Buhweju

A(i)Site contains one or more globally threatened species, B(iii)Site contains an exceptional number of socially, economically or culturally valuable species

Buhweju IPA contains 19% of the species found on the useful species checklist, well in excess of the 3% threshold and so triggering criteria B(iii). Additionally, the globally threatened perennial herb, Oenanthe mildbraedii (VU), occurs in Buhweju IPA, serving as the only IPA confirmed to contain this threatened species, making it one of the best sites nationally, and triggering criterion A(i)

Buhweju Important Plant Area (IPA) is located within the eastern portion of Buhweju district in the western region of Uganda. Nsiikais the largest town, located in the western part of the district. Lake George is situated 25 km to the northwest of the IPA, while the capital city of Kampala is approximately 323 km to the northeast. Kasyoha – Kitomi Central Forest Reserve (CFR), another IPA, is encompassed within the western portion of Buhweju district. The site is characterised by a mountainous and hilly terrain reaching 2,169 m asl, composed of both steep slopes and gentle curves. Steep escarpments outline much of the district border in the northeast, east and south, historically preventing the establishment of major accessible roads, making it a relatively isolated district (Doornkamp 1964).

Buhweju IPA is the single most species-rich site for useful plant species outside of a protected area within Uganda (O'Sullivan et al. in press 2024). Containing 202 useful plant species, it comprises 19% of the national checklist, triggering criterion B(iii) for designation as an IPA. This high level of plant richness may be attributed, in part, to its location, as Buhweju IPA sits at the edge of the western highlands and Lake Victoria Basin and consists of a varied landscape with fertile soils. However, this recorded abundance and diversity of useful plant species is also the result of a recent detailed and dedicated ethnobotanical study and collection effort. Most of the occurrence records from this site are less than 20 years old and are almost exclusively derived from the survey efforts of a single botanist, Protase Rwaburindore of Makerere University Herbarium. It is possible that other non-protected areas within Uganda may reach or even exceed this richness in useful species following similarly exhaustive surveys; however, Buhweju IPA represents the only such site for which significant examples of useful plant species are reflected by the empirical evidence of georeferenced occurrence records. It therefore highlights the major need for similar work to be undertaken in other localities within Uganda to see if they too qualify as IPAs under this criterion. Most importantly, it showcases the fact that even in a heavily populated area, that botanical richness of this level can nevertheless persist, and is intrinsically worthy of the designation of Important Plant Area.

The tree fern species Alsophila (Cyathea) dregei (LC) is one such useful plant species found in Buhweju IPA and is relatively rare within Uganda (Kalema & Hamilton 2020). The leaves and roots of this plant can be used medicinally for a variety of ailments from toothaches to parasite infections, to use during childbirth (Palmer-Newton 2018). The bark of A. dregei is also commonly sold as a growing substrate for epiphytic plants such as orchids. Additionally, the ‘trunk’ may be used variously for handicrafts, as it can be carved into figures or sliced to reveal the intricate internal patterns which make appealing plates (Masinga et al. 2018). This species is mostly documented from partly shaded to exposed areas within riparian habitats, open grasslands, or edges of forests. It may be sensitive to climate change, as it is strongly influenced by precipitation in the driest month as well as the annual mean temperature (Karichu et al. 2024). It is however strongly fire adapted. When fires are fast-moving, its fibrous trunk enables them to pass through without critical damage inflicted to the trunk.

Also found within Buhweju IPA is the globally threatened perennial herb, Oenanthe mildbraedii (VU). It is known to occur between 1600-2400 m asl in semi-aquatic environments such as wet grasslands swamps, edges of rivers and streams, and bogs (Ntore et al. 2019). Swamps at the bottom of valleys have been identified within Buhweju as areas which remain significantly intact (Rwaburindore 2002) which is encouraging for the status of this species within the district. Mining activities and erosion, however, may harm the health of this habitat (see ‘Conservation issues’). Therefore, follow-up surveying is recommended for this species within Buhweju IPA to promote its protection within the community.

Buhweju sits on a bedrock primarily composed of Precambrian schists, slates, quartzites, phyllites, amphibolites, and gneisses as well as Pleistocene tuffs and agglomerates (Bahiru & Woldai 2016) of Karagwe-Ankolean/Kibaran rocks (Kaggwa et al. 2024), see also ‘Conservation issues.’ Throughout Buhweju IPA, most soils are iron-rich ferrallitic loamy and volcanic, with varying proportions of sand and clay (Buhweju District Local Government 2020).

Rainfall in the district is high, between 1,000-1,500 mm per year, with an annual mean of about 1,072 mm (Bright Technical Services 2022). A bimodal pattern of precipitation takes place in Buhweju, with the wettest months being March-May with the peak in April and September-November with the peak in October. January and July being the driest. The mean temperature is 25ºC, with the warmest month being February, reaching 27ºC, and the coldest month being December, with a minimum temperature of 16ºC (Rwaburindore 2000).

