Assisting natural forest regeneration in Northern Ethiopia: one measure is not enough

Management strategies aimed at rehabilitating degraded and cleared forests often rely on temporary or permanent exclusion of herbivores (wild animals, livestock or both). But in many cases, this simple management technique is not sufficient to induce ecosystem restoration: many negative effects keep the ecosystem in a suboptimal, low biomass state. The presence of such stable states requires restoration measures to act on multiple stress factors simultaneously.

Compensating for all limiting factors is neither practically nor economically feasible. But detailed knowledge about the autoecology of tree species – i.e. their site requirements, regeneration strategies and recruitment dynamics – may be used to tailor management to the most pertinent problems. Here we illustrate this approach with results from forest restoration experiments in grazing exclosures in northern Ethiopia using African wild olive (_Olea europaea_ ssp. _cuspidata_) as a representative Afromontane climax species.

The recruitment of African wild olive is affected by seed limitation, restricted seed dispersal and germination and survival limitation. The exclusion of grazing animals as a single measure to restore forest is not enough. Degraded grazing land moves into a state dominated by persistent shrubs, arresting forest succession and discouraging local stakeholders. Direct sowing or planting of seedlings in fertile patches under selected pioneer shrubs, however, may help to overcome this form of bush encroachment, in particular during years with an above-average rainfall.
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Historical deforestation patterns and the conservation value of church forests in the northern Ethiopian highlands

Mountain forest plants have a limited capacity for migration because altitudinal gradients usually set strict limits to plant species’ ranges and often present physical barriers against dispersal. Innate ‘islands’ of biodiversity, mountain forests are therefore particularly vulnerable to the effects of climatic change and habitat fragmentation, both key drivers of global species loss. Conservation of these ecosystems must for that reason rely on protecting not only large fragments but also small habitat patches and relictual vegetation along a wide altitudinal range.
When large fragments in such ecosystems are no longer available, small fragments become an environmental priority. Striking examples of small mountain forest fragments are the church forests of the northern Ethiopian highlands. In a landscape dominated by degraded semiarid savanna, sacred groves represent the majority of all remaining patches of Afromontane forest. Previous studies in the region only covered few fragments and could not adequately estimate the conservation value of these forests. For that reason, we digitized 394 church forests in an area of half a million hectares by systematically scanning high spatial resolution satellite images (pixel resolution 0.8 m) in eight blocks in the northern highlands and calculated area, density, shape, isolation and configuration metrics. Forest cover is only 0.2%, much lower than usually estimated in the literature (4%). Fragment shape and spatial configuration in the north and northeast of the surveyed area (irregular forests on northwestern slopes with churches near the forest edge) are consistent with forest conservation after fragmentation, while forests in the south and west (regular round forests surrounding a central church) indicate conservation prior to widespread deforestation. Fragments are small throughout the region (2.5 +- 0.2 ha) and need expansion, but known vegetation differences between church forests related to the two different historical fragmentation processes call for different strategies for forest conservation and restoration.
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The Dallol Volcano

The Dallol Volcano (14°14’13" N 40°17’53" E, 85m below sea level) is an explosion crater in the Danakil Depression in northern Ethiopia and is located in one of the hottest and most remote places on Earth. Surrounded by vast salt and sulphur plains and featuring geysers, puddles of boiling mud and bright acidic pools, the crater has become an important eco-tourism attraction of the Afar regional state. Exposure to extreme temperatures and the ceaseless wind, which the local Afar nomads call hahaita-harrur or fire-wind, triggers dehydration, high sweat salt losses and heat stress. Heat injuries and hyponatremia are potentially life-threatening in this hostile environment. On overnight stays in the Danakil, we used evaporation pans to chill our drinking water and oral rehydration salt to prevent dilutional hyponatremia. Photograph by Raf Aerts, MSc, PhDWilderness Imagestatus: publishe

Birds of forests and open woodlands in the highlands of Dogu’a Tembien

The landscape in Dogu’a Tembien, in the northern highlands of Ethiopia, is a mosaic of cropland, woodland and evergreen scrub with isolated patches of dry forest. Ethiopia is endowed with an exceptionally rich fauna and flora, and is a global hotspot of biodiversity and endemicity. In Ethiopia and Eritrea, 872 bird species occur, representing 39% of the bird species of Africa and including 32 endemic species. Likewise, the forest-woodland-grassland complex in Dogu’a Tembien is the habitat of a rich and interesting yet relatively underexplored bird fauna with several endemic and biome-restricted species. In this chapter, we will look at birds in forest fragments and open woodland of varying ecological quality, in particular church forests, grazing exclosures and grazed woodland. We demonstrate that birds contribute substantially to the cultural ecosystem services of the landscape by providing a high ecotourism potential.status: publishe

Improvised Hand Injury Treatment Using Traditional Veterinary Medicine in Ethiopia

In remote wilderness environments, local people with traditional knowledge of medicinal plants are potentially important first-line health care providers. We present a case of a 31-year-old man who fell off a horse while trekking through a remote mountain landscape in Ethiopia and sustained blunt force trauma to the hand. A local mountain hut keeper examined the patient’s hand and used heated leaves of the succulent plant Kalanchoe petitiana to treat a suspected metacarpal fracture. As first responder in a low-resource setting, the hut keeper relied on his traditional knowledge of ethnoveterinary medicine to improvise a treatment for a human injury in a remote mountain environment. Although in this case the outcome of the traditional intervention was positive, our analysis shows that the massage component of the intervention could have led to complications. Conversely, reports from the use of related Kalanchoe species suggest that heated Kalanchoe leaves could be useful in the compression component of traditional care for hand injuries. Validation of traditional remedies and their therapeutic potential are needed if they are to complement wilderness wound care safely and reliably. The documentation and validation of these remedies are urgently needed, as many medicinal plants and indigenous knowledge of how to use these valuable natural resources are being lost.status: publishe

