SW Ethiopia Research Articles

Magma‐Assisted Continental Rifting: The Broadly Rifted Zone in SW Ethiopia, East Africa

AbstractThe Gofa Province and Chew Bahir Basin in the Broadly Rifted Zone (BRZ) between the southern Main Ethiopian Rift (sMER) and the northern Kenya Rift (nKR) record early volcanism and associated faulting in East Africa; however, the spatiotemporal relationships between volcanism and faulting remain poorly constrained. We applied apatite (U‐Th)/He (AHe) and zircon (U‐Th)/He (ZHe) thermochronometry to Neoproterozoic basement rocks from exhumed footwall blocks of the extensional Gofa Province and Chew Bahir Basin, and analyzed our result in the context of well‐dated regional volcanic units in the BRZ to unravel the interplay between tectonic exhumation, faulting and volcanism. Single‐grain AHe ages ranging from 1.0 to 136.8 Ma were recorded in 32 samples, and single‐grain ZHe ages from three samples range between 142.2 and 335.6 Ma. The youngest AHe ages were obtained from the Chew Bahir Basin and the narrow deformation zone in the Gofa Province. Our thermal modeling results reflect little or no significant regional crustal cooling prior to extensive volcanism, which started at about 45 Ma. Conversely, new and previously published thermal history models suggest that widespread crustal cooling related to regional extension occurred between ∼27 and 20 Ma. Thermal modeling results from subsets of samples indicate that following this initial diffuse extensional deformation, renewed exhumation occurred along a narrow zone within the Gofa Province and the Chew Bahir Basin during the middle to late Miocene (15‐6 Ma) and Pliocene (<5 Ma), respectively. The crustal cooling phases follow a regional trend in volcanic episodes. For example, initial cooling between 27 and 20 Ma corresponds with the end of widespread flood‐basalt volcanism (45–28 Ma), suggesting that spatially diffuse normal faulting may have initiated shortly after the emplacement of voluminous and areally extensive flood basalts. The Miocene and Pliocene shifts in deformation along the Mali‐Dancha and Bala‐Kela basins in the Gofa Province and the Chew Bahir Basin, respectively, may indicate strain localization during the late stage of rifting and ongoing tectonic interaction between the sMER and the nKR. Our results support the notion of crustal weakening by massive volcanism as a precursor to widespread extensional faulting, and thus offer further insights into magma‐assisted deformation processes in the East African Rift System.

Topographic amplification of seismic ground motion at the broad rift zone of SW Ethiopia

Topographic amplification of seismic ground motion at the broad rift zone of SW Ethiopia

40 Ar/ 39 Ar eruption ages of Turkana Basin tuffs: millennial-scale resolution constrains palaeoclimate proxy tuning models and hominin fossil ages

The Turkana Basin in NW Kenya and SW Ethiopia hosts remarkable fossil-rich sediments that are central to our understanding of early hominin evolution, with interbedded volcanic tuffs providing critical time markers. However, the resolution of existing Early Pleistocene–Pliocene ages is limited to c. 20–60 kyr, inhibiting the evaluation of climatic and environmental drivers of evolution. We present high-precision, single-feldspar 40 Ar/ 39 Ar age and elemental data for four stratigraphically significant tuffs. These samples exhibit variably dispersed age distributions correlated with feldspar compositional trends, interpreted to indicate the partial retention of inherited 40 Ar related to crustal ‘cold storage’ and rapid melt infiltration preceding eruption. We evaluated various statistical methods and calculated astronomically calibrated Bayesian age estimates of 1879.1 ± 0.6 ka (±2.4 ka including external errors) for the Kay Behrensmeyer Site (KBS)/H2 Tuff, 1837.4 ± 0.9 ka (±2.4 ka) for the Malbe/H4 Tuff, 1357.5 ± 1.8 ka (±2.5 ka) for the Chari/L Tuff and 1315.4 ± 1.9 ka (±2.5 ka) for the Gele Tuff. Our results permit refined age constraints for important early Homo fossils, including the cranium KNM-ER1813 ( Homo habilis ) and various Homo erectus fossils. The KBS Tuff age also provides an important calibration locus for orbital tuning of palaeoclimate proxy records, revealing the complex interplays between palaeoclimate and geological drivers of sedimentation. Supplementary material : The supplementary tables and figures include previously published ages (Table S1), sample and irradiation information (Table S2), electron probe microanalytical results for tuff glasses (Table S3, Figs S2 and S3) and feldspars (Table S4), 40 Ar/ 39 Ar analytical data (Tables S5 and S6, Fig. S4), orbital tuning model parameters (Table S7), a summary of previous and revised hominin ages (Table S8) and a worked Bayesian estimation example (Fig. S1) and are available at https://doi.org/10.6084/m9.figshare.c.6602994

