Biodiversity underpins ecosystem stability, resilience, and the delivery of ecological services essential to human well-being. However, global biodiversity is declining at unprecedented rates due to land-use change, habitat degradation, and climate variability. In arid and semi-arid savannahs, where ecosystems are constrained by resource scarcity these pressures intensify through bush encroachment, the densification of woody vegetation displacing grasslands. This shift undermines rangeland productivity, alters vegetation structure, and reshapes biodiversity patterns. While vegetation and livestock responses are well-studied, implications for invertebrate biodiversity, particularly arthropods as functionally critical taxa, remain underexplored. This thesis bridges these gaps via three interconnected objectives linking data integrity, ecological patterns, and management interventions in Namibian savannahs. The first assesses arthropod biodiversity data quality across global platforms (iNaturalist, GBIF) and the Namibian Biodiversity Database. Recognition (species-level identifications) and completeness (species coverage) vary markedly by arthropod order, influenced by detectability, morphology, and familiarity. Global datasets provide baselines, but national databases are vital for accuracy, advocating integrated frameworks to strengthen monitoring, conservation, and citizen science. The second study investigates effects of dominant encroaching shrubs, Dichrostachys cinerea, Senegalia mellifera, and Terminalia sericea on arthropod communities across canopy, aerial, and ground strata in wet/dry seasons. Sampling via pitfall, pan, and beating traps revealed shrub-specific compositional shifts, driven by canopy taxa. S. mellifera favoured omnivore guilds and D. cinerea favoured phytophagous. Abundance increased with ground cover but fell with woody density, highlighting habitat heterogeneity's role in sustaining diversity amid encroachment. The third objective evaluates bush thinning management practice: manual/chemical treatments at 50% (moderate) and 100% (complete) intensities. Moderate manual thinning boosted arthropod abundance, richness, and functional diversity versus complete/chemical options. Pollinators, herbivores, decomposers, and predators thrived under partial shrub thinning, preserving heterogeneity; while chemical clearing suppressed sensitive groups like Auchenorrhyncha, Opiliones, and Coccinellidae. Soil properties, including pH and nutrient concentrations, further modified arthropod responses across shrub species. In summary, the thesis presents a framework for arthropod conservation based on three pillars: robust data systems, vegetation-arthropod ecology, and balanced rangeland management that restores grasslands (e.g. 50% moderate manual shrub thinning) without causing arthropod biodiversity loss. Integrating informatics, community ecology, and restoration advances dryland resilience in African savannahs and rangeland ecosystems.
Martha Alfeus (Thu,) studied this question.