Ssese Islands

A(i)Site contains one or more globally threatened species, B(ii)Site contains an exceptional number of species of high conservation importance

Ssese Islands qualify as an IPA under criterion A(i) as they support globally important populations of the Endangered Sabicea entebbensis, Uvariodendron fuscum var. magnificum and Polystachya eurygnatha, as well as the globally Vulnerable Faroa graveolens and Tricalysia bagshawei S.Moore subsp. bagshawei. It also qualifies under criterion B(ii) as it is among the top 13 richest sites for endemic taxa.

The Ssese Islands IPA is made up of forested parts of Bugala Island, which is the largest (at ca. 200 km²) of the 84 islands in the Ssese island Archipelago of Lake Victoria (BirdLife International 2024), together with Bufumira Island (ca.14 km2) which is to the east of Bugala, Mazinga Island (ca.12 km2) to the south east of Bugala, parts of Nkusa Island (ca. 1.6 km2), Mpugwe Island (ca. 1.4 km2) to the south east of Bufumira and Kalambide Island (ca. 0.2 km2). This IPA is situated ca.35 km east of Masaka Town, within Kalangala district, in the U4 floristic region in the central part of Uganda (Buganda). There are 31 Central Forest Reserves in the Ssese Islands, covering a total area of 8.861 ha (NFA 2008).

The primary activities in the Ssese Island IPA are fishing, forestry, and agriculture, mainly growing crops such as maize, coffee, beans, millet, sweet potatoes and banana as well as livestock keeping (Uganda Bureau of Statistics, 2017). An estimated 1,300 smallholder farms, consisting of a mix of subsistence and landless farm families, were scattered across the island at the time of the establishment of oil palm plantations (IFAD 2011).

Ssese Islands IPA is important for the conservation of Uganda’s vegetation and flora. The areas of intact Medium Altitude Evergreen Moist Forest, a nationally Vulnerable habitat, are of particular importance, and this is a habitat that has been lost from much of the Lake Victoria region. The surveys conducted in the three forest reserves on Bugala (Busowe, Towa and Mugoye CFRs) revealed 148 species of Uganda’s known tree and shrub species (Lwanga 1996). Further botanical surveys by Kalema (2005) on vascular plants yielded 184 species while Ssegawa and Nkuutu (2006) recorded 179 species. The Ssese islands, in general, contain over 12% of Uganda’s known tree and shrub species.

This IPA is significant for the conservation of Uvariodendron fuscum var. magnificum (Syn: Uvariodendron magnificum), a tree species only known from Lutoboka forest on Bugala Island and Kasyoha-Kitomi CFR (Kalema & Beentje 2012, Kalema & Hamilton 2020). It is currently assessed as globally Endangered (IUCN SSC East African Plants Red List Authority 2013). Also known from Bugala is Sabicea entebbensis, a range-restricted climber in the forest edges and thickets, which is endemic to Uganda and is Endangered (Gereau et al. 2019). Polystachya eurygnatha is a globally Endangered forest obligate epiphytic orchid known to occur on Bufumira Island (Gereau et al. 2019).

Faroa graveolens, a perennial herb which grows in grassland and woodland (Amani et al. 2022) and Tricalysia bagshawei subsp. bagshawei, a shrub or small tree which grows in forest, evergreen thickets, and secondary growth (Amani et al. 2022) are globally Vulnerable species, both known from this IPA. Lasianthus batangensis (Syn: Lasianthus seseensis), a small shrub which grows in moist forest, is also known from the Ssese Islands IPA, and is globally Near Threatened (Ntore et al. 2019). This species is also known to occur in Tanzania, Rwanda and Democratic Republic of the Congo. Oldenlandia lancifolia var. seseënsis is a near-endemic herb with an EOO estimated at 6,898 km2, with the majority of this range being in Uganda. It is a perennial or rarely annual herb which grows in almost bare sand by lakeshores, cultivated ground and pathsides, and is currently assessed as LC (Gereau et al. 2019). Polystachya albescens subsp. musozensis, an epiphytic orchid with a narrow range of distribution in Burundi, DRC, Rwanda and Uganda (POWO 2024) is also recorded from Bugala. In Uganda, Dryopteris squamiseta, a perennial fern which grows primarily in wet tropical environments, is only known from Kalangala on Bugala Island (Kalema 2005). This is one of several apparently rare ferns from this IPA, including two potentially undescribed species: Blotiella sp. A of FTEA, and Diplazium sp. A of FTEA, both of which may be Ugandan endemics (Verdcourt 1999, Beentje 2008).

