Relationship between Prosopis juliflora invasion and livelihood diversification in the South Afar region, Northeast Ethiopia

This study assessed the effects of Prosopis juliflora invasion on livelihood diversification and evaluated the determinants of livelihood diversification in two districts in the South Afar region of Northeast Ethiopia. Using random sampling method, 154 households and 2 focus groups composed of 10 individuals were selected from four sites in the two districts. The relationship between P. juliflora invasion and incomes obtained from P. juliflora varied across the study sites. In Awash Fentale District and Amibara District, 11.0% and 3.2% of households, respectively, earned income from P. juliflora charcoal production. In total, 14.3% of households were involved in charcoal production. In addition, 19.9% of households earned income from selling P. juliflora pods and wood materials in the two districts. With the exception of income from P. juliflora charcoal production, the sex of households did not affect incomes from other livelihood activities. Moreover, household educational attainment significantly affected income obtained from vegetables, fruits, and cereal crops. Male householders were engaged in more diverse livelihood activities than female householders. Reversing the severe invasion of P. juliflora on grazing and woodlands in the region is advisable through integrated natural resources, pastoralist participation, and multidisciplinary research strategies

Invasion of Prosopis juliflora and its effects on soil physicochemical properties in Afar region, Northeast Ethiopia

Woody species within pastures and savannas are often associated with ‘resource islands’ characterized by higher fertility under canopies trees. The aims of this study were to evaluate (1) the effects of Prosopis juliflora on some soil physicochemical properties and (2) the impacts of Prosopis invasion on soil salinity. For soil physicochemical analysis, a total of 104 soil samples from Teru and Yalo Districts were collected. The soil samples were collected from soil depths of 0e15 cm and 15e30 cm in Prosopis invaded and non invaded open grazing lands. Invasion of Prosopis had significantly affected soil pH, exchangeable Naþ, water soluble Ca2þ þ Mg2þ, water soluble Naþ, and exchangeable sodium percentage in Teru and Yalo Districts (p < 0.05). The invasion of Prosopis significantly increased soil pH (1.5%), but decreased exchangeable Naþ (24.2%), exchangeable sodium percentage (21.6%), and water soluble Ca2þ þ Mg2þ (39.9%) than non-invaded lands. Clay content of Prosopis invaded lands was higher by 19% than non invaded lands. However, sand content of soil was higher under non-invaded lands by 5.6% than Proso pis invaded lands. Most results indicated that invasion of Prosopis had positive effects on physicochemical properties and thus conducive for cereal crops and forages

Management, use and ecology of medicinal plants in the degraded dry lands of Tigray, Northern Ethiopia

An ethnomedicinal study was conducted to document the indigenous medicinal plant knowledge on the management, use, and ecology of locally important medicinal plants in Tigray, Northern Ethiopia. Ethnobotanical data were collected from 250 people, using semi-structured questionnaires, field observation and informal discussion. The ethnomedicinal use of 259 plant species mainly herbs (31 to 51%), shrubs (31 to 46%) and trees (13 to 39%) used to treat 147 human and livestock ailments were documented in the study area. The most frequently used plant part were roots (49%), followed by leaves (37%) and bark (14%)... Crushing (59%), homogenizing with ingredients (17%) and chewing (14%) were the commonly used forms of herbal preparation. Drinking (45%), smoke inhalation (12%) and tie and hold on (10%) were the most frequently used methods of application. Most of the medicinal plants are collected from the wild. The use of more than one species was reported for remedy preparations and some health problems were treated by more than one medicinal plant. Our result showed that the local communities give less attention for the management of medicinal plants as local communities consider medicinal plants as wild, have unattractive market value and lack of knowledge. The mismanagement together with loss of habitat showed that ethnomedicinal plant species used by healers are under serious threat which indicates the need for urgent attention towards their documentation, conservation and sustainable utilization

A Role for Drylands in a Carbon Neutral World?

Drylands are a critical part of the earth system in terms of total area, socioeconomic and ecological importance. However, while drylands are known for their contribution to inter-annual atmospheric CO2 variability, they are sometimes overlooked in discussions of global carbon stocks. Here, in preparation for the November 2021 UN Climate Change Conference (COP26), we review dryland systems with emphasis on their role in current and future carbon storage, response to climate change and potential to contribute to a carbon neutral future. Current estimates of carbon in dryland soils and vegetation suggest they are significant at global scale, containing approximately 30% of global carbon in above and below-ground biomass, and surface-layer soil carbon (top 30 cm). As ecosystems that are limited by water, the drylands are vulnerable to climate change. Climate change impacts are, however, dependent on future trends in rainfall that include both drying and wetting trends at regional scales. Regional rainfall trends will initiate trends in dryland productivity, vegetation structure and soil carbon storage. However, while management of fire and herbivory can contribute to increased carbon sequestration, impacts are dependent on locally unique ecosystem responses and climate-soil-plant interactions. Similarly, while community based agroforestry initiatives have been successful in some areas, large-scale afforestation programs are logistically infeasible and sometimes ecologically inappropriate at larger scales. As climate changes, top-down prescriptive measures designed to increase carbon storage should be avoided in favour of locally-adapted approaches that balance carbon management priorities with local livelihoods, ecosystem function, biodiversity and cultural, social and economic priorities

