement of people outside the boundary of the forest. Further to this, the Ugandan side of Mt Elgon was designated a national park in 1993, managed by the then Uganda National Parks (now Uganda Wildlife Authority). The implementation of national park status aimed to address the escalating exploitation of natural resources by enhancing protection measures. Today, the national park’s use is restricted to activities related to biodiversity conservation, scientific research, recreation, scenic viewing, and other legally approved economic activities (GoU 1996). As of 2003, it is a designated UNESCO Biosphere Reserve (https://www.unesco.org/en/mab/mount-elgon-0) and has also been classified as a Key Biodiversity Area due to both its cultural importance as well as its biological diversity (Plumptre et al. 2019).

MENP is presently divided into six zones, of which various activities are permitted or prohibited. These include plantation zone, administrative zone, tourism zone, collaborative resource management zone, restoration zone, and wilderness zone. The wilderness zone, comprising 40% of MENP makes up by far the largest proportion of the park.

On the outskirts of MENP are two large populations of Bagisu people in Mbale and Sironko Districts, as well as the Sabiny in Kapchorwa. Just upland from the Sabiny also live the Benet, who still also occupy internal portions of MENP. Together, these make up one of the most densely populated areas in the country. These communities rely mainly on intensive small-holder agricultural production of Irish potatoes and maize in Kapchorwa. Matooke (Musa spp.) and maize are farmed for sustenance and as cash crops in Mbale and Sironko, augmented by enterprise in passion fruit, onions and coffee production, along with market trading. The Sabiny also rely on livestock for subsistence and as work animals, especially donkeys. These populations rely heavily on the land outside Mt Elgon, and historically have utilised resources found within the MENP border (see Key Ecosystem Services). This has led to both historical and modern pressures to cultivate the lower sections of the national park, with encroachment visible along much of the park’s border, into the most threatened, forested habitats found within the park (Norgrove & Hulme 2006).

Where deforestation and agricultural transformation have occurred on Mt Elgon, particularly on the steep, north-facing, concave slopes of the mountain, landslides have occurred. This poses a major threat to the populations surrounding the mountain, as lives can be quickly imperilled by shifting ground, as well as drastically reshaping the mountain’s ecosystems. Increased stream sedimentation, fires, and habitat loss can all result from these devastating events (Mugagga et al. 2012; Discover 2022). To this end, restoration zones have been delineated in areas that have experienced severe degradation due to encroachment and resource depletion, namely a zone in the north, south of Binyin, and one on the west of the mountain, adjacent to Bugitimwa.

Significant community-based restoration activity has also occurred along the southwestern bend of MENP, just below the Nkokonjeru Peninsula, in the sub-counties of Bukinga, Bulucheke, Bukalasi, and Bududa. Within this region of MENP, a memorandum of understanding has been established to conduct taungya restoration through joint native tree planting and crop farming below restored trees throughout 767 ha of land within the national park, while allocating another combined 3294 ha in this area where resource extraction activities are limited. Subsistence and cash crops in the Taungya zone that have been planted here include maize, beans, onions, carrots, and cabbage. Above these crops are planted tree species including Albizia coriaria, Bridelia micrantha, Croton macrostachyus, Khaya anthotheca, Olea welwitschii, Afrocarpus gracilior, Prunus africana and Spathodea campanulata (Kamukasa Adonia 2015).

Mount Elgon is also home to an array of amphibian, reptile, bird and mammal species; several of which are also endemic and/or threatened. Combined with its diversity of plant species, MENP is also both an Important Bird Area (IBA) and a Key Biodiversity Area (KBA). The globally endangered Barbours Vlei Rat (Otomys barbouri) is only found in Mt Elgon’s high-altitude grassland mosaics and moorlands (Kennerley & Taylor, 2017; Key Biodiversity Areas Partnership 2024). Additionally, the Elgon Francolin (Scleroptila elgonensis) (NT) is restricted to Mt Elgon; it too relies on the high-altitude grasslands and moorlands, and has been documented feeding on plant roots and bulbs in these habitats (Del Hoyo et al. 1992; BirdLife International 2016). Likewise, the Mountain Buzzard (Buteo oreophilus) (NT) is also found in high-altitude forests and grasslands within Mt Elgon (BirdLife International 2022; Del Hoyo et al. 1992). The Mt Elgon Forest Gecko (Cnemaspis elgonensis) (VU) has been documented in a few fragmented populations in the montane forests and clearings throughout the mountain. While it has also been documented in the Ruwenzori Mountains, another IPA, it is only known from a single record in Rwenzori, requiring further surveying to assess whether this population is still viable (Wagner et al. 2022).

