Land use and cover change and water quality of tropical wetlands under anthropogenic pressure: A case study of marshlands in the Kaziba chiefdom in South-Kivu province, Eastern DR Congo

Abstract

Wetlands provide goods and ecosystem services to communities and play an important socio-economical role during dry seasons and/or droughts. However their role in nutrient stocking is poorly documented. These ecosystems are currently under anthropogenic pressure for the last decades. This study (i) assessed the land use and cover changes in and around wetlands located in the eastern Democratic Republic of Congo (DRC), (ii) characterized their water quality, and (iii) assessed the effect of those changes on the nutrients retention capacity (NRC). Based on a case study in three wetlands namely Luzinzi, Nkombo, and Kalamba, all located in the Walungu territory. Supervised classification based on Support Vector Machine (SVM) of very high spatial resolution satellite (of 1985, 2015, and 2021) was used to assess land use and land cover change. Water samples were taken (in 2018 and 2019) for characterization at the inlet and outlet of each marshland, and the nutrients retention capacity (NRC) was assessed. Results show that these wetlands have undergone significant changes in terms of land use and occupation, with previously woodland and herbaceous areas becoming bare soil, cultivated lands, and built-up areas, respectively. The ability of the marshes to purify the water and its quality is not affected by all these changes. The study shows that the water quality analysis of the streams draining the marshes was rather good, and a very good value was obtained for salt (Sodium Absorption Ratio: SAR). However, these marshes have a very low (if any) nutrient retention capacity. Future interventions should alleviate human pressure on these ecosystems while focusing efforts on ecological function maintenance or restoration.