Six PhD student projects well underway

PhD students participating in the first phase of the Woody Weeds project presented their project outlines and some initial results during the recent project meeting in Adama, Ethiopia. The six students play an important role in the woody weeds project and we were excited to learn about their progress. In addition, four MSc students are carrying out research on the socio-economic and ecological aspects of the woody weeds project. The students have established active collaborations among themselves and they work together to collect field data. It is expected that this  interdisciplinary collaboration will contribute to achieving project outcomes and also to the professional development of the students. Below, we introduce the PhD students and give a brief summary of their research topics, objectives and methodologies.


MSc and PhD students of the Woody Weeds project in Adama, Ethiopia. Front row: Ms Maria Loreto Castillo, Ms Purity Rima Mbaabu and Ms Amina A Hamad. Back row: Mr Anteneh Abebe, Mr Hailu Shiferaw Desta, Mr Ousmane Seid, Mr Theo Linders and Mr Ketema Bekele. Photo credit: Urs Schaffner.

PhD students and research topics:

Maria Loreto Castillo (CIB, South Africa) – This research focuses on understanding the ecological-evolutionary dynamics that underlie the extraordinary invasive success of Prosopis species globally, with a focus on Kenya and Ethiopia. From a global perspective, Maria aims to use population genetic techniques and Prosopis individuals from invasive populations around the world to assess the incidence and extent of hybridization. On the local level, she aims to integrate genomic simulation modelling, experimentation and historic information about the introduction of the individuals to a) evaluate whether some species and/or their hybrid offspring are more likely to undergo range expansions, b) link dispersal ability and survival capacity to new habitat characteristics such as soil conditions or presence of pastoralist routes, c) identify potential routes of spread from the first planted individuals. A final important objective is to evaluate how this new knowledge on invasion processes can be applied to develop effective management options such as biological control.


Ketema Bekele (Haramaya University, Ethiopia) – The general objective of this PhD research is to measure the impact of woody weeds on rural livelihood and ecosystem services in East Africa, specifically Prosopis in Ethiopia and Kenya, and Lantana in Ethiopia and Tanzania. This research will (i) evaluate impact heterogeneity of these woody weeds on those aspects of biodiversity and ecosystem services that are important to the livelihoods of rural households; (ii) estimate the economic values that households place on the studied woody weeds and their impacts; and (iii) identify the measures that households take to mitigate the negative impacts. To address these objectives, context-based household questionnaires, focus group discussions and key informant interviews will be applied. Descriptive statistics and econometric models will be used for data analysis.


Theo Linders (CABI Switzerland) – This PhD thesis focuses on assessing the effects of two woody weeds, Lantana camara and Prosopis juliflora, on biodiversity and ecosystem services in East Africa. Data will be collected in the field along a cover gradient, in four regions in Ethiopia, Kenya and Tanzania. The effect of these woody weeds will be analysed for individual ecosystem services and for combined ecosystem services for each region. The effects will also be compared between the regions to look for regional and species-specific differences. Additionally, the ecological data will be combined with socio-economic data on the impacts of woody weeds in the same regions (see Ketema Bekele, above). This combination will allow an assessment of how the effects of invasive species on ecosystem services change with increasing cover of these woody weeds measured by both environmental and socio-economic data. It will therefore enable us understand the full impact of woody weeds  on the study area.


Hailu Shiferaw Desta (WRLC, Ethiopia) – The goal of this research is to spatially assess the historical and current, and to model the potential future distribution of Prosopis juliflora in Afar Region, Ethiopia. Based on these distribution maps, change in land use and land cover  will be mapped and quantified. Additionally, fractional cover maps of Prosopis juliflora will be generated. Based on identified key factors associated with invasion of Prosopis juliflora (elaborated based on the findings of the other PhD students as well as the entire project team), areas at risk of future invasion in Afar Region will be spatially predicted. In order to understand and quantify impacts on water, Prosopis tree water consumption will be measured at the plot scale. These measurements will then be spatially up scaled to district and regional level. Costs and benefits of above ground biomass ( as well as land use and management) will be spatially assessed and quantified.


Purity Rima Mbaabu (KEFRI, Kenya) – The goal of this research is to spatially assess the historical and current, and to model the potential future, distribution of Prosopis juliflora in Baringo County, Kenya. Based on these distribution maps, change in land use and land cover will be mapped and quantified. Additionally, fractional cover maps of Prosopis juliflora will be generated. This will be done with the help of spectro-radiometric field measurements. Also, when modelling the future spread potential of the species, different climate scenarios will be considered. Purity’s study set up is within the agro-pastoral communities in Baringo, situated along the Great Rift Valley in Kenya. In order to understand and quantify (spatial and monetary) impacts on biodiversity as well as agro-pastoral livelihoods she will work in close collaboration with other PhD students in the project team who assess these impacts on plot level and also conduct socio-economic household surveys. Besides that she will conduct participatory mapping exercises  in agro-pastoral communities. Costs and benefits of respective land cover and land use will be spatially mapped and quantified for the entire Baringo County.


Amina A Hamad (Sokoine University of Agriculture, Tanzania) – The research aims at assessing the distribution and abundance of Lantana camara in the East Usambara Mountains, Tanzania by using WorldView-3 satellite data as well as spectro-radiometric field measurements. Based on these mapping results, a fractional cover map of L. camara will be generated. Future potential invasions of L. camara shall be conducted by assessing historic L. camara distribution using a combination of aerial photos and participatory mapping. Furthermore, impacts of L. camara on plant species diversity and selected ecosystem services will be quantified and mapped by working in close collaboration with other PhD students who assess these impacts on field plot and household level. Their collected data will be used to upscale the impacts to the entire study area. Plot level work done by this PhD includes  field runoff experiments to quantify impacts of L. camara on soil loss and water quality.  As a result of the spectro-radiometric field work, this PhD research will establish a spectral library of important plant species (introduced as well as native) present in the study area. The data will then be used to further analyse their spectral separability.