Insects and the city: Conserving the little things that run our city

All species in this planet are delicately interlinked to each other in a beautifully complex network of ecological interactions. In cities, insects are key components of urban ecological networks and are greatly impacted by human activities.

That fact inspires this research paper, which aims to examines how insect functional groups respond to changes to urban vegetation associated with different management actions. We set out to investigate how herbivorous and predatory heteropteran bugs (Figure 1) were influenced by differences in vegetation structure and diversity in a series of urban green spaces throughout southeastern Melbourne including golf courses, gardens and parks.

We looked at how the species richness of herbivorous and predatory heteropteran bugs varied amongst various types of green spaces, and the effect that vegetation volume and plant diversity had on trophic- and species-specific occupancy, using  a special type of modelling framework named ‘multi-species site occupancy models’. The hierarchical structure of this framework  is composed of three levels: a level for the ecological process (e.g. species site occupancy), another for the observation process (i.e. species detectability), and the  third to account for the sampling of each species from its metacommunity.

In our recent paper, Conserving herbivorous and predatory insects in urban green space, our key findings showed that golf courses sustain higher species richness of herbivorous and predatory heteropteran bugs than parks and gardens, and that at the trophic- and species-specific levels, herbivores and predators show strong positive responses to vegetation volume. However, we also found that the effect of plant diversity is distinctly species-specific, with species showing both positive and negative responses.

Since the research results show  that high occupancy of heteropteran bugs is obtained in green spaces with specific combinations of vegetation structure and plant diversity, we suggest that green space managers should aim their management strategies and actions at promoting a synergistic combination of these two features, so as to boost the conservation value of all urban green spaces for herbivorous and predatory insects. We emphasise the significance of this in both large green spaces with simple vegetation structure and in the smaller ones such as public parks and residential gardens where a heterogeneity of planting structure and diversity is more difficult to intentionally achieve. We believe that tackling this conservation challenge could provide enormous benefits for all elements of the urban ecological networks, especially including human residents.

Recommended Paper Citation:
Mata, L., Threlfall, C. G., Williams, N. S., Hahs, A. K., Malipatil, M., Stork, N. E., & Livesley, S. J. (2017). Conserving herbivorous and predatory insects in urban green spaces. Scientific reports, 7.

First published in The Urban Observer

  • Header image: Figure 1: The alydid bug Mutusca brevicornis, a specilist grass-feeding herbivore in a golf course grassland patch in southeastern Melbourne. (Photo by Luis Mata)