Assessment of the impact of agriculture and industry on the changing geochemical regimes, macro invertebrate communities and wetland areas : a case study of Sezela estuary and wetland areas, KwaZulu-Natal.

Abstract

The Sezela estuary and wetlands make up a vast area of the Sezela in which these environments impacted by anthropogenic activities. The Sezela area is located along the south coast of KwaZulu-Natal province of South Africa in which the predominant land uses are commercial dryland sugarcane plantation cultivation and the Sezela Sugar Mill. Due to the anthropogenic activities in the area, several coastal environments have been degraded. The degradation of these environments can be detrimental to the organisms that are dependent on them for ecosystem services and even poverty-stricken people that require these environments for basic needs (Kotze et al., 2007). In addition, due to the water crisis currently in South Africa, further degrading these estuarine and wetland environments can rapidly increase the processes of drought. Therefore, assessing the quality of these environments is imperative to identify their functionality and need for rehabilitation (Macfarlane et al., 2007). The identification of estuarine and wetland functionality are conducted through field, laboratory analysis and statistical analysis. The determination of the health of the Sezela estuary was conducted through a step-by-step method which involved sediment granulometric analysis, sediment and water quality (utilisation of ICP-OES) and macro invertebrate indicators in the sediment. The health status of wetlands were determined through the PES and ecological services provided by the wetland utilising tools such as WET-Health and WET-EcoServices. It was determined that the Sezela estuary contained relatively coarse material and lacked species composition and richness due to past pollution of the estuary by the mill. The Sezela wetland areas were degraded as a result of dryland sugarcane plantation in which two of the three wetlands were predominantly impacted drastically which were the channelled valley bottom wetlands and not the floodplain wetland. It was necessary for the Sezela estuary and wetlands to be mitigated and rehabilitated in order to re-establish past conditions or conditions that will promote the return of organisms into the estuary and wetland environments. The measures that can be implemented are improve sediment and water quality, removal of alien invasive vegetation and re-vegetation with indigenous vegetation.