Impacts of climate and climate change on water and vegetation dynamics in Horn of Africa drylands

Abstract

Dryland regions, including the Horn of Africa, are particularly vulnerable to the impacts of drought and are expected to be disproportionately affected by climate change. As such, comprehending the interactions between climate, rainfall, hydrology, and plants in these regions is crucial for devising effective strategies to mitigate the impacts of drought. However, understanding the impacts of climate in the Horn of Africa, particularly in the drylands, is challenging due to the scarcity of meteorological stations. Consequently, generators and consumers of climate information typically rely on coarse-resolution rainfall data, produced through spatial and temporal averaging from gauging stations and remote sensing products, to inform economic and livelihood decisions in drylands. The impacts of using these coarser products to assess soil moisture and deep percolation, however, remain largely unquantified. In addition, there are significant uncertainties regarding how a warming climate, which is projected to alter the delivery of precipitation, may affect the evolution of soil moisture and the overall water balance in drylands and their implications for natural vegetation, a source of fodder in a dominant pastoral livelihood zone. To address these gaps in knowledge, this study utilized hydrological modelling techniques to examine the sensitivity of soil moisture to the temporal resolution of rainfall, modelled the effects of rainfall characteristics on water partitioning through the soil under various climate scenarios, and employed remote sensing to map vegetation dynamics in the Horn of Africa drylands over the 1984-2020 period. The results were analysed to distinguish between shallow and deep-rooted plant responses to precipitation. The hydrological modelling was then linked to the vegetation data to better understand changes in water availability to plants at different depths, and to examine the connections between climate, rainfall, hydrology, and plants in drylands. The outcomes of this research have provided valuable insights into the complex interactions between climate, rainfall, hydrology, and plants in dryland environments. They have highlighted the importance of considering the temporal resolution of rainfall when studying soil moisture and have demonstrated the significant impact of rainfall characteristics on water partitioning through the soil. The use of remote sensing to map vegetation dynamics in the Horn of Africa drylands has allowed for a deeper understanding of the response of shallow and deep-rooted plants to precipitation, and the linking of the hydrological modelling to the vegetation data has provided a more comprehensive examination of the connections between climate, rainfall, hydrology, and plants in drylands. These findings have important implications for the development of strategies to mitigate the impacts of drought in dryland regions.

Date of Award	19 Mar 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Katerina Michaelides (Supervisor), Michael M. Singher (Supervisor) & Rafael Rosolem (Supervisor)