Arthropod assemblages in municipal solid waste landfills: decomposers or hidden hazards?

Landfills represent a cost-effective method for waste disposal but pose significant environmental and public health risks, including the spread of arthropod-borne diseases, if not properly managed. This study investigated arthropod assemblages in two municipal solid waste landfills in Maluti-a-Phofung, Free State, South Africa, and compared them with adjacent control sites. Arthropods were sampled using pitfall traps deployed in active and dormant landfill sites, as well as in adjacent pristine grassland biotopes, during both wet and dry seasons. The study identified 11 arthropod groups in the landfills, including collembolans (48%), Diptera (25%), Hymenoptera (8%), Coleoptera (8%), and spiders (6%). Results showed that landfills support significantly higher arthropod abundance and diversity compared to control sites. In the wet season, landfills recorded a total of 9,354 individuals, compared to 3,684 in control sites, while in the dry season, 1,193 individuals were recorded in landfills vs. 788 in control areas. Detritivores and predatory arthropods were notably more abundant in landfills. Dipteran families such as Muscidae and Calliphoridae were particularly prevalent in landfills during the wet season, playing key roles as decomposers while also serving as potential disease vectors. The findings highlight that landfill conditions, including waste accumulation and seasonal variations, promote diverse arthropod communities crucial for waste degradation. However, the high abundance of arthropods, especially dipterans, may indicate inadequate landfill management. To mitigate potential health risks, improved waste containment, moisture control, and remediation practices are recommended. This study is the first documented investigation of arthropod assemblages in South African landfill sites, and future research should further explore the role of detritivores in waste degradation and pollution remediation in landfills.