In the biodiversity layer, data on species counts has been used. All data received was in point form i.e. point locations within the landscape. In order to present it as a polygon output in which all data could be represented using a few colors, a grid system was used. With the grid, all data for a specific variable e.g. plants was combined and then grouped into five classes; 1 to 5 with 1 designated for the lowest number (value range) of species and 5 the highest number (value range) of species. A sixth class (class 0) was added to designate all the areas where no data was obtained and areas where the species under consideration did not occur. In the final map, the class 0 areas have been made transparent so that they are not visible on the output map. They all the same exist in the map grid and can be updated once the data becomes available. The conservation status of the different protected areas was also mapped.
The species data, and conservation designation data, were then combined to generate the species richness, species of special importance, conservation status and overall biodiversity maps presented in this atlas. Details of the individual data layers and how the data was summarized are outlined in the subsequent sections.
All the lakes in the graben are rich in fish biodiversity. The large water bodies are Lake George, Lake Edward, Kazinga Channel, Lake Albertand River Semliki. Some of these lakes are the most productive on the African continent (Snoeks, 2000). For example, fifty six fish species are endemic to lakes George and Edward (Plumptre et al, 2007). Fish is an important source of food, livelihood and income to residents within and in the immediate vicinity of the graben. The most widely distributed fish species in the graben are; Oreochromis niloticus (the Nile tilapia/ ‘Ngege’), Bagrus docmak (Catfish/‘Semutundu’), Protopterus aethiopicus (Lung fish/‘Mamba’) and Clarias gariepinus (Mud fish/‘Male’) and over 50 species of Haplochromine species (‘Nkejje’) dominating the fish biomass in all the lakes. Other fish species of less commercial importance but of high nutritional value, occurring in small numbers in all lakes of the graben include Barbus spp, Mormyrus spp and Labeo spp.
In terms of fish species richness, Lake Albertranks highest among the Albertine Graben lakes. Some species e.g. Alestes baremose (‘Angara’) Malapterurus electricus (Electric Cat fish), Hydrocynus forskahlii (Tiger fish /’Ngassa), Distichodus niloticus and Brycynus nurse (‘Muzri’) are endemic to Lake Albert.
Catch Assessment Survey (CAS) data collected from Lake Albert and Lake Edward by National Fisheries Resources Institute (NaFIRRI,) in 2006 and 2008 respectively indicates that there is predominance of fish juveniles and brood stock (female egg bearing fishes) in shallow inshore waters, sheltered areas (lagoons and bays), river mouths and rocky areas. Other fish species e.g. Barbus altianalis and Clarias gariepinus are anadromous i.e. they migrate upstream into rivers and streams to breed and spawn in riverine wetlands. There are also fish species that breed and spawn in the open deep waters. Their juveniles swim to shallow, sheltered, food-rich and less predation prone areas.
The Sensitivity of fisheries resources to petroleum development is associated withhigh frequency noise from petroleum development activities e.g. offshore seismic shots, exploration drilling in fish habitats and fishing grounds.The sensitivity is also associated with oil spills, and pollution from hydrocarbon compounds and chemicals from mud cuttings. These can cause drastic change in aquatic environment leading to migration or death of fish. This would lead to changes in fish species distribution, composition and diversity.
Data obtained covers Lake Albert, parts of Lake Edward, Kazinga Channel andLake George, and parts of River Nile. Generally, the areas of Lake Edward, Kazinga Channel and Lake George showed the highest biodiversity (Figure 1) followed by Lake Albert. For Lake Albert, the delta area of River Nile, occurring inMurchisonFallsNational Park, areas around Kabwoya and the south-most tip of the lake registered the highest fish species counts.
Large mammals and crocodiles distribution in the Albertine Rift
Although most large mammals (elephants, lions, buffalos etc) occur in protected areas, a few are found outside the protected areas. The status of biological resources within protected areas has, therefore, been better researched than outside protected areas. So most of the data used in this sensitivity atlas was collected from within protected areas. For QENP, Toro-Semliki WR and MFCA, aerial survey data was used. For Kabwoya WR, Kaiso-tonya Wildlife Area and Bwindi NP, systematic ground survey data was used. The data collected by rangers and entered into Management Information System (MIST) for analysis was used for the rest of the protected areas.
Although mammals occur throughout protected areas, none were observed in some areas at the time of the survey. This does not imply that there are no animals in such areas. The populations may be very low, seasonal or the animals could have moved to parts of the protected area at the time of data collection. On the other hand, there are areas which have higher animal concentrations than others on a permanent and seasonal basis. Such areas, if explored, should be handled with maximum care to ensure sustainable conservation of the biodiversity therein. For example the delta region of MFNP, which is also a Ramsar site has permanently higher large and small mammals concentrations compared to other parts of the park. Other areas e.g. Bwindi Impenetrable NP and the Ishasha sector of QENP may have fewer mammals but these mammals are either of unique character or are highly restricted in habitat range. For example, inUgandathe Mountain gorilla only occurs in Bwindi Impenetrable NP and Mgahinga NP (Figure 2.2). Such areas attract the highest number of tourists to the region.
