Eastern Arc Forests Research Articles

Kimboza, a Small Lowland Forest With an Outstanding Herpetofauna Diversity in East Africa.

The Eastern Arc Mountains (EAM) and Coastal forests of Tanzania are renowned for harboring large number of threatened and endemic vertebrate species, yet most of these areas have been partially studied. The Kimboza Nature Forest Reserve (KNFR) is a small forest which is in transition between the EAM and Coastal forests, and among the poorly surveyed areas for amphibians and reptiles. We conducted systematic surveys across the KNFR in 2012 and between 2020 and 2023 using a range of approaches with the aim of establishing a comprehensive and updated list of reptile and amphibian species and assess the contribution of EAM and Coastal forests to the KNFR's herpetofauna. We identified 77 species, 29 amphibians and 48 reptiles, substantially updating previous species lists. Three of these species (Kinyongia magomberae, Trachylepis boulengeri and Philothamnus macrops) represent range extensions from previously known ranges. Fourteen species are endemic to East Africa, 11 of them being restricted to Tanzania. These results make the KNFR the richest forest reserve for herpetofauna per square km in Tanzania, and most similar in its composition to the Coastal, rather than Eastern Arc forests. With the caveats concerning taxonomic uncertainties and the inequalities of sampling intensity across the region, this study shows that the KNFR is an important area that deserves conservation attention. The KNFR, like other Coastal forests, is under significant pressure from anthropogenic activities which call for an urgent action to protect this small but rich forest.

Mapping Natural Forest Remnants with Multi-Source and Multi-Temporal Remote Sensing Data for More Informed Management of Global Biodiversity Hotspots

Global terrestrial biodiversity hotspots (GBH) represent areas featuring exceptional concentrations of endemism and habitat loss in the world. Unfortunately, geospatial data of natural habitats of the GBHs are often outdated, imprecise, and coarse, and need updating for improved management and protection actions. Recent developments in satellite image availability, combined with enhanced machine learning algorithms and computing capacity, enable cost-efficient updating of geospatial information of these already severely fragmented habitats. This study aimed to develop a more accurate method for mapping closed canopy evergreen natural forest (CCEF) of the Eastern Arc Mountains (EAM) ecoregion in Tanzania and Kenya, and to update the knowledge on its spatial extent, level of fragmentation, and conservation status. We tested 1023 model possibilities stemming from a combination of Sentinel-1 (S1) and Sentinel-2 (S2) satellite imagery, spatial texture of S1 and S2, seasonality derived from Landsat-8 time series, and topographic information, using random forest modelling approach. We compared the best CCEF model with existing spatial forest products from the EAM through independent accuracy assessment. Finally, the CCEF model was used to estimate the fragmentation and conservation coverage of the EAM. The CCEF model has moderate accuracy measured in True Skill Statistic (0.57), and it clearly outperforms other similar products from the region. Based on this model, there are about 296,000 ha of Eastern Arc Forests (EAF) left. Furthermore, acknowledging small forest fragments (1–10 ha) implies that the EAFs are more fragmented than previously considered. Currently, the official protection of EAFs is disproportionally targeting well-studied mountain blocks, while less known areas and small fragments are underrepresented in the protected area network. Thus, the generated CCEF model should be used to design updates and more informed and detailed conservation allocation plans to balance this situation. The results highlight that spatial texture of S2, seasonality, and topography are the most important variables describing the EAFs, while spatial texture of S1 increases the model performance slightly. All in all, our work demonstrates that recent developments in Earth observation allows significant enhancements in mapping, which should be utilized in areas with outstanding biodiversity values for better forest and conservation planning.

Impact of habitat fragmentation on the spatial structure of the Eastern Arc forests in East Africa: implications for biodiversity conservation