Forests, farms, and fallows: The dynamics of tree cover transition in the southern part of the uluguru mountains, Tanzania

Forests and woodlands remain under threat in tropical Africa due to excessive exploitation and inadequate management interventions, and the isolated success stories of tree retention and tree cover transition on African agricultural land are less well documented. In this study, we characterize the status of tree cover in a landscape that contains forest patches, fallows, and farms in the southern part of Uluguru Mountains. We aimed to unveil the practices of traditional tree fallow system which is socially acceptable in local settings and how it provides a buffering effects to minimize forest disturbances and thus represents an important step towards tree cover transition. We assessed land cover dynamics for the period of 1995 to 2020 and compared tree stocking for forest patches, fallows, and farms. We found that tree biomass carbon stocks were 56 ± 5 t/ha in forest patches, 33 ± 7 t/ha in fallows, and 9 ± 2 t/ha on farms. In terms of land cover, farms shrank at intensifying rates over time for the entire assessment period of 1995–2020. Forest cover decreased from 1995–2014, with the reduction rate slowing from 2007–2014 and the trend reversing from 2014–2020, such that forest cover showed a net increase across the entire study period. Fallow consistently and progressively increased from 1995–2020. We conclude that traditional tree fallows in the study site remain a significant element of land management practice among communities, and there appears to be a trend towards intensified tree-based farming. The gains in fallowed land represent an embracing of a traditional land management system that supports rotational and alternate uses of cropping space as well as providing a buffering effect to limit over-exploitation of forests. In order to maximize tree cover and carbon stocks in the farm landscape, this well-known traditional tree fallow system can be further optimized through the incorporation of additional innovations

Mismatch between soil nutrient requirements and fertilizer applications: Implications for yield responses in Ethiopia

Lack of accurate information about soil nutrient requirements coupled with limited access to appropriate fertilizers could lead to mismatch between soil nutrient requirements and fertilizer applications. Such anomalies and mismatches are likely to have important implications for agricultural productivity. In this paper we use experimental (spectral soil analysis) data from Ethiopia to examine farmers’ response to soil nutrient deficiencies and its implications for yield responses. We find that farmers’ response to macronutrient (nitrogen and phosphorus) deficiencies is not always consistent with agronomic recommendations. For instance, we find that farmers in our sample are applying nitrogen fertilizers to soils lacking phosphorus, potentially due to lack of information on soil nutrient deficiencies or lack of access to appropriate fertilizers in rural markets. On the other hand, farmers respond to perceivably poor-quality soils and acidic soils by applying higher amount of nitrogen and phosphorus fertilizers per unit of land. We further show that such mismatches between fertilizer applications and soil macronutrient requirements are potentially yield-reducing. Those farmers matching their soil nutrient requirements and fertilizer application are likely to enjoy additional yield gains and the vice versa. Marginal yield responses associated with nitrogen (phosphorus) application increases with soil nitrogen (phosphorus) deficiency. Similarly, we find that farmers’ response to acidic soils is not yield-enhancing. These findings suggest that such mismatches may explain heterogeneities in marginal returns to chemical fertilizers and the observed low adoption rates of chemical fertilizers in sub-Saharan Africa. As such, these findings have important implications for improving input management practices and fertilizer diffusion strategies

Impact of Climate Change on the Hydrology of the Upper Awash River Basin, Ethiopia

This study investigated the impacts of climate change on the hydrology of the Upper Awash Basin, Ethiopia. A soil and water assessment tool (SWAT) model was calibrated and validated against observed streamflow using SWAT CUP. The Mann–Kendall trend test (MK) was used to assess climate trends. Meteorological drought (SPEI) and hydrological drought (SDI) were also investigated. Based on the ensemble mean of five global climate models (GCMs), projected increases in mean annual maximum temperature over the period 2015–2100 (compared with a 1983–2014 baseline) range from 1.16 to 1.73 °C, while increases in minimum temperature range between 0.79 and 2.53 °C. Increases in mean annual precipitation range from 1.8% at Addis Ababa to 45.5% over the Hombole area. High streamflow (Q5) declines at all stations except Ginchi. Low flows (Q90) also decline with Q90 equaling 0 m3 s−1 (i.e., 100% reduction) at some gauging stations (Akaki and Hombole) for individual GCMs. The SPEI confirmed a significant drought trend in the past, while the frequency and severity of drought will increase in the future. The basin experienced conditions that varied from modest dry periods to a very severe hydrological drought between 1986 and 2005. The projected SDI ranges from modestly dry to modestly wet conditions. Climate change in the basin would enhance seasonal variations in hydrological conditions. Both precipitation and streamflow will decline in the wet seasons and increase in the dry seasons. These changes are likely to have an impact on agricultural activities and other human demands for water resources throughout the basin and will require the implementation of appropriate mitigation measures