Land use land cover change in and around Chebera Churchura National Park, Southwestern Ethiopia: implications for management effectiveness

BackgroundLand use-land cover change (LULCC) resulting from anthropogenic activities has been one of the major causes of loss of biodiversity globally. Thus, understanding the dynamics of such LULCC, especially within protected areas, is important to assess their past-present management effectiveness, identify the driving forces and assist future implementation of mitigation measures. The objectives of this study, based on satellite images analysis, were to examine and describe patterns of LULCC within and in the buffer zone area of Chebera Churchura National Park, SW Ethiopia, at five points in time (1985, 1991, 2000, 2010, and 2020); and to examine management effectiveness of the park authority in slowing down the rate of LULCCs after the establishment of the park.ResultsResults showed that different land cover types exhibited varying patterns of change over the last 35 years. However, major differences were detected between the park area boundary and its buffer zone area after establishment of the park. From the year 1991 to 2000 (before the establishment), grassland declined by 52.9% (120.55km2) and 58.9% (151.9km2) within the park boundary and its buffer zone, respectively. After the establishment, grassland continued to decline only in the buffer zone. Similarly, agricultural land declined by 13.2% (2.7 km2) within the park but expanded by 5.4% (3.1 km2) in the buffer zone prior to park establishment. However, after establishment of the park, agricultural land in the buffer zone increased by 99.4% (99.7 km2). Grassland and wooded grassland had the opposite trend within the park area before vs after the establishment of the park.ConclusionsResults of the present study showed that striking differences in the rates of LULCCs within the park area and its buffer zone after establishment of the park, with the implication that the management is effective in slowing down LULCC relative to that in the buffer zone areas. In sum, this study would serve as a showcase on cost-effective means to assess human impacts on biodiversity in protected areas due to policy changes. Findings of the study would serve as a bench mark to evaluate future management effectives of the park authority.

Composition and structure of woody plant communities as a function of altitude and human degradation in Afromontane moist evergreen forests SW Ethiopia

AbstractTropical moist evergreen forests provide key ecosystem services for human well‐being. However, due to human pressure, Afromontane forests have lost much of their natural species composition and structure. In this study, vegetation surveys were carried out with the aim of investigating woody species composition and structure and their drivers of degradation in SW Ethiopia. Woody plant species were identified, forest structure measured and environmental variables determined in 75 plots across four forest patches along an altitudinal gradient. The result shows that the remaining patches still have 63 woody species from 36 families. Our results showed the presence of three plant communities: a first mid‐elevation degraded mountain forest community, a second mid‐elevation more intact community and a third higher elevation degraded cloud forest community. The Shannon diversity index of the second community was significantly higher than the first and the third community. Exotic tree planting and charcoal production were important determinants of the first community composition. Despite their socioecological importance, the expansion of exotic tree planting showed to be a major threat for natural forest ecosystem. In the study area, intervention is needed to maintain the ecological balance between plantation and natural forest.

A Multi-Method Approach for Deciphering Rockshelter Microstratigraphies—The Role of the Sodicho Rockshelter (SW Ethiopia) as a Geoarchaeological Archive