The Eastern Arc Mountains in Tanzania and Kenya are one of 35 global biodiversity hotspots. The Eastern Arc forests are, as are many other tropical biodiversity hotspots, highly fragmented. Understanding the impact of habitat fragmentation (i.e., habitat loss and subdivision) on the spatial structure of the Eastern Arc forests is important because forest spatial structure highly influences species richness, persistence, and extinction debt. Here we examine the impact of habitat fragmentation on the spatial structure of the Eastern Arc forests at a patch scale using very high resolution aerial imagery having a spatial resolution of 0.5–1.5 m. Forest area across the 13 Eastern Arc Mountains is 405,852 ha and is distributed into 311 fragments ≥ 10 ha in size with a median fragment size of 84 ha. The 18 largest forest fragments in the Eastern Arc Mountains contain greater than three-quarters of total forest area. Average fragment isolation, as assessed by median distance to nearest fragment and median distance to the nearest larger fragment, is 867 and 1533 m, respectively. Of total forest area, 14% is < 100 m from the forest edge and 33% is < 300 m from the forest edge. Establishing forested linkages among the largest and closest forest fragments through forest regeneration and protection of secondary regenerating forest as well as providing protected area status to the remaining non-protected forest including unprotected smaller forest fragments are important to enhancing the long-term persistence of many plant and animal species here.

Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates.

Conservation actions need to be prioritized, often taking into account species' extinction risk. The International Union for Conservation of Nature (IUCN) Red List provides an accepted, objective framework for the assessment of extinction risk. Assessments based on data collected in the field are the best option, but the field data to base these on are often limited. Information collected through remote sensing can be used in place of field data to inform assessments. Forests are perhaps the best-studied land-cover type for use of remote-sensing data. Using an open-access 30-m resolution map of tree cover and its change between 2000 and 2012, we assessed the extent of forest cover and loss within the distributions of 11,186 forest-dependent amphibians, birds, and mammals worldwide. For 16 species, forest loss resulted in an elevated extinction risk under red-list criterion A, owing to inferred rapid population declines. This number increased to 23 when data-deficient species (i.e., those with insufficient information for evaluation) were included. Under red-list criterion B2, 484 species (855 when data-deficient species were included) were considered at elevated extinction risk, owing to restricted areas of occupancy resulting from little forest cover remaining within their ranges. The proportion of species of conservation concern would increase by 32.8% for amphibians, 15.1% for birds, and 24.7% for mammals if our suggested uplistings are accepted. Central America, the Northern Andes, Madagascar, the Eastern Arc forests in Africa, and the islands of Southeast Asia are hotspots for these species. Our results illustrate the utility of satellite imagery for global extinction-risk assessment and measurement of progress toward international environmental agreement targets.

Globally Threatened Dragonflies (Odonata) in Eastern Africa and Implications for Conservation

ABSTRACT This paper presents the status of East African dragonfly species (Odonata) listed globally as threatened on “The IUCN Red List of Threatened Species”. The area considered includes Ethiopia, Kenya, Uganda, Burundi, Rwanda, Tanzania and Malawi. From a total of 323 species known from these countries, 31 are listed in one of the categories “Near Threatened”, “Vulnerable”, “Endangered” and “Critically Endangered”, while nine are marked as “Data Deficient”. Ecoregions with high numbers of threatened species are the Ethiopian and East African montane forests, Eastern Arc forests and Northern Zanzibar-Inhambane coastal forest mosaic. The highest species diversity is found in the Albertine Rift montane forests ecoregion. Information concerning the distribution, conservation status and biology of these species is given and conservation issues are discussed.

Can distribution models help refine inventory‐based estimates of conservation priority? A case study in the Eastern Arc forests of Tanzania and Kenya

AbstractAim Data shortages mean that conservation priorities can be highly sensitive to historical patterns of exploration. Here, we investigate the potential of regionally focussed species distribution models to elucidate fine‐scale patterns of richness, rarity and endemism.Location Eastern Arc Mountains, Tanzania and Kenya.Methods Generalized additive models and land cover data are used to estimate the distributions of 452 forest plant taxa (trees, lianas, shrubs and herbs). Presence records from a newly compiled database are regressed against environmental variables in a stepwise multimodel. Estimates of occurrence in forest patches are collated across target groups and analysed alongside inventory‐based estimates of conservation priority.Results Predicted richness is higher than observed richness, with the biggest disparities in regions that have had the least research. North Pare and Nguu in particular are predicted to be more important than the inventory data suggest. Environmental conditions in parts of Nguru could support as many range‐restricted and endemic taxa as Uluguru, although realized niches are subject to unknown colonization histories. Concentrations of rare plants are especially high in the Usambaras, a pattern mediated in models by moisture indices, whilst overall richness is better explained by temperature gradients. Tree data dominate the botanical inventory; we find that priorities based on other growth forms might favour the mountains in a different order.Main conclusions Distribution models can provide conservation planning with high‐resolution estimates of richness in well‐researched areas, and predictive estimates of conservation importance elsewhere. Spatial and taxonomic biases in the data are essential considerations, as is the spatial scale used for models. We caution that predictive estimates are most uncertain for the species of highest conservation concern, and advocate using models and targeted field assessments iteratively to refine our understanding of which areas should be prioritised for conservation.

