Urbanization and vegetation effects on flying invertebrate communities

Background/Question/Methods

Urbanization associated with high human population density and land development likely results in greatly altered faunal communities relative to rural systems. Shifts in diversity and reduced abundance are particularly expected for flying insect communities, which play important roles in ecosystem function. To test this idea, we focused on whether or not communities of forest-dwelling flying invertebrates changed in composition and abundance in relation to their proximity to urbanized environments. Flying insects were sampled using fermented bait traps (plastic bottles filled with Heineken™ beer) in five urban and five rural parks located in northeastern Ohio, USA. Within each park, five traps were placed in forested habitats and five traps were set in trail-adjacent (ecotone) habitats during two three-week sampling periods (summer and fall 2021). Invertebrate samples from the 200 traps (10 parks x 10 traps x 2 sample dates) were collected and brought to the lab for identification to the lowest possible taxonomic level. Vegetation was also sampled and characterized at each trap site as it is known to influence flying insect communities and is also affected by urbanization. Ultimately, results of this study will shed light on anthropogenic impacts on flying forest invertebrates.

Results/Conclusions

Invertebrates were 2.3X more abundant in forested habitats belonging to rural parks (Nf6783 individuals) than those belonging to urban parks (Nf2958 individuals). Interestingly, habitat-specific flying invertebrate abundance was distributed differently relative to anthropogenic influence. In rural parks, forested habitats had a higher abundance of invertebrates (1.3X) when compared with trail-adjacent traps. In contrast, trail-adjacent habitats in urban parks (n=1705) host 1.4X more invertebrates than forested habitats. Across all parks and habitats, 99% of total flying invertebrate abundance was comprised of Diptera. Ultimately, forests are important habitats for invertebrate communities regardless of anthropogenic influence. While urban parks host a range of species, the proximity to urbanization results in reduced abundance and shifts in community composition of flying invertebrates in comparison with rural parks. Overall, these effects make clear the importance of conserving forested habitats in both rural and urban settings because of the ecosystem services and habitat they provide.