The Sodicho Rockshelter in the southwestern Ethiopian Highlands presents a unique site that contains sediments of Upper Pleistocene and Holocene occupation phases of hunter-gatherer communities. Excavations and previous geoarchaeological research provided a first 14C chronostratigraphic framework for the last 27 ka cal BP, which supports the hypothesis of a potential environmental refugium during the Late Glacial Maximum (LGM, ~21 ± 2 ka). Nonetheless, it is necessary to extend the preliminary interpretation of stone tool assemblages, and the geoarchaeological analyses carried out so far to provide in-depth information on prehistoric human behavior at the site under changing climatic and environmental conditions. In this study, we reinvestigate the complex stratigraphy and the paleoclimatic context of Sodicho in order to expand the knowledge about site formation, post-depositional disturbances, weathering influences, and the anthropogenic impact on the sediment deposits. Micromorphological observations and the determination of active pedogenic oxides offered a more detailed look at the microstratigraphic record in relation to shifting moisture conditions during the African Humid Period (AHP, ~15 − 5 ka). Sediment alteration and reworking are connected to the influence of sheet flow, biological activity, and human impacts such as dumping activity and site maintenance. A comparison with black carbon (BC) analyses and a qualitative phytolith ratio (quantification of dark and light phytoliths) provided evidence for variations in human fire intensity. Our collaborative and multidisciplinary approach demonstrates how the complex formation of a rockshelter site in a tropical setting with changing climatic and anthropogenic impacts can be tackled.

Initial Cenozoic magmatic activity in East Africa: new geochemical constraints on magma distribution within the Eocene continental flood basalt province

Abstract The initial interaction between material rising from the African Large Low Shear Velocity Province and the African lithosphere manifests as the Eocene continental large igneous province (LIP), centred on southern Ethiopia and northern Kenya. Here we present a geographically well-distributed geochemical dataset comprising flood basalt lavas of the Eocene continental LIP to refine the regional volcano-stratigraphy into three distinct magmatic units: (1) the highly alkaline small-volume Akobo Basalt (49.4–46.6 Ma), representing the initial phase of flood basalt volcanism derived from the melting of lithospheric–mantle metasomes; (2) the primitive and spatially restricted Amaro Basalt (45.2–39.8 Ma), representing the early main phase of flood basalt volcanism derived from the melting of the upwelling thermochemical anomaly; and (3) the spatially extensive Gamo–Makonnen magmatic unit (38–28 Ma), representing the mature main phase of flood basalt volcanism that has undergone significant processing within the lithosphere and resulted in relatively homogeneous compositions. The focused intrusion of these main phase magmas over 10 myr preconditioned the African lithosphere for the localization of strain during subsequent episodes of lithospheric stretching. The focusing of strain into the region occupied by this continental LIP may have contributed to the initial extension in SW Ethiopia that is associated with the East African Rift.

Singing the Individual: Name Tunes in Oyda and Yopno.

Music beats spoken language in identifying individuals uniquely in two disparate communities. In addition to their given names, which conform to the conventions of their languages, speakers of the Oyda (Omotic; SW Ethiopia) and Yopno (Finisterre-Huon; NE Papua New Guinea) languages have “name tunes,” short 1–4 s melodies that can be sung or whistled to hail or to identify for other purposes. Linguistic given names, for both communities, are often non-unique: people may be named after ancestors or contemporaries, or bear given names common to multiple individuals. But for both communities, name tunes are generally non-compositional and unique to individuals. This means that each new generation is likely to bring thousands of new name tunes into existence. In both communities, name tunes are produced in a range of contexts, from quotidian summoning and mid-range communication, to ceremonial occasions. In their use of melodies to directly represent individual people, the Oyda and Yopno name tune systems differ from surrogate speech systems elsewhere that either: (a) mimic linguistic forms, or (b) use music to represent a relatively small set of messages. Also, unlike some other musical surrogate speech traditions, the Oyda and Yopno name tune systems continue to be used productively, despite societal changes that have led to declining use in some domains.

Influence of location, elevation gradients, processing methods, and soil quality on the physical and cup quality of coffee in the Kafa Biosphere Reserve of SW Ethiopia