Forest History in East Africa's Eastern Arc Mountains: Biological Science and the Uses of History

In this article, I argue that conservation science in its role of advocate for the natural world could profitably draw from site-specific histories that integrate human and natural histories. Both fields analyze the dynamic interaction of structure and process. In East Africa's Eastern Arc Mountains, where forests contain high levels of species endemism and biological diversity, the prevailing historical paradigm from conservation science represents today's forests as surviving fragments of much larger forests. This view builds upon a century-long tradition of scientific scholarship that has developed theories for the evolution of Eastern Arc forests that encompass geological time scales. However, the relatively brief, millennialscale land-use history of the mountains, insofar as it is currently understood, suggests that human manipulation of forest biota involved periods of deforestation and regeneration, as well as the introduction of exotic plants.

Late Quaternary vegetation dynamics in a biodiversity hotspot, the Uluguru Mountains of Tanzania

Late Quaternary vegetation history and environmental changes in a biodiverse tropical ecosystem are inferred from pollen, charcoal and carbon isotope evidence derived from a ∼ 48,000-yr sedimentary record from the Uluguru Mountains, a component of the Eastern Arc Mountains of Kenya and Tanzania. Results indicate that Eastern Arc forest composition has remained relatively stable during the past ∼ 48,000 yr. Long-term environmental stability of the Eastern Arc forests has been proposed as a mechanism for the accumulation and persistence of species during glacial periods, thus resulting in the diverse forests observed today. The pollen and isotope data presented here indicate some marked changes in abundance but no significant loss in moist forest taxa through the last glacial maximum, thereby providing support for the long-term environmental stability of the Eastern Arc. Anthropogenic activities, including burning and forest clearance, were found to play a moderate role in shaping the mosaic of forest patches and high-altitude grasslands that characterise the site today; however, this influence was tempered by the inaccessibility of the mountain.

Joint Forest Management In Chome Catchment Forest Reserve, Tanzania: The Role Of Socio-Economic And Institutional Factors In Determining Sustainable Forest Conservation

This study was conducted in Chome Catchment Forest Reserve, South Pare Mountains, Tanzania to assess the role of ecological, socio-economic and institutional factors in determining successful implementation of the Joint Forest Management approach. Data were collected through participatory rural appraisal techniques, household questionnaire surveys and key informant interviews. Data on timber resources were based on existing inventories and direct observations. It was observed that the volume of timber resources in the forest is among the highest known for the Eastern Arc forests. Over 72% of this volume consists of high value timber species, making this resource an extremely desirable option for income generation. Household income is at par with other Eastern Arc areas but existing land scarcity is relatively higher. Household plot sizes tend to be as small as (>0.44 ha) with population density of about 13 persons ha-1. Farm plot fragmentation through inheritance is also high. Limited livelihood options, high timber demands and poor resources accessibility are the major drivers of illegal timber harvesting in the reserve by adjacent communities. Illegal timber harvesting was estimated at 100.7 thousand m3 per annum between 1998 and 2001. The implementation of joint forest management, centered on Village Environmental Councils, lacks clear guidelines on institutional responsibilities and duties leading to its failure. A number of other factors including corruption, policing difficulties and inadequate benefit sharing contribute to management failure. It is recommended that joint forest management be developed and implemented in a holistic framework which promotes alternative livelihood options; reduce dependency on forest-based income and strength institutional structures through legal frameworks. It is proposed that the forest sector expand its management approach through adopting a multi-disciplinary approach which incorporates external sectors, particularly agriculture. TJFNC Vol. 76 2007: pp. 1-10

Monitoring the health of selected eastern arc forests in Tanzania

AbstractThe eastern arc mountains (EAMs) are a chain of isolated mountains (534,000 ha) in Kenya and Tanzania surrounded by arid woodlands and influenced by the Indian Ocean. In 1900 there was three times the amount of forest cover there is today. Much of the original forests have been converted into agricultural crops. These mountains are recognized as a globally important ‘hot spot’ by World Wide Fund for Nature (WWF) and World Conservation of Union (IUCN) for forest biodiversity and are major national, regional and local sources of hydropower, water and wide array of forest‐based benefits and agricultural production. In February 2000 we began a 3‐year evaluation of forest health, land‐use change and information sharing in the EAMs. Permanent sample plots were used to evaluate forest health. This paper summarizes the baseline data from eighteen permanent sample plots in the east Usambara's and nine in Ulugurus. The eastern arc web site (http://www.easternarc.org) was established, continues to expand and contains some detailed information on the project. Information gathered will assist land managers, planners, policy makers, interested communities (villages) and individuals in decision‐making. These data can also provide an early warning system of stresses on forest catchments.