Recruitment dynamics of African wild olive (Olea europeae subsp. cuspidata): some observations from Central-Tigray and their implications for natural forest regeneration

The ability of rehabilitation areas to recruit and sustain new life forms is a true measure of their contribution to biodiversity and forest resource conservation. In Africa, relatively few studies have evaluated the effect of early colonizing shrubs on seed dispersal, seed and seedling predation and competition and their consequences for woody seedling establishment. Shrubs might facilitate, tolerate or inhibit different stages of tree establishment in abandoned pastures or croplands. Seed dispersal, post-dispersal predation, germination and recruitment of a late successional tree species, African wild olive (Olea europaea subsp. africana; Oleaceae), were examined in closed and non-closed areas in the Geba river catchment of Central-Tigray. The following hypothesis was tested experimentally: recruitment of O. europaea will be higher under certain early colonizing shrubs as compared to gaps and other shrubs. Despite the expected higher seed predation and competition under these natural structures, some shrub clusters are believed to create microhabitats that enhance seedling survival by decreasing the risk of desiccation and predation by livestock and wild animals. Both in rangeland and closed areas, recent recruitment of O. europaea was predominantly found under Euclea schimperi shrubs, although Acacia bushes were more numerous. Preliminary results suggest that structural traits cause this disparity. In rangeland, the limiting factor for Olea recruitment is believed to be grazing pressure rather than seed input. Natural structures that act as a preferential perching site for frugivorous birds and that offer adequate protection at ground level are the key recruitment foci. In closed areas, high competition by abundant grasses and herbs restricts seedling establishment. Moreover, dense ground cover and the presence of physical soil conservation structures (stone bunds) increase post-dispersal seed predation. Formation of new shoots from old rootstocks, however, can ensure Olea woodland regeneration, provided that a sufficient amount of old rootstocks persists in the protected area. All this suggests that the application of appropriate protection and silvicultural measures can significantly enhance natural regeneration of indigenous woodlands in the region without having to rely on expensive plantation activities.status: publishe

Conservation of the Ethiopian church forests : Threats, opportunities and implications for their management

In the central and northern highlands of Ethiopia, native forest and forest biodiversity is almost confined to sacred groves associated with churches. Local communities rely on these 'church forests' for essential ecosystem services including shade and fresh water but little is known about their region-wide distribution and conservation value. We (1) performed the first large-scale spatially-explicit assessment of church forests, combining remote-sensing and field data, to assess the number of forests, their size, shape, isolation and woody plant species composition, (2) determined their plant communities and related these to environmental variables and potential natural vegetation, (3) identified the main challenges to biodiversity conservation in view of plant population dynamics and anthropogenic disturbances, and (4) present guidelines for management and policy. The 394 forests identified in satellite images were on average ~ 2 ha in size and generally separated by ~ 2 km from the nearest neighboring forest. Shape complexity, not size, decreased from the northern to the central highlands. Overall, 148 indigenous tree, shrub and liana species were recorded across the 78 surveyed forests. Patch α-diversity increased with mean annual precipitation, but typically only 25 woody species occurred per patch. The combined results showed that >. 50% of tree species present in tropical northeast Africa were still present in the 78 studied church forests, even though individual forests were small and relatively species-poor. Tree species composition of church forests varied with elevation and precipitation, and resembled the potential natural vegetation. With a wide distribution over the landscape, these church forests have high conservation value. However, long-term conservation of biodiversity of individual patches and evolutionary potential of species may be threatened by isolation, small sizes of tree species populations and disturbance, especially when considering climate change. Forest management interventions are essential and should be supported by environmental education and other forms of public engagement.</p

Land rehabilitation and the conservation of birds in a degraded Afromontane landscape in northern Ethiopia

The few remaining Afromontane forest fragments in northern Ethiopia and the surrounding degraded, semiarid matrix form a habitat mosaic of varying suitability for forest birds. To evaluate the effect of recent land rehabilitation efforts on bird community composition and diversity, we studied bird species distributions in ten small forest fragments (0.40–20.95 ha), five grazing exclosures (ten-year-old forest restoration areas without wood extraction and grazing livestock) and three grazed matrix sites during the rainy season (July-October 2004) using 277 one-hour species counts. Based on the distribution pattern of 146 bird species, sites were assigned to one of three bird communities (birds of moist forest, dry forest or degraded savanna), each occupying a well-defined position along an environmental gradient reflecting decreasing vegetation structure and density. All three communities were representative of the avifauna of Afrotropical Highland open forest and woodland with a high proportion of invasive and competitive generalist species (31%). Apart from these, exclosures shared more species with forest fragments (20%) than did the grazed matrix (5%), indicating local ecosystem recovery. By increasing habitat heterogeneity, exclosures have the potential to enhance landscape connectivity for forest birds and are, therefore, an effective instrument for conserving species in a fragmented landscape. However, 52 bird species (36%) occurred exclusively within forest patches and many forest birds that use exclosures are unlikely to maintain viable populations when forest fragments disappear, particularly as forest fragments may be a critical resource during the hot dry season. This highlights the high conservation value of small isolated forest fragments for less tolerant, forest-limited and/or biome-restricted species.status: publishe