Semuliki National Park
Not all forests are equal and Semuliki National Park, with its unique conservation value (see below) must be continued to be protected and enhanced. Preserving areas of high conservation significance is critical as any loss in these areas will result in a disproportionate loss of species' distributions, especially narrow-range endemics, elevating a species' risk of extinction.
The old growth primary forest of Cynometra alexandri stands contained within the eastern section of Semuliki National Park and the naturally regenerated and re-established secondary forest to the west of the park, have created an ecologically mature and biodiverse forest ecosystem. The park lies within the Guineo-Congolian centre of endemism, within the biodiversity hotspot of the Western Rift Valley (Albertine Rift), which extends from the northern point of Lake Albert to the southern end of Lake Tanganyika. The mountainous region and valleys of the Albertine Rift are bordered to the west by the Ituri Forest of the DRC, to the east by four of the African Great Lakes (Albert, Edward, Kivu and Tanganyika) and to the south by a large zone of tropical deciduous and bush vegetation. Extensive tectonic movements and geomorphological change that occurred throughout the Pliocene and Pleistocene, with often parallel events occurring in the Lake Albert and Lake Edward regions and which created the upheaval of the Rwenzori Mountains; the formation of Lake Edward and the establishment of the Semliki as a permanent river, has produced the dramatic landscape we see today (Stewart, 2004).
Lying at a maximum altitude of 760 m, the landscape provides distinct Guineo-Congolian species concentrations and distributions, especially of butterfly species - many at the eastern extent of their range distribution. The park's proximity to the Congo Basin and the second largest tract of tropical forest in the world, bordering the Ituri Forest of the DRC across the Semliki River, should be a reason to be optimistic. However, with the general lack of landscape-level conservation or sustainable management within the DRC and the continuing degradation of forest across the Semliki River, makes the park's conservation significance and conservation focus even greater. Any decrease in the park's forest area or increase in pressures or patch isolation (with the Ituri Forest) will reduce insect and plant abundance from anywhere between 20 to 75 percent (Haddad et al., 2015) with the associated detrimental effect on ecological functions and forest structure, reducing ecosystem services
Semuliki National Park, with an area of 219 km² is Uganda’s only remaining lowland rainforest. It is located within Bundibugyo district,
approximately 60 km south‐west of Lake Albert and 40 km north‐west of Fort Portal. Much of the park is flat, lying at an altitude of 670 m to the east and rising to undulating sections of 760 m at its western boundary and lying within the 160 km long Semliki Valley, which stretches from the shores of Lake Edward to the shores of Lake Albert. To the east of the park is a demarcated point where the rainforest is supplanted by open grasslands. The majority of the Semliki Valley is situated within the DRC with only a small area located in Uganda to the north-east. The park is bounded to the north‐northwest by the steep escarpment of the Rwenzori Mountain Range, isolating the park from the rest of East Africa. The northern boundary is the Semliki River, the international boundary between Uganda and the DRC. This river flows north from Lake Edward, carrying water from the Virungas and Rwenzori mountain ranges through the Rift valley floor to Lake Albert. To the west the Lamia river borders the park and is also a DRC border crossing.
At the landscape level, there are numerous small areas of sub‐habitats due to previous land practices. These are predominantly to the west of the park and differences in soil hydrology causes water‐logging to the east of the park. Canopy closure is consistently high as the secondary forest has been allowed to naturally regenerate from forest degradation in the past. The climax communities of the monodominant forest areas in Semuliki are characterised by the single semi‐deciduous tree species, Cynometra alexandri. This has no common commercial value; a long‐ life span and can grow on a variety of soil substrates, including the halomorphic clay soils found at Semuliki. Within this monodominant association, the narrow conical crowns within this stratum are densely packed with little canopy gaps, and this creates the shady conditions on the forest floor and understorey preferred by lowland, forest‐dependant butterfly species.
Semuliki National Park, showing connectedness to the Congo Basin forests of the DRC (terraPulse, 2021).
