Developing an indicator for assessing wetland degradation based on soil quality, water drainage, and human-related landscape factors

Due to environmental stress and anthropogenic pressures, wetlands are declining and being degraded in areas with increased settlement and road construction. Although various indicators have been developed to assess ecosystem degradation, few studies have specifically addressed wetland soil degradation and its underlying drivers. In this study, we attempted to create a Wetland Soil Degradation indicator (WSDI) and identify its driving factors in a contrasting landscape characterized by significant anthropogenic changes. We selected the eastern Democratic Republic of Congo (DRC), a region where severe wetland degradation primarily caused by agriculture and brickmaking activities has been reported. We combined Geographic Information System (GIS), remote sensing approaches and soil profile analysis. For landscape change, four concentric circles from the two wetland centers were made. A WSDI was developed and refined using the minimum data set (MDS) coupled with multivariate statistical techniques to assess the level of wetland degradation. For the case study, an overall WSDI score averaged 0.52 across the two sites. Higher degradation was observed in brickmaking (0.62) compared to agriculture zones (0.52), while intact zones had a lower score (0.28). Degradation was also more severe in completely drained areas (0.72) than in partially (0.48) and intact, non-drained areas (0.28). Significant correlations were found between the level of degradation and human-related landscapes, notably the proximity to villages, rural settlements, and roads. Wetland degradation was strongly linked to road accessibility and the distance to human-related landscapes. The indicator confirmed a gradual degradation pattern, starting from the wetland edges and moving toward the center. Overall, the WSDI is essential for diagnostic purposes before developing a restoration plan to ensure sustainability and to question these critical ecosystems’ future.