Flower-rich, less-cut road verges support butterflies in urban environments

Urban road verges, often overlooked as simple roadside greenery, can serve as valuable habitats for butterflies and other insect pollinators (Figure 1). Our recent study explored how these narrow green spaces contribute to urban biodiversity, using causal inference methods to analyse butterfly communities along major roads in Singapore.

Figure 1. A Leopard butterfly (Phalanta phalantha) nectar-feeding in a road verge.

We found that increased structural complexity (i.e., varied vegetation heights), plant richness and nectar-floral diversity, promote butterfly abundance and species richness (Figure 2). Other surrounding green spaces also further support butterfly diversity. However, high traffic density negatively affects butterfly populations, likely due to an increased risk of collisions. Interestingly, larger road verges indirectly support butterfly diversity by increasing nectar-floral diversity.

Our findings highlight that small changes, such as promoting plant diversity and allowing vegetation to vary in height, can greatly improve the quality of habitats for butterflies without the need to widen road verges (Figure 2). This study, therefore, offers valuable guidance for urban planners and policymakers, helping to shape urban green spaces that not only serve their functional role in the city but also support the creation of more resilient ecosystems. With careful planning and management, these green spaces can become valuable contributors to urban biodiversity.

Figure 2. Different cutting regimes observed across sampled road verges. (a) A recently cut road verge with uniform vegetation height, providing minimal resources for butterflies. (b) A road verge several months after cutting, featuring abundant flowering plants, especially those exceeding the previous cut height, creating a more suitable habitat for butterflies. (c) A road verge with selectively uncut vegetation, increasing structural complexity (i.e., varied vegetation heights), making it an even better habitat for butterflies.

For more details, check out our paper published in Landscape and Urban Planning, at https://doi.org/10.1016/j.landurbplan.2025.105335

How to cite this article: Priyadarshana, T. S., Woodcock, B. A., Jain, A., Martínez‐Núñez, C., Goodale, E., Lee, M., Pagani‐Núñez, E., Gebert, F., Lee, J. S. L., & Slade, E. M. (2025). The direct and indirect effects of road verges and urban greening on butterflies in a tropical city-state. Landscape and Urban Planning, 258, 105335. https://doi.org/10.1016/j.landurbplan.2025.105335