In-depth forest coffee cup quality assessments have not been conducted yet on Kafa Biosphere Reserve coffees. Hence, the influence of location, elevation gradient, and processing methods on coffee bean physical and sensorial qualities, and the relationship between soil and coffee quality variables were studied in 2017. Districts (Gimbo, Gawata, and Decha), elevation gradient ranges (low-<1600, mid-1600-1800, and high->1800 m a.s.l), and processing methods (wet, semi-wet, and dry) were taken as factors. Preliminary coffee quality assessment data was collected from cup quality analysis of coffee beans obtained from the combination of the three factors where four replicate samples were taken for each of the combinations. The effect of location was only significant for bean moisture content and there was no significant (P > 0.05) difference among locations for above 14 screen retention and preliminary cup quality variables (odor, raw, acidity, body, flavor, cup, total, and grade). The elevation gradient had a significant (P < 0.001) effect on the scores of above 14 screen retention and most of the cup quality variables, but not on moisture content and odor. The effect of the coffee processing method was not significant (P > 0.05) on most of the preliminary cup quality variables, but it was significant for moisture content (P < 0.001), odor (P < 0.05), and overall raw (P < 0.01) scores. Screen retention was decreased with increasing elevation gradient but with better quality. High elevation coffees processed with the dry method gave better raw (38.5–40 ​%) and cup (48.00–51.75 ​%) quality scores. Except for high soil molybdenum and clay percentage, reduced amounts of most of the soil nutrients, pH, and silt percentage were important for better forest coffee quality. Since each sampled forest had diverse shade types and densities, a further investigation that includes the component of shade is strongly recommended in future studies.

Soil and water conservation management on hill slopes in southwest Ethiopia. II. Modeling effects of soil bunds on surface runoff and maize yield using AquaCrop

On the cultivated slopes of the highlands of southwest Ethiopia, soil degradation due to water erosion is a challenge for crop production. To limit surface runoff and soil erosion, soil bunds often in combination with trenches, constructed along contour lines, are common. In addition to the interception of surface runoff, soil bunds may affect crop yield. Here, we evaluate effect of soil bunds on surface runoff and maize yield, using FAO's AquaCrop model, calibrated based on field experiments in the Bokole-Karetha watershed, in SW Ethiopia. Experiments were conducted in 2018 and 2019 on three neighboring fields, each comprising plots in triplicate without and with soil bunds. Experimental data from 2018 to 2019, which were average and above average with respect to rainfall, indicate that water availability was sufficient or even in excess for maize production. Soil bunds significantly (p < 0.05) reduced surface runoff, but maize yield did not differ significantly. In plots without soil bunds, the AquaCrop model described surface runoff satisfactorily after slight adjustment of the curve number (related to infiltration capacity) in one of the three fields. Maize yields were reproduced adequately after calibrating soil fertility and adjusting water productivity. After calibration and validation, the AquaCrop model was used to hindcast surface runoff and grain yield from 1999 to 2017, given available climatic data for the region. Hindcasts show that maize yield in the Bokole-Karetha watershed, with its relatively high rainfall, is not significantly affected by rainfall in two of the three fields. In the third field maize yield decreases slightly, but significantly (p < 0.05) with rainfall. In the short run, yield differences between plots with and without soil bunds are not significant. However, eventually high surface runoff from plots without soil bunds are expected to result in unsustainable crop production, due to significant erosion and degradation of the often nutrient-poor soils. Implementation of soil and water management techniques, combined with fertilization, are important to prevent soil degradation and nutrient stress on sloping land.

Determinants of farm livelihoods of smallholder farmers in Yayu biosphere reserve, SW Ethiopia: a gender disaggregated analysis

Improving food security has remained to be one of the major challenges in Sub-Saharan Africa, where Ethiopia is not an exception. As a result of poor productivity of the farming sector, smallholder...

Essential oil yield and yield components of basil (Ocimum basilicum L.) as affected by genotype and intrarow spacing at Jimma, SW Ethiopia

Basil is an aromatic, medicinal, culinary, and multifunctional herb which is grown in different parts of Ethiopia. Although the oil distilled from the herb, as well as its herbal yields, are a crucial input in the pharmaceutical industry and for culinary purposes, the yield obtained is below its potential due to various challenges. Genotype and plant spacing are two of the factors which contribute to the low production of the crop. A field trial was conducted at Jimma University College of Agriculture and Veterinary Medicine (JUCAVM) in 2016 and 2017 to assess the effect of genotype and plant spacing on essential oil yield and other yield-related traits of this important herb. Four promising genotypes (BO-1, BO-3, BO-4, and BO-5) and three plant spacings (20, 30, and 40 cm) were studied in a 4 × 3 factorial design arranged as randomized complete blocks (RCBD) with three replications. Data on plant height, leaf area, number of primary branches, essential oil content and oil yield were collected and analyzed. The analysis of variance revealed that there were highly significant (&lt;em&gt;p&lt;/em&gt; &amp;lt; 0.01) interaction effect of genotype with plant spacing for all parameters tested. The maximum essential oil yield (7.88 kg ha&lt;sup&gt;−1&lt;/sup&gt;) was obtained from genotype BO-5 at 30 cm spacing, whilst the least (2.68 kg ha&lt;sup&gt;−1&lt;/sup&gt;) was recorded from BO-1 at 40 cm spacing. The maximum oil content (101 mL g&lt;sup&gt;−1&lt;/sup&gt;) was gained from BO-1 at 20 cm, but BO-3 at 30 cm spacing recorded the least oil content though there were no significant differences between the three treatment combinations. Further studies at different locations and seasons will be important to for future local recommendations.

