[Show abstract][Hide abstract] ABSTRACT: Aim Species in the tropics respond to global warming by altitudinal distribution shifts. Consequences for biodiversity may be severe, resulting in lowland attrition, range-shift gaps, range contractions and extinction risks. We aim to identify plant groups (growth forms, families, endemic status) with higher than average risks.Location South Ethiopian highlands.Methods Based on observational data from mainly unexplored and remote mountain regions, we applied a published model to project the consequences of an upward shift of thermal site conditions on the altitudinal distribution of 475 plant species. Annual average temperature increases of up to 5 °C were evaluated. Differences between groups of species were analysed by a permutation procedure and Generalized Linear Models.Results Because of a limited regional species pool, even mild warming is projected to create strong potential risks concerning lowland attrition, i.e. the net loss of species richness because of upward range shifts in the absence of new species arriving. Likewise, many species are expected to face range-shift gaps, i.e. the absence of an overlap between future and current altitudinal ranges already under mild warming scenarios. Altitudinal contractions and mountain-top extinctions will potentially become important when warming exceeds 3.5 °C. Mean area per species is projected to decline by 55% for the A2 emissions scenario (+4.2 °C until 2100) because of the physical shape of the mountains. Higher than average vulnerability is expected for endemic species as well as for herbs and ferns. Plant families that are especially threatened are identified.Main conclusions Lowland biotic attrition and range-shift gaps as predicted by a simple model driven by shifts of isotherms will result in novel challenges for preserving mountain biodiversity in the inner tropics. Whereas contractions of occupied area are expected to threaten endemic and already endangered species in particular, we suggest that conservation priorities can be identified based on simple prognostic models even without precise regional warming scenarios.
Diversity and Distributions 06/2010; 16(4):593 - 605.
[Show abstract][Hide abstract] ABSTRACT: Questions: Do growth forms and vascular plant richness follow similar patterns along an altitudinal gradient? What are the driving mechanisms that structure richness patterns at the landscape scale?Location: Southwest Ethiopian highlands.Methods: Floristic and environmental data were collected from 74 plots, each covering 400 m2. The plots were distributed along altitudinal gradients. Boosted regression trees were used to derive the patterns of richness distribution along altitudinal gradients.Results: Total vascular plant richness did not show any strong response to altitude. Contrasting patterns of richness were observed for several growth forms. Woody, graminoid and climber species richness showed a unimodal structure. However, each of these morphological groups had a peak of richness at different altitudes: graminoid species attained maximum importance at a lower elevations, followed by climbers and finally woody species at higher elevations. Fern species richness increased monotonically towards higher altitudes, but herbaceous richness had a dented structure at mid-altitudes. Soil sand fraction, silt, slope and organic matter were found to contribute a considerable amount of the predicted variance of richness for total vascular plants and growth forms.Main Conclusions: Hump-shaped species richness patterns were observed for several growth forms. A mid-altitudinal richness peak was the result of a combination of climate-related water–energy dynamics, species–area relationships and local environmental factors, which have direct effects on plant physiological performance. However, altitude represents the composite gradient of several environmental variables that were interrelated. Thus, considering multiple gradients would provide a better picture of richness and the potential mechanisms responsible for the distribution of biodiversity in high-mountain regions of the tropics.
Journal of Vegetation Science 03/2010; 21(4):617 - 626.
[Show abstract][Hide abstract] ABSTRACT: This study evaluated changes in land cover in the Chemoga watershed, headwater to the Blue Nile. Two sets of aerial photographs (1957 and 1982) and a multispectral Spot image (1998) were used as inputs to produce 3 GIS-based land cover maps of the area. The results show that during the last 41 years, forest cover increased at a rate of about 11 ha per annum in the 36,400-ha watershed. Woodlands and shrublands decreased between 1957 and 1982 but increased between 1982 and 1998, approximately to their previous levels. Farmland and settled areas gained from the other cover types (13% increase) in the first period but lost around 586 ha (2% decrease) in the second. Grassland and degraded land decreased, accounting for 4.8% of the total area of the watershed in 1982 and 3.5% in 1998, as against 9.6% in 1957. Riverine trees suffered the greatest destruction, shrinking by 79% over the 4 decades; much of this decline was due to cultivation. Marshlands increased in the first period and decreased in the second. A new pond emerged amid the marshlands between 1982 and 1998. Population growth and the associated demand for land and trees was the major driving force behind the changes. This study shows that the deforestation trend was reduced and even partly reversed in the area because local people planted trees as a source of fuel and income. This trend ought to be encouraged through appropriate interventions—in particular by promoting planting of local species rather than eucalyptus—to increase not only economic but also ecological benefits. Indeed, the current state of land cover and its dynamics have environmental implications at the local scale and beyond. Hence, environmental management for sustainable development requires interregional and international cooperation.