Critical species of Odonata in eastern Africa

Abstract From eastern Africa, ranging from Somalia and Ethiopia south to Mozambique and Zimbabwe and west to eastern Democratic Republic of Congo and Botswana, ca 500 species of Odonata are known. Comments on species and sites of conservation concern are given as well as recommendations for future research and conservation activities. Due to the rapid and ongoing destruction of forests, especially of coastal, Guineo-Congolian and Eastern Arc forests, species confined to these habitats are the most threatened.

Seven new montane species of Drosophila in the Eastern Arc mountains and Mt Kilimanjaro in Tanzania attesting to past connections between eastern and western African mountains (Diptera: Drosophilidae)

This report describes 7 new species of Drosophila found in the Eastern Arc mountains and on Mount Kilimanjaro in Tanzania: D. baucipyga, D. gata, D. kilimanjarica, D. neogata, D. paragata, D. pilocornuta and D. usambarensis spp.n. Two new species complexes, the megapyga species complex (Sophophora subgenus, melanogaster group, montium subgroup) and the gata species complex (Drosophila subgenus) are introduced. Only one species, D. baucipyga of the montium subgroup, has a geographical range matching the whole Eastern Arc, from the Usambara Mts. in the north-east of Tanzania to Mt. Uzungwa in the south-south west of the country. Five others, including one representative of the dentissima group of the Sophophora subgenus, D. usambarensis, and four representatives of the Drosophila subgenus, D. gata, D. neogata, D. paragata and D. pilocornuta, were found only in the Usambara Mts. Two of these five, D. usambarensis and D. pilocornuta were found only in West-Usambara, while two other related species, D. gata and D. paragata, were found only in East-Usambara. Only the distribution of D. neogata covers the whole of the Usambara mountains. Outside the Eastern Arc, another representative of the dentissima group, D. kilimanjarica, was found only on Mount Kilimanjaro. This new, highly specific, montane fauna of Drosophila further contributes to the unique biological diversity of the Eastern Arc Mts. The biogeographic affinities of the new taxa suggest past connections with the Virunga and Ruwenzori ranges and further west with the Cameroon Volcanic Line. It indicates, in particular, that the Eastern Arc forests have passed through a succession of coalescence and fragmentation events.

Evidence for altitudinal migration of forest birds between montane Eastern Arc and lowland forests in East Africa

Burgess, N.D. & Mlingwa, C.O.F. 2000. Evidence for altitudinal migration of forest birds between montane Eastern Arc and lowland forests in East Africa. Ostrich 71 (1 & 2): 184–190. In this paper we assess the evidence for altitudinal movements of forest birds from the montane forests of the Eastern Arc mountains of East Africa to nearby lowland forest patches. For 34 montane species, including all the Eastern Arc endemics except Banded Green Sunbird Anthreptes rubritorques there is no evidence that they undertake seasonal movements to lower altitudes. An additional 26 montane species, of somewhat wider distribution, have been recorded at low (<500 m) altitudes during the cold/dry season (June to September). Most records of these montane birds at lower altitudes are from sites adjoining montane forest areas, although a few records are from lowland coastal forests at 100–240 km distance from montane areas. Only five of the 26 species (White-chested Alethe Alethe fulleborni, White-starred Forest Robin Pogonocichla stellata, Orange Ground Thrush Zoothera gurneyi, Evergreen Forest Warbler Bradypterus mariae and Barred Long-tailed Cuckoo Cercococcyx montanus) are regularly and commonly reported in the lowlands. They are also found in the lowlands in small numbers during the warm/wet season (October to February), when they may breed. The abundance of at least four, and probably more, of the forest birds with a more widespread distribution in the lowland and montane forests of East Africa declines greatly at high altitudes from the onset of the cold/wet season (February) and only increases again at the start of the warm/wet season (September). It is not known how far these species move as they cannot be easily separated from resident populations in lowland forests, and there are no ringing recoveries in different forests. Altitudinal migration of a proportion of the Eastern Arc avifauna is the most likely explanation for available data, although source-sink metapopulation theories may be helpful to explain the distributions of some species. As the movement of forest birds from the Eastern Arc to the lowland forests does not involve the rare endemics, they are of lower conservation concern, but the presence of montane and lowland forest may be important for the long-term survival of some more widely distributed forest species.