Intensification of Ethiopian coffee agroforestry drives impoverishment of the Arabica coffee flower visiting bee and fly communities

Intensively managed shade coffee plantations are expanding in SW Ethiopia, at the cost of the more natural coffee agroforestry systems. Here, we investigated consequences for the potential pollinator community of Arabica coffee (Coffea arabica L.) in its natural range. We surveyed coffee flower visitors at six different sites in the Jimma region in SW Ethiopia, and compared species richness and abundance between semi-natural coffee forests and shaded coffee plantations. Overall, we found six bee (Hymenoptera: Anthophila) and twenty fly species (Diptera: Brachycera) visiting C. arabica flowers. Species richness and overall abundance of flower visitors was significantly higher in the semi-natural forests compared to the plantations. A significantly higher abundance of non-Apis bees and hoverflies (Syrphidae) visiting C. arabica flowers was observed in the semi-natural forest plots, but numbers for other Diptera and honeybees (Apis mellifera L.) did not differ significantly between the agroforestry systems. Our results show an impoverishment of the coffee flower visiting insect community in response to agricultural intensification. This suggests a functional shift of the coffee pollinator community and, hence, may influence the stability of the provided pollination ecosystem services and coffee yield in the long term. We did, however, not quantify pollination services in this study.

African Forest Honey: an Overlooked NTFP with Potential to Support Livelihoods and Forests

In parts of the developing world, deforestation rates are high and poverty is chronic and pervasive. Addressing these issues through the commercialization of non-timber forest products (NTFPs) has been widely researched, tested, and discussed. While the evidence is inconclusive, there is growing understanding of what works and why, and this paper examines the acknowledged success and failure factors. African forest honey has been relatively overlooked as an NTFP, an oversight this paper addresses. Drawing on evidence from a long-established forest conservation, livelihoods, and trade development initiative in SW Ethiopia, forest honey is benchmarked against accepted success and failure factors and is found to be a near-perfect NTFP. The criteria are primarily focused on livelihood impacts and consequently this paper makes recommendations for additional criteria directly related to forest maintenance.

Assessment of berry drop due to coffee berry disease and non-CBD factors in Arabica coffee under farmers fields of Southwestern Ethiopia

To evaluate the effective impact of Coffee Berry Disease (CBD) on berry loss in the smallholder context of SW Ethiopia, CBD symptoms were monitored during the rainy seasons of two consecutive years on both protected (with fungicide applications) and unprotected coffee branches. Fungicide applications (mancozeb) had significant effect (P < 4e-05) on the proportion of necrotic and dropped berries; CBD necrotic symptom was reduced from 48.7% (non treated) to zero (treated) while berry drop was reduced from 52.8% (non treated) to 40.8% (treated), suggesting that only 12.1% of the observed berry loss could certainly be attributed to CBD. Disease incidence was not influenced by the branch position in the canopy of the monitored trees. Altitude was an important factor controlling the disease incidence as it favored the development of both necrotic and drop symptoms. The result suggests that non-CBD factors controlling the physiology of berry production, such as plant age, pruning or soil fertilization, climate are predominant in the studied context to explain yield loss, and that berry drop symptom assessment alone may lead to an overestimation of CBD impact.