Two nationally threatened taxa are also noteworthy, though both are globally of Least Concern: Casearia barteri is a nationally Vulnerable tree species whilst Lagarosiphon ilicifolius, a submerged herb which grows in still or slow-flowing water, is nationally Endangered (Ministry of Tourism Wildlife and Antiquities 2018). Further surveys may reveal rarer and threatened plant species and other islands may be incorporated into this IPA in future.

The vegetation of Ssese Islands IPA is a mosaic of Themeda-Loudetia grass savanna, shrubland and medium altitude moist evergreen forest dominated by Piptadeniastrum and Uapaca (Langdale-Brown et al. 1964). Swamps of Cyperus papyrus are found in the low-lying inlets on the shores of Lake Victoria (Davenport et al. 1996). There are also evergreen thickets and secondary growth.

The topography of the islands has a gently undulating terrain (Ssegawa and Nkuutu 2006) which resulted from long-term land-forming processes. The soils are mainly ferralitic, sandy, clay and loamy (Kalangala District Local Government 2005). The soil of the forest areas is different from any seen elsewhere on the Ssese Islands - it is a heavy brown loam, over a subsoil of yellow clay (Thomas 1941). The entire Ssese archipelago was once connected to the mainland but was separated when Lake Victoria formed around three-quarters of a million years ago (Davenport et al. 1996). Habitats on Bugala Island are the most modified, but some of the less populated and smaller islands, e.g. Mazinga, are still more intact and natural.

A humid climate is experienced in this IPA throughout the year with slight seasonal variation in humidity, wind, and temperature because it is located in the Lake Victoria zone (Environmental Assessment Consult Limited, 2003; Kalangala District Local Government, 2005). The mean annual rainfall for Ssese islands is 2,180 mm with the heaviest in the periods March-May and November-December. The mean annual minimum temperature is 18°C and the mean maximum annual temperature ranges from 27°C to 30°C.

The Ssese Islands IPA contains a number of Central Forest Reserves that include Lutoboka, Busowe, Towa and Mugoye (Davenport et al. 1996). These reserves are home to a variety of plant and animal life. In particular, Lutoboka CFR is a popular tourist destination, offering visitors the opportunity to go for forest walks, bird watching, and primate viewing. The reserves have, however, suffered much pressure from the need for fuel and charcoal, and therefore logging of trees (Thomas 1941). The steady rise in human population, coupled with the establishment of oil palm plantations and other economic activities caused land use/cover changes in the islands (Davenport et al. 1996, Badui 2018). The improved ferry transport between Bugala Island and the mainland also increased trade in charcoal from the islands (Manyindo 2003).

In the year 2000, the government of Uganda sought the degazettement of 3,500 ha of the c. 6,500 ha of forest reserve gazetted in the 1940s on Bugala island for development of an oil palm estate by BIDCO Oil Refineries Limited. The Environmental Impact Assessment report revealed that the oil palm plantation would escalate deforestation and contribute to the loss of endemic species, increase food insecurity, reduce windbreaks, increase siltation in Lake Victoria, increase water pollution due to use of chemical fertilizers, and reduce the potential for eco-tourism (Environmental Assessment Consult Limited, 2003), but the government went ahead with project implementation despite public resentment and disapproval (Kalangala NGO Forum 2009, Obua et al. 2010). Since then, significant land cover changes have occurred, particularly in Bugala and Bufumira Islands.