Much of Buhweju IPA’s landscape is dedicated to farms and households with minimal tree cover comprised of Eucalyptus species around administrative centres, such as District Headquarters and Sub-County Headquarters. Around individual landholdings, species of pine are the most common. The non-cultivated areas within greater Buhweju are made up of Forest/Savanna Mosaic dominated by Phoenix reclinata, Acacia polycantha and grass layer of mostly Cenchrus purpureus, Hyparrhenia rufa and Imperata cylindrica mixed with post-cultivation communities of Hyparrhenia cymbaria, H. diplandra, and Cenchrus unisetus grasses, along with Pteridium aquilinum (Langdale-Brown 1964). Numerous rivers and streams cut through the hilly slopes, with Papyrus swamp habitat persisting in the valley basins. The common species in wetlands are Cyprus papyrus, C. latifolia, Miscanthidium violaceum, and Vossia cuspidata. Within Karungu sub-county can be found a waterlogged forest just below the former Isingiro Forest. This relatively intact, non-gazetted area 1400 – 1500 m asl has not been well explored for its composition of plants. Further surveys are recommended to better understand the habitat structure, as well as presence of useful and possibly threatened plant species (Rwaburindore, pers. comms 2024).

Waterfalls can be seen flowing over the exposed rock and rippling hills in Kyenjogyera parish, Buhunga sub-county, where the source of river Rwizi is found. The Rwizi is the longest and largest river in western Uganda, which eventually feeds into Lake Victoria (Matsiko 2022).

The Buhweju IPA is not formally protected. Between 2002 and 2023, 251 ha of humid primary forest were lost in the district broadly (REFS). The greatest losses took place from 2019-2020, when almost 200 ha were removed. Since then, rates of loss have dropped significantly, with less than 1 ha lost per year since 2022. Less than 120 ha of forests remain in the entirety Buhweju district, excluding that of Kasyoha-Kitomi CFR (Global Forest Watch 2024). Reforestation efforts have taken place in collaboration with external organisations and universities, planting several thousand indigenous trees within the district (von Gaudecker 2023).

Recently, encroachment into wetland areas has been steadily increasing through the establishment of homes and agricultural settlements as the population increases in the district. This has led to soil erosion along the riverbanks, increased sedimentation within the wetlands, and loss of healthy riparian habitat. However, local officials and environmental action groups are working to raise awareness and offer alternative income sources in order to protect these wetlands especially that of the Rwizi water catchment, which is encompassed in the Buhweju IPA (Matsiko 2022).

Because of its unique geology, Buhweju is rich in numerous minerals such as gold, lime, and others, which are actively mined and quarried (Rwaburindore 2000, Bahiru & Woldai 2016). Artisanal gold mining practices have also been found to impact the health of Buhweju’s wetlands, particularly in Bitsya sub-county, where many useful plant species have been documented. A gradual decline in vegetation health has been observed where gold mining has occurred in Bitsya, particularly, in the inner-most portions of the wetland. This could possibly be due to the use of mercury when separating gold from sand, as well as a lack of effort to fill-in and revegetate mined areas (Nuwagira, 2023).

Climate change has significantly impacted agricultural production and livelihoods in Buhweju. For example, tea production in 2022 was reduced by almost half. This loss in harvest has been in part attributed to the increasingly unreliable rainfall patterns, droughts, and landslides. Additionally, bush burning and logging on the hills are leading to increased erosion, worsening the impacts of the changing climate patterns (Amanyisa 2022).

Many people throughout Buhweju district are smallholder farmers producing staple crops like bananas and finger millet, and other pastoral farmers graze cattle, sheep and goats along the hillsides. Cash crops like coffee and tea are grown in smaller amounts (Buhweju District Local Government, 2024). The few and poorly maintained roads have historically limited residents’ access to larger cities where they may be able to make a larger profit on their goods, and access schools and clean water, contributing to the relative impoverishment of the local community. This has likely reinforced the community’s dependence on their land for resources, and where left unregulated, has resulted in encroachment on sensitive habitats, such as wetlands (Doornkamp 1964, Matsiko 2022). Recent initiatives for ecotourism and cultural programs within the district have been developed to help diversify the incomes of people in Buhweju, and to support municipal projects such as road improvement (Rwaburindore 2000, Centre for Integrated Community Development Uganda 2023). Identification of a portion of Buhweju as an IPA is intended to strongly support these on-the-ground initiatives aimed at improving livelihoods.

Buhweju IPA provides direct provisioning access to useful plant species, ranging from foods and medicines, to charcoal, fibres, timber, and grazing fodder. Community members can also access plants which are socially and spiritually important. The abundance and diversity of these plant species can help to promote ecotourism and natural resource projects within the community, and therefore supports community livelihoods.

Natural areas within Buhweju IPA provide access to local people for cultural activities, as well as attracting ecotourism. The Mukazi Anyara River is one such culturally important site, as it is believed that the water has healing properties. Residents of the community historically utilise it for ceremonies and rituals along the riverbanks. It also draws the interest of spiritual visitors seeking healing, as well as recreationists looking to enjoy the waterfalls, birdwatching, fishing, or kayaking (Allens Ladu, 2023).

Assessed by:

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: 26th Nov 2024

Reviewed by:

Protase Rwaburindore, Makerere University Herbarium