This diversity of plant and animal species is, however, threatened by invasive species which have been documented on Mt Elgon. Records of invasive plant species like Lantana camara are found on Mt Elgon, which is considered one of the most problematic invasive non-native alien species in the region (Rono et al. 2024). The invasive longhorn crazy ant, Paratrechina longicornis, was identified as recently as 2014, near the origin of Sasa trail, Budadiri (Vanderhaegen et al. 2019). Accidental introductions of invasive species within parks are commonly caused by people, as plant seeds, insect eggs, and pathogens can cling to footwear. The location of these primary instances of crazy ant suggests introduction through visitors and highlights the need for increased biosecurity measures taken at the park, like boot cleaning stations and signage educating visitors on these detrimental species. Such invasive species can impact the biodiversity of Mt Elgon by outcompeting other ant and insect species, as well as by encouraging other pests like scale insects, which can harm both native plants as well as crops grown just beyond the park border.

Mt Elgon provides numerous essential ecosystem services, most notably supplying water to millions of people in Uganda. Located 140 km northeast of Lake Victoria and ca. 85 km east of Lake Nakuwa, Mt Elgon serves as a catchment for both lakes, as well as Lake Turkana and the Nile River through the mountain’s network of rivers and tributaries.

Traditionally, local people have made use of numerous edible plants and fungi, such as Garcinia buchananii and Armillaria mellea, as well as medicinal plants like Erythrina abyssinica and Prunus africana (VU) to treat ailments like yellow fever. Edible bamboo (Oldeania alpina) is preserved (smoked) and consumed by the Bagisu as a delicacy called Malewa, and is central to many of their major ceremonies. Additionally, selling dried bamboo shoots is an important source of income for Bagisu households (Norgrove, 2002). However, access to this key resource is a major driver of continued friction between local people and park managers (Collins Bulafu, pers. comms.)

Many plants are also culturally and ecologically important to the indigenous people around Mt Elgon, with access to them enabling the practice of important ceremonies and rites of passage. They also rely on forest resources for fuel, fibres, and timber for both domestic use and to supplement income (Norgrove 2003; Norgrove & Hulme 2006). Additionally, the fertile volcanic land is ideal for cultivation and grazing and has in the past played a significant role in supporting rural livelihoods. Animal hunting historically provided additional subsistence of meat to the surrounding communities, along with the use of animal pelts like that of the black-and-white colobus monkeys (LC) for ceremonies (Shikuku et al. 2018). However, access to these resources is subject to MENP agreement, with activities such as hunting, grazing, and cultivation being prohibited (GoU 1996). A 1 km wide collaborative access zone around the park has been permitted for communities to access agreed-upon resources like edible and medicinal plants and fungi, wild honey, and firewood for domestic use. Further, there are currently about 70 agreements designating the use of resources by local people within MENP (UWA 2022).

The scenic quality and scale of Mt Elgon make it an ideal tourist destination in Uganda, which the UWA has highlighted through the Tourism Policy of Uganda (2013) as a means of reducing poverty through nature-based tourism. This includes access to accommodation, provision of cultural education, and voluntourism (Cavanagh 2015). This takes place primarily in the tourism zone, along six delineated trails of the mountain, and within the caldera. Tourism also benefits the surrounding communities through revenue-sharing schemes, aimed at improving livelihoods. Many areas of Mt Elgon also hold cultural and spiritual significance, serving as sites for religious ceremonies. Access to these sites provides continued enjoyment of many longstanding cultures and traditions, as well as visitation and use of burial sites.

As the site contains numerous threatened indigenous species and several CWRs (see Botanical significance), it serves as an important refuge to these plants which may be of value in future research, for instance, in developing pest and disease-resistant crop varieties. Seed collection programmes run by local individuals, in collaboration with organisations such as the Mt Elgon Tree Growing Enterprise, work with nurseries and local NGOs to collect and store a variety of native and useful plant species. They serve as suppliers of local seeds for reforestation efforts and contribute to long-term seed-banking (Discover 2022).

Haley Gladitsch, Royal Botanic Gardens, Kew

Iain Darbyshire, Royal Botanic Gardens, Kew

James Kalema, Makerere University Herbarium

Samuel Ojelel, Makerere University Herbarium

Florence O'Sullivan, Royal Botanic Gardens, Kew

Date of first assessment: 15th Jan 2025

Colins Bulafu, Makerere University