Conserving wild Arabica coffee: Emerging threats and opportunities

Climate change and emerging pests and diseases are posing important challenges to global crop productivity, including that of Arabica coffee. The genetic basis of commercially used Arabica coffee cultivars is extremely narrow, and it is uncertain how much genetic diversity is present in ex situ collections. Conserving the wild Arabica coffee gene pool and its evolutionary potential present in the montane forests of SW Ethiopia is thus critically important for maintaining coffee yield and yield stability worldwide. Globally, coffee agroforestry helps to conserve forest cover and forest biodiversity that cannot persist in open agricultural landscapes, but the conservation of the wild Arabica coffee gene pool requires other priorities than those that are usually set for conserving forest biodiversity in mixed tropical landscapes. We show how forest loss and degradation, coffee management, in particular production intensification, and the introduction of cultivars, are threatening the genetic integrity of these wild populations. We propose an active land sparing approach based on strict land use zoning to conserve the genetic resources and the in situ evolutionary potential of Arabica coffee and discuss the major challenges including the development of access and benefit sharing mechanisms for ensuring long-term support to conservation.

A new MIS 3 radiocarbon chronology for Mochena Borago Rockshelter, SW Ethiopia: Implications for the interpretation of Late Pleistocene chronostratigraphy and human behavior

With excavated layers spanning a period from >49ka to ~36ka, Mochena Borago Rockshelter reveals a complex sequence of Late Pleistocene human occupation punctuated by volcanic events. Fifty-nine radiocarbon ages make Mochena Borago one of the best-dated Late Pleistocene archaeological sites in eastern and northeastern Africa. However, complex site formation processes, dramatic stratigraphic differences between non-contiguous excavation areas, and “outlier” dates that appear in various parts of Mochena Borago's sequence, complicate efforts to develop a secure and detailed chronology for local and regional behavioral changes. This article focuses on contiguous squares within the Block Excavation Area (BXA) trench at the northern end of the shelter. Bayesian modeling of thirty-seven dates from six major lithostratigraphic units within the BXA yields a revised series of age ranges; these differ from the previous age model (derived from weighted means) in subtle but important ways. Perspectives gained through Bayesian analysis stimulate more careful consideration of the complex site formation processes operating at Mochena Borago, the contextual integrity of the site's robust and distinctive flaked stone artifact assemblages (lithics), and potential correlations between lithic changes and environmental events that occur on local, regional, and global scales. As these factors come into focus, Mochena Borago can serve as an important chronological benchmark to better understand human behavior in eastern and northeastern Africa around the time of the second major dispersal of Homo sapiens.

Response of upland rice ‘Nerica-4 ’to rates of N and P fertilizers in south west Ethiopia

Decline in soil fertility is a major constraint in Abol Woreda of Gambella region of SW Ethiopia due to the continuous cropping, removal of crop residues after harvest, poor application of organic manures to soils, etc. The scientific information available concerning the response of upland ‘Nerica-4 ’rice variety to rates of N and P fertilizers in Gambella for its optimum productivity is limited. Therefore, a field experiment was carried out during 2014 cropping season at Abol Woreda, Gambella, South West Ethiopia to investigate optimum rates of N and P fertilizers for highest yield of rice (Oryza sativa L.). The treatments consisted of factorial combinations of four rates of N (0, 46, 92, and 138 kg N ha−1) and P (0, 23, 46, and 69 kg P ha −1) was laid out in a randomized complete block design (RCBD) with three replications. The effects of nitrogen were significantly (P = 0.05) different for harvest index, 1000-grain weight, plant height, panicle length, grain yield, straw yield, number of filled spikelets and unfilled spikelets, productive tillers, number of tillers and dry grain weight. On the other hand, many growth, yield, and yield components did not differ significantly (P > 0.05) due to application of P except number of unfilled spikelets, straw yield, and grain yield. Conversely, the interaction of N and P was significant (P = 0.01) for all yield and yield components except straw yield, harvest index and panicle length. Application of N and P significantly (P = 0.01) increased grain yield of rice up to the level of 92 kg N and 69 kg P ha−1. Highest grain yield (6.05 t ha−1) was obtained with the combined application of 92 kg N ha−1 and 69 kg P ha−1, and the yield advantage over the control was 113.7% (3.22 t ha−1). The economic analysis revealed that 92 kg N ha−1 with all rates of P (0, 23 and 46 kg) gave highest net benefits. Grain yield was significantly and positively correlated with straw yield (r = 0.66**), productive tillers (r = 0.423**), plant height (r = 0.632**), grain weight (r = 0.54**), panicle length (r = 0.453**), number of spikelets panicle−1 (r = 0.441**) and number of filled grain (r = 0.362**). This indicates that N and P increase grain yield of rice by positively affecting the important yield components. Therefore, it is inferred that farmers in the region can apply 92 kg N ha−1 with no phosphorus application to improve the grain yield of rain-fed Nerica-4 rice as well as for highest economic benefit.