Semuliki National Park, showing forest remnants to the east - darker green (Google Maps, 2015).
Forest trail showing the shadow of the forest floor and canopy closure.
While lowland Afrotropical forests like Semuliki and elsewhere in the Congo Basin are butterfly species-rich , these species are inclined to have large distributions and ranges extending to the equatorial forests further west. This can result in a lower contribution of any individual location to the overall distributions of these species. However, any biodiversity significance of an area combines spatial variation in both species richness and levels of endemism, and hence indicates the relative contribution of a location to the persistence of forest species (Hill et al., 2019).
Identifying and then quantifying a site's conservation importance, to target and prioritise conservation efforts, have included a number of methodologies, each with its own limitations. In general, biodiversity significance is higher within the tropics, especially areas with topographically heterogenous habitat, like Semuliki and with biodiversity intactness. However, within each approach taken to measure a site's conservation significance, Semuliki National Park has always been included as an example using each of the metrics measured by the, to date, most credible approaches used.
Using a scoring methodology evaluating the conservation value by assessing three traits; the effective contribution of the individual protected area; effective protection for the biogeographic unit and a priority for action, Howard (1991) evaluated Semuliki along with twelve other Ugandan national parks and forest reserves. Four groups of animals and plants (forest trees, forest birds, diurnal forest primates and 71 species of forest butterfly from two genera; Charaxes and Papilios) were used as indicator species for evaluating the conservation importance of each site. Species lists from each site for each group, focusing on richness and rarity value were used to derive an ‘importance for conservation’ score for each forest. Semuliki recorded 51 of the 71 butterfly species that were used as forest indicator species. This was second only to Bwindi Impenetrable National Park and it was concluded that these two Ugandan parks were considered to have the greatest conservation value for the four groups assessed.
In 2004, Semuliki National Park was identified as a priority site for conservation measures, being located within the Albertine Rift and the Eastern Afromontane biodiversity hotspot region. In 2012, it was assessed by Birdlife International as being an important bird and biodiversity area (IBA); meeting three of the four IBA criteria, containing one of the richest localities for forest birds in Africa (BirdLife International, 2021). A year later in 2013, the park was placed 2984th in an evaluation of 173,461 global protected areas from the contribution each protected area provided to the long-term survival of evaluated species groups. Most recently in 2016, the park was included by the International Union for the Conservation of Nature (IUCN) as one of the Key Biodiversity Areas (KBA) which requires a site to meet one or more of eleven criteria, grouped into five categories; ecological integrity, biological processes, irreplaceability, geographically restricted biodiversity and threatened biodiversity.
Forest biodiversity significance and intactness in the Congo Basin region (including Semuliki National Park) showing high values (dark green) of both metrics for the park (Image adapted from Hill et al. 2019).
Biodiversity hotspots outlined in black (Hoffman et al., 2016). Semuliki NP included within the Eastern Afromontane biodiversity hotspot. The dark green colour (including Semuliki) represents Guineo-Congolian evergreen and semi-evergreen forest habitat (Sayre et al., 2013).
High intactness is important for a number of reasons: to maintain ecosystem functioning; retain community resilience against pressures such as climate change and especially for forest ecosystems, to mitigate climate change (Steffen et al., 2015). However, the landscape surrounding the park is under imminent threat and this regional change, particularly across the border in the DRC can seriously affect ecosystem stability at Semuliki and subsequently its biodiversity. So, biodiversity intactness which includes species richness is especially relevant when defining wilderness regions and intact forest landscapes (Watson et al.,2018).
Protected reserves and forest loss in the DRC is continually increasing and this culminated in a rate of increase 2.5 times greater for each year from 2011-2014 (Minnemeyer et al., 2017) than compared to the years from 2010-2014. The lack of any effective governance in the DRC and enforcement of environmental regulations is promoting an emerging number of regional deforestation hotspots which are now intersecting the remaining primary forest. Semuliki being an important tropical lowland forest in Uganda, harbouring Guineo-Congolian dominated species within East Africa is now becoming increasingly isolated within a patchwork of anthropogenic-influenced habitat changes that are surrounding it to the north and west. These hotspots are primarily concentrated to the south-west of Semuliki, radiating out from the town of Beni in the eastern province of North Kivu in the DRC. There is also increasing fragmentation of the Ituri forest in the DRC across the Semliki River which continues to the north-west and into the Parque Nationale du Virungas.