An Introduction to the Conservation of the Eastern Arc Mountains

It is 19 years ago, that I, as the organiser for the 4th East African Wildlife Symposium, which was hosted in Arusha by the University of Dar es Salaam, dared to add a section on forest biology and forest conservation. The conservation agenda then was concerned with issues of managing elephants and lions and other large hairy wildlife. Conservation then was about National Parks not Forest Reserves, it was about savannah grassland not forests, it was about elephants not camphor trees or African violets. Conservation then still had not got to grips with the involvement of people. Conservation was centred on wilderness areas, not on the people resource interface! Whilst the 1978 conference also had 150 participants from all over the world, few of them cared about forests. It is a sobering thought that today we can host a major conference on the Eastern Arc Forests alone! (Has the world changed? And are we about to see an era of real conservation?). In 1978, most participants were from overseas. In today's workshop, Tanzanians make up over half the active audience! It is instructive to think back 20 years and consider forest conservation issues in Tanzania in 1978: • The word 'conservation' was not in the University Forest Curriculum (not once!). • Forest students did not go to natural forests for training (not once in three years!). Logging and on-farm agro-forestry were the focus topics then. • Intense mechanical logging was underway in the East Usambara Forests, supported by government and foreign aid. • The word biodiversity did not exist. • The human population of Tanzania was half that of today, and the demand for forest products was less than half. Woodland resources were still available to meet much of that fuel wood need. • There were conservation arguments in the Usambara Forests. Much of the canopy had a cardamom understorey. We noted that Kenya with no cardamom growing areas exported twice our national output! • The Forest Department had money and capability-but little conservation concern. But now, there is much greater concern, but lost capacity and no money!

Eastern Tropical African Centre of Endemism: A Candidate for World Heritage Status

ABSTRACT Together with the Coastal Forests and Eastern Arc rainshadow, the Eastern Arc forests make up a botanical Centre of Endemism in Eastern Tropical Africa (CEETA), which covers a wide range of vegetation formations in four different phytochoria. The factors that gave rise to the concentration of restricted-range taxa in the different vegetation types appear to result from the same long-term geological and climatic processes. The endemic-rich vegetation types occur in three countries: Mozambique, Tanzania and Kenya and are managed under a wide range of land tenure arrangements from public land and private ownership, to Forest Reserve, Game Reserve and National Park. Much of the CEETA is recognised as a biodiversity ‘hotspot’ of global importance, but lacks a common management strategy. A possible common framework within which to develop an appropriate strategy is that of the World Heritage Convention. The case of the Australian Wet Tropics World Heritage Site is discussed as a comparative example.

Importance of the Eastern Arc Mountains for Vascular Plants

ABSTRACT The term ‘Eastern Arc’ was introduced in 1985 to describe an exceptionally rich area of restricted range plant species on the crystalline mountains of eastern Tanzania and south-east Kenya. About a third of the Eastern Arc flora is composed of restricted-range species. Qualitative and quantitative data are used to demonstrate that the endemics are spread throughout the elevation and moisture gradients of the Eastern Arc. Because of the high number of endemic plant species, all of the Eastern Arc forests are of importance to conservation. However, ridge-tops, heaths, limestone forests and dry forest types are vegetation formations occupying a small area and so are conservation priorities.

Assessment of the impact of the Lower Kihansi Hydropower Project on the forests of Kihansi Gorge, Tanzania

Construction of a hydropower project on the Kihansi river in Southern Tanzania will substantially alter the river's flow. On the basis of both qualitative and quantitative botanical surveys, forest in the Kihansi gorge below the dam site was found to be mostly typical species and endemic-rich Eastern Arc forest. An unusual forest type, dominated almost entirely by Filicium decipiens was also present. Eastern Arc forests are of both global and national importance for biodiversity conservation, and measures to mitigate impact of the dam on the forest are suggested. Further environmental monitoring is recommended in order to evaluate the choice of mitigation measures.