Effects of land restoration on the habitat integrity of rivers based on biological water quality and habitat condition assessments with a focus on the eThekwini Municipality, Durban, South Africa.

Abstract

Riparian ecosystems are natural areas that offer an extensive range of ecosystem services. Their functionality aids in diverting and mitigating the impacts of surface water runoff, thereby reducing soil erosion. Riparian ecosystems also play an important role in sequestering nutrients and organic matter. The degradation of river systems impairs riparian ecosystem health and results in dysfunction, lack of ecosystem services provision and other deleterious effects. This study examined the effect of restoring riparian habitats across two study sites in Durban, Ethekwini Municipality, South Africa. The study aimed to a) measure and assess habitat integrity across three river systems as a result of reforestation efforts, and b) monitor the biological water quality using the Mini Stream Assessment Scoring System (MiniSASS) and the Index of Habitat Integrity indices. In addition, a systematic review was undertaken to provide an introduction and background to ecological restoration work involving freshwater ecosystems in the general South African context. The Index of Habitat Integrity and MiniSASS data were collected over ten months at two sites reforested by eThekwini Municipality, which were compared with data collected from a third river site used as the reference. Two sampling points were selected per site (namely upstream and downstream). It was predicted there would be a significant difference in MiniSASS scores between river sites under reforestation and reference sites not exposed to reforestation. However, it was found that MiniSASS and Index of Habitat Integrity scores differed between and across sites. The reference site had the highest scores. The sites with greater habitat integrity had improved ecological conditions based on macroinvertebrate responses to anthropogenic disturbances. This study highlighted the important role of naturally functioning riparian habitats in cleaning water and provides a baseline for reforestation impact monitoring, as well as informing local governance strategies for restoring degraded rivers in urban areas.