The drivers of this new regional deforestation threat to the forests are not subsistence farmers, where the continual international focus on increasing existing crop yields and thereby reducing pressure for the conversion of more forest for agricultural use appears to be working. This new source is wealthier farmers clearing land to earn extra income and creating a larger more commercial scale of agriculture from the extra forest being cleared (Moonen et al., 2016).
Regional deforestation hotspots from 2000-2014 in the DRC, surrounding Semuliki National Park (Minnemeyer et al., 2017).
In addition to habitat degradation in Africa's tropical forests, further pressures on forest‐dependant species will be exacerbated by future changes in climate. With the absence of a latitudinal temperature gradient within the tropics, pole‐ward migration of elevation restricted species is not possible (Wright et. al., 2009) without being exposed to more extreme temperatures than normally experienced. The behavioural and physiological pre‐adaptation of some temperate species to allow rapid range shifts due to past historical glacial retreats (Willig et al., 2003) is predicted to be uncommon in tropical species due to the climate and ecosystem remaining relatively stable over time. This has created narrow thermal niches and restricted range distributions of many butterfly species seen today at Semuliki National Park (Janzen, 1967).
Currently, the range and dispersal capacity of these species in the tropical forests of Africa remains poorly understood and the host plants for several of these forest‐restricted fruit-feeding butterfly species are also unknown. This behaviour, together with host plant distribution, will have an influence on their ability to survive the possibility of major anthropogenic disturbances in the future (Marchant et al., 2015). Tropical species can also be dependant on tight inter-specific interactions for dispersal and reproduction (Bawa, 1990) which also increases the difficulty for species migrations.
Semuliki was designated a national park in 1994 and administered initially under the auspices of a governmental department, the Uganda Game and Fisheries Department. Since 1996, it has been administered by the Uganda Wildlife Authority (UWA), an amalgamation of Uganda’s National Park’s and Game and Fisheries departments. The remit of UWA is to ‘conserve, economically develop and sustainably manage the wildlife and protected areas of Uganda in partnership with neighbouring communities and stakeholders for the benefit of the people of Uganda and the global community’.
There are a number of strategies that can be undertaken to conserve Semuliki's forest landscape and butterflies from a changing climate. The most important is the continuing conservation of the forest as expanding the existing habitat with it's geographical isolation, surrounding grassland vegetation of the Semliki Valley, border with the DRC and its degraded forest together with the topographical impediment of the Rwenzori Mountain Range, both preclude forest connectivity and also make range shifts difficult. Conservation in situ can be the promotion of microclimate heterogeneity, allowing a greater diversity of habitat options providing climate vegetation refuges for butterfly and other insect species to exploit as the climate changes.
For further information on UWA: www.ugandawildlife.org
Key Biodiversity Areas: www.keybiodiversityareas.org/site/factsheet/7049
A conservation action plan for the Albertine Rift can be downloaded here:
Its category as a protected area irreplaceability: https://irreplaceability.cefe.cnrs.fr/sites/40042
Its inclusion as part of the Eastern Afromontane Biodiversity Hotspot: https://www.cepf.net/our-work/biodiversity-hotspots/eastern-afromontane
Semuliki National Park references:
Davenport, T. and Howard, P. C., (1996). Semliki Biodiversity Report, Forest Department, Kampala. Includes a chapter on butterflies and large moths the authors recorded at Semuliki.
Howard, P.C., (1991). Nature conservation in Uganda’s Tropical Forest Reserves, International Union for the Conservation of Nature and WorldWide Fund for Nature, Gland and Cambridge. Includes a checklist of the forest butterflies of the family Papilionidae and the Charaxes genus from the Nymphalidae, recorded at Semuliki and another 11 forest reserves and parks.
