Assessing insect functional diversity across land-use types in the West Usambara Mountains, Tanzania

This study was conducted in the West Usambara Mountains, specifically the Mgwashi Ward in northern Tanzania, in November 2024. With insect biodiversity declining globally and the lack of research on insect populations in the West Usambara, this study aimed to assess insect functional diversity and abundance across three land uses: protected area, mixed cropping, and agroforestry. Data were collected over four days using cup traps and pan traps to sample winged and ground- dwelling insects. Purposive sampling techniques were used to select study sites, and systematic random sampling was used to place study plots, transects, and traps. Two 30m x 30m study plots were created per land use, each containing two transects. Along each transect, twelve traps were placed (six of each type), therefore totaling 144 traps across all three sites. 2,426 insects were sampled across all three sites, with mixed cropping trapping the highest abundance (n = 1,014), and protected area trapping the lowest abundance (n = 580). While the protected area had the lowest abundance, according to the Shannon-Weiner Diversity Index, the protected area had the highest functional diversity (H’ = 1.70). Species in the insect population control and decomposer functional groups were found to have notably low abundances in the mixed cropping and agroforestry land uses, making these ecological services less present in these two land uses. The chi-squared test reveals an X2 (16, N = 2216) = 532.54, p < .001 difference relationship between land-use types and functional group distribution. The findings suggest that the low-intensity agriculture practiced in the Mgwashi Ward significantly affects insect functional diversity. However, more research is needed to assess how these effects on insect functional diversity lead to potential harms and benefits for the surrounding human and ecological community.