At the time of preparation of this atlas, information on breeding areas, watering points and feeding areas was not yet available. These data gaps require further basic research to enrich upcoming editions of the sensitivity atlas.
The delta area of Murchison NP showed the highest mammal counts (Figure 2.4). The central part of Queen Elizabeth NP and its southern part also showed high mammal counts.
Woody plants and bird species
The Albertine Graben has a high biodiversity of bird species. Over fifty percent of the total African birds are found in the Albertine graben. There are also a number of important Bird Areas (IBAs) in the graben. The 30 Important Bird Areas (IBAs) in Ugandaoccupy some 8% of the land surface of the country and include a wide variety of forest, savanna and wetland habitats (Byaruhanga et al. 2001). The IBA network captures 73% of the total birds species found inUganda and 82% of those of highest conservation priority species i.e. endemic to the Albertine graben.QueenElizabethNational Park has important migratory birds stopping points for birds coming fromEurope along the African-Eurasian flyway.
By 2007, 5793 plant species had been recorded within the Albertine Rift. This forms 14% of all mainland Africa’s plant species. So far 551 endemic plant species have been identified in the Albertine Rift (Plumptre et al. 2007).
The birds and woody plants species data was collected at the same time. Each landscape, where data was collected, was divided into blocks. Data was then collected along transects in each block. The total species in each block was computed. These total numbers are presented in this Atlas. Whereas data for Queen Elizabeth NP was still being processed at the time of preparation of this report and so it is not presented in this map, there is no complete birds and plants data set available for Murchison Falls NP.
Bwindi Impenetrable NP registered the highest birds species numbers (Figure 2.6). Bugoma FR, Maramagambo FR and a large part of Budongo FR also registered high birds species counts. The small areas scattered over the whole graben that registered high numbers are the permanent data collection areas monitored by Makerere University Institute of Environment and Natural Resources (MUIENR).
Kibale NP registered the highest species counts followed by Budongo FR and Bugoma FR (Figure 2.7). Data for Queen Elizabeth NP and for Murchison Falls NP was incomplete.
Sensitivity based on endemic and threatened species
Uganda’s Albertine graben is a global centre of species endemism (biological resources that can’t be found anywhere else in the world). The Albertine Rift harbours more endemic mammals, birds and amphibians than any other region on the African continent (Conservation international). Birdlife International also recognizes the Albertine graben as an Endemic Bird Area (Stattersfield et al, 1998). Among the protected areas in the Albertine Rift, Bwindi Impenetrable and Mt. Rwenzori National parks rank second and third respectively in number of endemic mammal species (Plumptre et al, 2007). There are seven (7) phytochoria or regional centers of endemism including; Guinea-Congolian; Sudanian; Afromontane/Archipelago and L. Victoria Regional Mosaic among others (White, 1979). White (1983, 1993) classified the Albertine Rift as part of the Guinea-Congolian center of endemism. There are, unfortunately, a number of species that are threatened. By 2007, twenty five (25) species occurring in the Albertine Rift were threatened. Of these, thirteen (13) are endemic. Figure 2.8 shows the giant Lobelia, a plant endemic to the high altitude areas of the Albertine rift.
Data on endemic and threatened birds and plants was obtained for forested areas (National parks andForestreserves). Although the compilation of data is not complete for all areas, there are some areas in which no endemic species have been encountered. No endemic birds were found in Kashoha-kitomi FR, Kibaale NP, Semliki NP, Bugoma FR, and Budongo FR. There were also no threatened bird species encountered in Echuya FR, Kashoha-Kitomi FR, Kibale NP, most parts of Semliki NP, the southern part of Rwenzori NP, the northern part of Budongo FR. Although no endemism was recorded for the large mammals, there exists endemic mammals in the Albertine rift, especially among the smaller mammals e.g. Red duiker found inMt.RwenzoriandBwindiImpenetrableNational Parks. It should be noted that smaller mammals were not considered in this atlas due to the limited coverage of the available data.
Whereas Mgahinga NP registered very high birds species endemism all over the area,Mt.Rwenzoriand Bwindi Impenetrable national parks registered varying levels of birds endemism (Figure 2.9). Some of the areas had very high values. Of the forested areas, Budongo and Bugoma forest reserves registered endemic birds presence.
The whole of Mgahinga NP registered high plants species endemism (Figure 2.10). Parts of Bwindi Impenetrable andMountRwenzorinational parks also registered high plants species endemism. Of the forest reserves, Bugoma FR registered the highest plants species endemism.
Bwindi Impenetrable NP registered the highest numbers of threatened birds species distribution (Figure 2.11). Other parks that registered endemic birds presence were Mgahinga, Mount Rwenzori and Semliki NP. Budongo and Bugoma forest reserves also registered presence of threatened plant species.