Management intensification in Ethiopian coffee forests is associated with crown habitat contraction and loss of specialized epiphytic orchid species

The moist evergreen Afromontane forest of SW Ethiopia has become extremely fragmented and most remnants are intensively managed for cultivation of coffee (Coffea arabica). We investigated the distributions of epiphytic orchids in shade trees and their understory in forests with contrasting management intensity to determine biodiversity losses associated with coffee cultivation and to determine the capacity of coffee shrubs to act as refugia for orchid species. We studied epiphytic orchids in managed forests and natural forests and recorded orchid diversity and abundance in different tree zones of 339 trees and in the understory. Coffee management was associated with a downward shift of orchid species as orchid species were occurring in significantly lower tree zones in managed forest. The number of shrubs in the understory of managed forest was not higher than in natural forests, yet orchid abundance was higher in the understory of managed forests. Local extinctions of epiphytic orchids and species losses in the outer tree zones (a contraction of habitat) in managed forests are most likely driven by losses of large, complex-structured climax trees, and changes in microclimate, respectively. Coffee shrubs and their shade trees in managed forests are shown here to be a suitable habitat for only a limited set of orchid species. As farmers continue to convert natural forest into managed forest for coffee cultivation, further losses of habitat quality and collateral declines in regional epiphytic orchid diversity can be expected. Therefore, the conservation of epiphytic orchid diversity, as well as other components of diversity of the coffee forests, must primarily rely on avoiding coffee management intensification in the remaining natural forest. Convincing farmers to keep forest-climax trees in their coffee forest and to tolerate orchids on their coffee shrubs may also contribute to a more favorable conservation status of orchids in Ethiopian coffee agroecosystems.

REALU vs. REDD+: Carbon and biodiversity in the Afromontane landscapes of SW Ethiopia

A major constraint to current REDD+ initiatives is the arbitrariness of the operational definition of ‘forest’. The UN-REDD+ framework ignores the high potential of other (tree containing) land uses for carbon sequestration and the generation of co-benefits, in contrast to a whole landscape approach known as ‘Reducing Emissions from All Land Uses’ (REALU). To indicate this potential, carbon stocks and biodiversity were assessed at the landscape scale around Jimma, SW Ethiopia. Notwithstanding the indigenous forests’ high carbon stocks per hectare (336.96±120.6MgCha−1), 80% of the total carbon stock of the 106ha assessed landscape window was found to be stored in non-forest land uses. Especially local agroforestry systems, such as managed semi-forest coffee production fragments (179.92±38.5MgCha−1), homegardens (106.26±16.8MgCha−1) and pole wood plantations (112.36±23.9Mgha−1) store large amounts of carbon. Together with local maize fields (69.45±12.3MgCha−1), teff fields (69.51±6.5MgCha−1) and grazing lands (76.90±10.3MgCha−1) these non-forest land uses play an important role in a prospective ‘high-carbon-stock rural-development’ under a REALU framework. A REDD+ approach, applying a stringent forest definition that disqualifies for agriculture and a 30% canopy cover threshold, would only account for 24GgC in the 106ha landscape window. Applying the canopy cover threshold alone, would triple the amount to 72GgC, while a REALU project would account for the whole 116Gg landscape carbon. The biodiversity assessment, based on tree community composition and Hill’s diversity indices, indicated important biodiversity co-benefits under a REALU approach. Biodiversity indices such as the Hill’s N1 diversity of abundant tree species showed a strong positive correlation with local carbon stocks (R2=0.56). Since the cover of indigenous forest is reduced to only 7% of the landscape window’s area, most of the remaining trees and biodiversity can be found within the surrounding landscape mosaic. Semi-forest coffee production fragments for example still harbour almost half of all encountered native tree species. An interesting result of the simultaneous biodiversity assessment was that a regrouping of plots based on tree biodiversity provides a more precise and cost efficient way to assess carbon stocks, reducing the number of plots needed with 23%, to achieve the same precision level.