Johnston, H., (1902). The Uganda Protectorate, Ruwenzori, and the Semliki Forest. The Geographical Journal 19, 1-39. A historical record of the area.
Website text references:
Bawa, K.S., (1990). Plant‐pollinator interactions in the tropical rain forests. Annual Review of Ecology and Systematics 21, 399‐422.
BirdLife International, (2021). Important Bird Areas factsheet: Semliki National Park.
Haddad, N.M., Brudvig, L.A., Clobert, J., Davies, K.F., Gonzalez, A., Holt, R.D., Lovejoy, T.E. et al. (2015). Habitat fragmentation and its lasting impact on Earth’s ecosystems. Science Advances. DOI: 10.1126/sciadv.1500052.
Hill, S.L.L., Arnell, A., Maney, C., Butchart, S.H.M., Hilton-Taylor, C., Ciciarelli, C., Davis, C., Dinerstein, E., Purvis, A. & Burgess, N.D. 2019. Measuring forest biodiversity status and changes globally. Frontiers in Forest and Global Change, (2) 70.
Hoffman, M., Koenig, K., Bunting, G., Costanza, J. & Williams, K.J., (2016). Biodiversity Hotspots (Version 2016.1), (doi: 10.5281/zenodo.3261807).
Janzen, D.H., (1967). Why mountain passes are higher in the tropics. The American Naturalist 101, 233‐249.
Marchant, N.C., Purwanto, A., Harsanto, F.A., Boyd, N.S., Harrison, M.E. & Houlihan, P.R., (2015). ‘Random flight’ dispersal in tropical fruit‐feeding butterflies? High mobility, long lifespans and no home ranges. Ecological Entomology 40, 696‐706.
Minnemeyer, S., Goldman, E.D. & Harris, N., (2017). ‘New deforestation hotspots in the world’s largest tropical forests’, in World Resources Institute, from http://www.wri.org/blog/2017/02/new‐deforestation‐hotspots‐worlds‐largest‐tropicalforests.
Moonen, P. C., Verbist, B., Schaepherders, J., Meyi, M. B., Van Rompaey, A. & Muys, B., (2016). Actor‐based identification of deforestation drivers paves the road to effective REDD+ in DR Congo. Land Use Policy 58, 123‐132.
Plumptre, Ayebare, S., Behangana, M. et al., (2018). Conservation of vertebrates and plants in Uganda: Identifying Key Biodiversity Areas and other sites of national importance. Conservation Science and Practice 1:e7.
Sayre, R. G., Comer, P., Hak, J., Josse, C., Bow, J., Warner, H., Larwanou, M., Kelbessa, E., Bekele, T., Kehl, H., Amena, R., Andriamasimanana, R., Ba, T., Benson, L., Boucher, T., et al. (2013). A new map of standardized terrestrial ecosystems of Africa. African Geographical Review, 32, 1– 24.
Steffen, W., Richardson, K., Rockström, J., Cornell, S. E., Fetzer, I., Bennett, E. M., et al. (2015). Planetary boundaries: guiding human development on a changing planet. Science 34.
Stewart, K.M., (2004).Revisiting the Senga 5a Fish Fauna, Upper Semliki River, Democratic Republic of Congo. Archaeofauna 13, 145-154.
Watson, J. E. M., Venter, O., Lee, J., Jones, K. R., Robinson, J. G., Possingham, H. P., et al. (2018). Protect the last of the wild. Nature 7729, 27–30.
Willig, M.R., Kaufman, D.M. & Stevens, R.D., (2003). Latitudinal gradients of biodiversity: pattern, process, scale and synthesis. Ecology, Evolution and Systematics 34, 273‐309.
Wright, S.J., Muller‐Landau, H.C. & Schipper, J., (2009). The future of tropical species on a warmer planet. Conservation Biology 23, 1418‐1426.