Mixed-species allometric equations and estimation of aboveground biomass and carbon stocks in restoring degraded landscape in northern Ethiopia

Accurate biomass estimation is critical to quantify the changes in biomass and carbon stocks following the restoration of degraded landscapes. However, there is lack of site-specific allometric equations for the estimation of aboveground biomass (AGB), which consequently limits our understanding of the contributions of restoration efforts in mitigating climate change. This study was conducted in northwestern Ethiopia to develop a multi-species allometric equation and investigate the spatial and temporal variation of C-stocks following the restoration of degraded landscapes. We harvested and weighed 84 trees from eleven dominant species from six grazing exclosures and adjacent communal grazing land. We observed that AGB correlates significantly with diameter at stump height D 30 (R 2 = 0.78; P < 0.01), and tree height H (R 2 = 0.41, P < 0.05). Our best model, which includes D 30 and H as predictors explained 82% of the variations in AGB. This model produced the lowest bias with narrow ranges of errors across different diameter classes. Estimated C-stock showed a significant positive correlation with stem density (R 2 = 0.80, P < 0.01) and basal area (R 2 = 0.84, P < 0.01). At the watershed level, the mean C-stock was 3.8 (±0.5) Mg C ha−1. Plot-level C-stocks varied between 0.1 and 13.7 Mg C ha−1. Estimated C-stocks in three- and seven-year-old exclosures exceeded estimated C-stock in the communal grazing land by 50%. The species that contribute most to C-stocks were Leucaena sp. (28%), Calpurnia aurea (21%), Euclea racemosa (20.9%), and Dodonaea angustifolia (15.8%). The equations developed in this study allow monitoring changes in C-stocks and C-sequestration following the implementation of restoration practices in northern Ethiopia over space and time. The estimated C-stocks can be used as a reference against which future changes in C-stocks can be compared

Stochastic simulation of restoration outcomes for a dry afromontane forest landscape in northern Ethiopia.

Forest and Landscape Restoration (FLR) is carried out with the objective of regaining ecological functions and enhancing human well-being through intervention in degrading ecosystems. However, uncertainties and risks related to FLR make it difficult to predict long-term outcomes and inform investment plans. We applied a Stochastic Impact Evaluation framework (SIE) to simulate returns on investment in the case of FLR interventions in a degraded dry Afromontane forest while accounting for uncertainties. We ran 10,000 iterations of a Monte Carlo simulation that projected FLR outcomes over a period of 25 years. Our simulations show that investments in assisted natural regeneration, enrichment planting, exclosure establishment and soil-water conservation structures all have a greater than 77% chance of positive returns. Sensitivity analysis of these outcomes indicated that the greatest threat to positive cashflows is the time required to achieve the targeted ecological outcomes. Value of Information (VOI) analysis indicated that the biggest priority for further measurement in this case is the maturity age of exclosures at which maximum biomass accumulation is achieved. The SIE framework was effective in providing forecasts of the distribution of outcomes and highlighting critical uncertainties where further measurements can help support decision-making. This approach can be useful for informing the management and planning of similar FLR interventions

Controls on timescales of soil organic carbon persistence across sub-Saharan Africa

Given the importance of soil for the global carbon cycle, it is essential to understand not only how much carbon soil stores but also how long this carbon persists. Previous studies have shown that the amount and age of soil carbon are strongly affected by the interaction of climate, vegetation, and mineralogy. However, these findings are primarily based on studies from temperate regions and from fine-scale studies, leaving large knowledge gaps for soils from understudied regions such as sub-Saharan Africa. In addition, there is a lack of data to validate modeled soil C dynamics at broad scales. Here, we present insights into organic carbon cycling, based on a new broad-scale radiocarbon and mineral dataset for sub-Saharan Africa. We found that in moderately weathered soils in seasonal climate zones with poorly crystalline and reactive clay minerals, organic carbon persists longer on average (topsoil: 201 ± 130 years; subsoil: 645 ± 385 years) than in highly weathered soils in humid regions (topsoil: 140 ± 46 years; subsoil: 454 ± 247 years) with less reactive minerals. Soils in arid climate zones (topsoil: 396 ± 339 years; subsoil: 963 ± 669 years) store organic carbon for periods more similar to those in seasonal climate zones, likely reflecting climatic constraints on weathering, carbon inputs and microbial decomposition. These insights into the timescales of organic carbon persistence in soils of sub-Saharan Africa suggest that a process-oriented grouping of soils based on pedo-climatic conditions may be useful to improve predictions of soil responses to climate change at broader scales