A study by Badui (2018) showed that after the establishment of the Vegetable Oil Development Project (VODP); 54%, 41% and 31% of the grassland, woodland and forest cover respectively was lost between 2000 and 2015. The wetlands and subsistence farmland cover lost the least land at 12% and 19% respectively. At a rate of 1,736 ha/year conversion of natural vegetation to palm oil plantation, the latter was projected to become the largest land cover type in Bugala by 2010 (Abonyo et al. 2008). Oil palm plantations surround most of the remaining tropical high forests, creating hard boundaries without buffers that make the forests more vulnerable to edge disturbance (Ssemmanda and Opige 2019). At least one invasive species of plant, Mimosa pigra, occurs in the Ssese Islands IPA. With further disturbance, this species and others may proliferate, altering the species composition and quality of the habitats.
The National Forestry Authority (NFA) has a number of programmes in place to protect the remaining forest estate in this IPA, including tree planting, anti-poaching patrols, and community outreach programmes. However, there are several remaining threats including deforestation, agricultural expansion, and human encroachment. Others are the construction of hotels and lodges, especially on Bugala Island and particularly near Lutoboka. There is thus increasing forest degradation in Bugala and Bufumira including in Lutoboka CFR.
The remaining forests nevertheless represent the best hope for survival of some of the threatened species here. For example, all other sites at which Sabicea entebbensis is known to occur in Uganda, such as Kitubulu forest, are being degraded and undergoing habitat conversion, due to illegal logging and tourism lodge development. The Entebbe area including Kitubulu is rapidly being urbanized, and even Kitubulu CFR has been degraded and is partly being converted into recreation facilities (Gereau et al. 2019). Complete destruction of suitable habitat is presumed to have led to disappearance of sub-populations of this species from Masisi and SW Rwanda (Ntore et al. 2019).

These islands are also important as habitat for a diversity of fauna. Bugala island is estimated to have isolated from the mainland for at least 12,000 years, during which time a rodent species, Pelomys isseli, has evolved on Ssese and Kome islands, and this species, together with the Ssese Island Sitatunga, are the basis for the KBA assessment of Bugala. The Lutoboka woodland reserve is essential for breeding great cormorant (Phalacrocorax carbo), with 5,000 pairs . Other prominent species are Weyns’ Weaver (Ploceus weynsi) and the Northern Brown-throated Weaver (Ploceus castanops), both from the Lake Victoria Basin habitat. Three butterflies are also endemic: Acraea simulata, Thermoniphas togara bugalla and Acraea epaea. The major threat to all these fauna groups is habitat destruction and degradation.

Access and utilization of ecosystem services in Ssese Islands IPA is important for community livelihoods. The services include food production and collection (fruits, hunting and fishing), and fuel (wood or charcoal). Other services include construction materials (timber), medicinal plants, climate regulation and water regulation, grass for cattle and recreation/enjoyment. The most frequently used ecosystem service is the daily use of fuelwood/charcoal for cooking. However, the oil palm plantations have brought adverse impacts to the ecosystem services due to the depletion of the forest and other land cover types (Badui 2018).

The Ssese Islands rely heavily on the Lutoboka CFR for water. The trees in the forest help to control the water cycle and provide habitat for a variety of plant and animal species. The woodland is also a famous tourist destination that helps to support the local economy.

The first exports of robusta coffee as a beverage from Uganda occurred in 1902, mainly from the Ssese Islands. Selection of the ten coffee wilt disease-resistant (CWD-r) clones (KR1 to KR10) is based on material originally collected from indigenous populations in the southern central forests of Uganda, particularly from the forests of Bugala Island, Malabigambo and Mabira, and these now provide the stock for the backbone of modern robusta cultivation in Uganda (Kiwuka et al. 2021, Davis et al. 2023).

Assessed by:

James Kalema, Makerere University Herbarium

Samuel Ojelel, Makerere University Herbarium

Iain Darbyshire, Royal Botanic Gardens, Kew

Date of first assessment: 20th Aug 2024

Reviewed by:

Mary Namaganda, Makerere University