[Show abstract][Hide abstract] ABSTRACT: Land degradation in the Ethiopian highlands is considered to be one of the major problems threatening agricultural development and food security in the country. However, knowledge about the forces driving the long-term dynamics in land resources use is limited. This research integrates biophysical information with socio-economic processes and policy changes to examine the dynamics of land resource use and farmers' livelihoods in the Beressa watershed for over 40 years during the second half of the 20th century. It was found that there have been substantial dynamics in land resource use in the area. The natural vegetation cover has been extensively cleared, although most of the cleared areas have since been replaced with plantations. Grazing land has expanded remarkably at the expense of cropland and bare land. However, the expansion of cropland was minimal over the 43-year period despite a quadrupling of the population density. Yields have not increased to compensate for the reduction in per capita cropland, and the soil quality appears to be not that good. Though the farmers perceived it otherwise, the long-term rainfall pattern has improved. In response to soil degradation, water shortage, socio-economic and policy changes, farmers have tended to gradually change from annual cropping to tree planting and livestock production to cope with the problems of soil degradation, water scarcity and smaller farms. Income diversification through the sale of wood and cattle dung is becoming a major livelihood strategy. Apparently, however, little attention has been paid to investments in soil and water conservation (SWC) and local soil fertility amendments. In particular, increased erosion and related high nutrient losses in sediments, as well as the removal of potentially available soil nutrients through the sale of manure threatens to damage agricultural sustainability in the area.
Journal of Environmental Management 07/2007; 83(4):448-59.
[Show abstract][Hide abstract] ABSTRACT: In the Ethiopian highlands, land degradation resulting from soil erosion and nutrient depletion is a serious environmental and socio-economic problem. Although soil and water conservation techniques have extensively been introduced over the past decades, sustained use of the measures was not as expected. Based on data obtained from 147 farming households, this paper examines the determinants of farmers' adoption and continued use of introduced stone terraces in an Ethiopian highland watershed. A sequential decision-making model using the bivariate probit approach was employed to analyze the data. The results show that the factors influencing adoption and continued use of the stone terraces are different. Adoption is influenced by farmers' age, farm size, perceptions on technology profitability, slope, livestock size and soil fertility, while the decision to continue using the practice is influenced by actual technology profitability, slope, soil fertility, family size, farm size and participation in off-farm work. Perceptions of erosion problem, land tenure security and extension contacts show no significant influence. Further, the results indicate the importance of household/farm and plot level factors in farmers' conservation decision. It is therefore concluded that 1) analysis of the determinants of adoption per se may not provide a full understanding of the range of factors influencing farmers' decision of sustained investments and 2) conservation interventions should focus not only on the biophysical performance of the measures but also on economic benefits that can be obtained at reasonable discount rates to the farmers in order to enhance sustained use of the measures.
[Show abstract][Hide abstract] ABSTRACT: This study examines farmers’ acceptance and adoption of soil and water conservation (SWC) technologies that were claimed by the implementing agency to have been executed in a farmer-participatory approach in a representative micro-watershed (the Digil watershed) in the north-western highlands of Ethiopia. Multiple methods of social research were employed to generate the data. The results reveal that involvement of the farmers was essentially limited to ‘participation by consultation’ and the farmers were rather persuaded to implement the conservation measures. A large majority of the farmers, however, acknowledged that the introduced conservation technologies were effective measures against soil erosion and for improving land productivity. Notwithstanding, the sustainable adoption and widespread replication of the technologies seemed unlikely. The major factors that were discouraging the farmers from adopting the technologies on their farms were found to be labour shortage, problem of fitness of the technologies to the farmers’ requirements and farming system circumstances, and land tenure insecurity. The study underscores that many of these problems were also basically related to lack of a genuine involvement of the farmers in the conservation effort and concludes by suggesting that future SWC interventions should carefully pursue a farmer-participatory approach.
[Show abstract][Hide abstract] ABSTRACT: Farmers’ decisions to conserve natural resources generally and soil and water particularly are largely determined by their
knowledge of the problems and perceived benefits of conservation. In Ethiopia, however, farmer perceptions of erosion problems
and farmer conservation practices have received little analysis or use in conservation planning. This research examines farmers’
views of erosion problems and their conservation knowledge and practices in the Beressa watershed in the central highlands
of Ethiopia. Data were obtained from a survey of 147 farm households managing 713 fields during the 2002/2003 cropping season.
In-depth interviews and group discussions were also held with the farmers to obtain additional information. The results show
that 72% of the farmers reported erosion problems, and they recognized that conservation was necessary. However, they considered
erosion to be severe mostly when visible signs – rills and gullies – appeared on their fields. The majority of the farmers
believe that erosion could be halted, and they use a range of practices for erosion control and fertility improvement. These
include contour plowing (83%), drainage ditches (82%), and stone terraces/bunds (73%). Nevertheless, despite decades of conservation
intervention in the area, it appears that most farmers have developed negative attitudes towards externally recommended measures.
