Vulnerability assessment of wetland ecosystems to water demand, climate variability and land-use/cover change: The case of Die Vlei wetland, Eastern Cape province, South Africa

Abstract

Water scarcity is a major challenge in many different countries, particularly arid and or semi-arid like South Africa. Wetlands are one of the freshwater ecosystems that may assist in alleviating water scarcity because they are valuable not only as a water source for humans but also as an ecosystem of animals and plant species. However, wetlands have been experiencing rapid rates of vulnerability/risk due to alterations by population growth leading to enhanced water demand, climate variability, and human activities leading to land cover/land-use changes. Geographical Information Systems (GIS) and Remote Sensing (RS) are less financially taxing methods useful in studying water scarcity, as shown in this study. The study begins with a literature review presentation based on a desk study from predominantly academic publications and additional municipal and consultancy reports on the wetland ecosystem’s vulnerability/risk and focuses on applying GIS & RS in related studies. After that, the study conducts a vulnerability assessment using the Ramsar Convention’s wetland vulnerability assessment using the theoretical framework stages using GIS and RS technologies. The study hypothesizes that water demand, climate variability, and land-use/cover changes (LULC) are the tri-factor responsible for wetland vulnerability. It begins the assessment by first quantifying wetland water demand using the wetland water budget, ecosystem services and the Penman-Montheith-FAO (ETo) evapotranspiration index. Secondly, objectively representing climate variability on wetland vulnerability using trend analysis to measure rainfall and temperature variability. Thirdly, reconstructing LULC changes from multi-date remotely sensed SPOT imagery over ten years from 2007 to 2017 to identify and monitor impacts of trends. The vulnerability was assessed through a Principle Component Analysis (PCA) that identified relevant variables and Multi-Criteria Evaluation (MCE) to evaluate the wetland’s exposure. The study concludes that there is evidence of a possible increase in water demand whilst climate variability, which is estimated to have a 39% contribution to the wetland dynamics, is characterised by a decrease in precipitation and an increase in temperatures. Lastly, LULC trends showed a marked increase in domestic and commercial farming, and farming has been identified as a wetland stressor of note.Thesis (MPhil) -- Faculty of Science and Agriculture, 202