Mapping and understanding degradation of alpine wetlands in the northern Maloti-Drakensberg, southern Africa

Abstract

The alpine terrestrials of the Maloti-Drakensberg in southern Africa play crucial roles in ecosystem functions and livelihoods, yet they face escalating degradation from various factors including overgrazing and climate change. This study employs advanced Digital Soil Mapping (DSM) techniques coupled with remote sensing to map and assess wetland coverage and degradation in the northern Maloti-Drakensberg. The model achieved high accuracies of 96% and 92% for training and validation data, respectively, with Kappa statistics of 0.91 and 0.83, marking a pioneering automated attempt at wetland mapping in this region. Terrain attributes such as terrain wetness index (TWI) and valley depth (VD) exhibit significant positive correlations with wetland coverage and erosion gully density, Channel Network Depth and slope were negative correlated. Gully density analysis revealed terrain attributes as dominant factors driving degradation, highlighting the need to consider catchment-specific susceptibility to erosion. This challenge traditional assumptions which mainly attribute wetland degradation to external forces such as livestock overgrazing, ice rate activity and climate change. The sensitivity map produced could serve as a basis for Integrated Catchment Management (ICM) projects, facilitating tailored conservation strategies. Future research should expand on this work to include other highland areas, explore additional covariates, and categorize wetlands based on hydroperiod and sensitivity to degradation. This comprehensive study underscores the potential of DSM and remote sensing in accurately assessing and managing wetland ecosystems, crucial for sustainable resource management in alpine regions.