The research concludes that under the conditions present in the Ethiopian central highlands, soil and water conservation interventions
should consider farmers’ conservation knowledge and practices to improve acceptance and adoption of the recommendations.
Agriculture and Human Values 02/2006; 23(1):99-108.
[Show abstract][Hide abstract] ABSTRACT: This study appraises the effects of land use on soil properties in a typical watershed in the northwestern highland of Ethiopia. Soil samples were collected from major land use types in the watershed: natural forests, cultivated lands, grazing lands and Eucalyptus plantations. The natural forests served as a control against which to assess changes in soil properties resulting from the establishment of the other land use types. Samples were taken at two depths (0–15 and 15–30 cm) in the upstream and downstream areas of the watershed and analyzed for a range of soil properties. The soils in the cultivated fields, grazing lands and Eucalyptus plantations showed significantly higher sand content, but lower Ca2+ and Mg2+ contents and cation exchange capacity (CEC) compared to soils under natural forests. Eucalyptus soils had a statistically significant higher bulk density (BD) than soils under the other three land use types. The forest and Eucalyptus soils also differed significantly from each other in their soil organic matter (SOM) and total N contents. A significant difference in available P among soils of the four land use types was caused by the difference between cultivated and Eucalyptus soils. In contrast, the distribution of soil silt fraction Na+, K+ and pH values did not differ among the four land use types. Significant differences in many of the soil properties were also observed between soils in the two sampled villages. The study underscores the need for policies and strategies for sustainable land use that will attune objectives of economic development to environmental management at the regional and local levels.
[Show abstract][Hide abstract] ABSTRACT: Soil erosion by water is recognized to be a critical economic problem in highland Ethiopia. However, nearly all the available information about its severity and economic costs are extrapolated from plot and micro-watershed level studies which are too few in number to represent the diverse environments of the country. Moreover, plot and watershed level studies do not show actual soil losses from cultivated fields, while understanding the magnitude of soil loss at the field scale is important for practical conservation planning. This paper reports results of field-scale soil erosion assessment that employed a survey methodology for rills and was conducted over two wet seasons (the years 2000 and 2001) at two sites, Kechemo and Erene, located in the upstream and downstream reaches of the Chemoga watershed, northwestern highland Ethiopia. The two wet seasons average rill erosion magnitudes were 13.5 Mg ha−1 in the Kechemo and 61 Mg ha−1 in the Erene. Assuming that interrill erosion contributes 30%, actual soil losses were around 18 Mg ha−1 in the Kechemo and 79 Mg ha−1 in the Erene. These estimates, which are well in agreement with results obtained by measurements in a nearby experimental micro-watershed, reveal that soil erosion is a threat to agricultural production in the study area and conservation measures are needed. Soil erosion showed significant spatial (between and within the two sites) and temporal variations. Hence, soil and water conservation (SWC) measures that fit well into local-scale circumstances will be realistic and acceptable to the farmers. Additionally, the problem of soil erosion should be tackled in the watershed context, because there is a strong physical interdependence between upstream and downstream areas. Finally, the study confirms that the rill survey approach gives good semi-quantitative information on soil erosion in real life situations of diverse farming and land use practices in a fast and inexpensive way; and it is commendable for practical conservation-oriented soil erosion assessment purposes.
[Show abstract][Hide abstract] ABSTRACT: Soil erosion is a widespread problem on cultivated fields in northwest Ethiopia. Plot level survey studies of soil erosion and conservation are few and far fewer have involved farmers in their assessments of the erosion process and farmers' conservation efforts. This paper presents the outcome of a farmer-participatory research conducted at two rural communities, Dubi and Gayta, in Dangila Woreda (district), in the northwestern highlands of Ethiopia. The study estimated the extent of soil erosion from tree root exposure measurements and identified farmers' soil and water conservation (SWC) practices by categorizing the farmers into three income groups: poor, medium and rich households. Data were collected from 31 plots between May and October 2010. Descriptive statistics and analysis of variance (ANOVA) were used to analyze the data. The results indicate average rates of soil erosion to be about 1.26 mm year -1 , but rates varied from 1.94 mm year -1 on seriously affected sites to 0.21 mm year -1 on the relatively less affected ones. No statistically significant difference was observed in soil loss between the three household income groups. The farmers used contour farming, traditional ditches, grass and tree planting for SWC purposes. The study concluded that as the extent of soil erosion is highly variable spatially, plot and location specific SWC measures that are designed by considering farmers' indigenous knowledge will be required to control soil loss in the study area. This study demonstrates that participatory plot level tree root exposure assessment provides useful information for soil and water conservation planning.
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