Ecosystem Services on Green Roofs in the Southeastern United States: Effects of Management, Age, and Other Variables

Widespread urbanization is causing land cover changes that have dramatic impacts on the structure and functions of natural ecosystems. To mitigate these impacts, green infrastructure (vegetated urban habitat) is implemented to improve environmental quality and protect crucial ecosystem services. As roofs can represent up to 32% of horizontal surfaces in a typical urban setting, they are ideal candidates for green infrastructure. However, despite their potential and growing implementation in cities across the world, green roofs remain very poorly researched, particularly regarding ecosystem services and management practices, compared to other kinds of green infrastructure. This study examines ecosystem services provided by green roofs in 13 urban locations across three states in the Southeastern United States: Asheville, NC; Atlanta, GA; Chattanooga, TN; Knoxville, TN; and Nashville, TN. The ecosystem services studied are assessed through proxies including invertebrate abundance and diversity, decomposition rate and stabilization factor, plant diversity and frequency, and substrate composition. Samples of each proxy, except substrate, were collected over the course of 6 months from March to August 2024. Management intensity (high and low) shows a statistical significance on several variables. High management has a negative on effect on plant and invertebrate biodiversity and a positive effect on soil decomposition rates. Also, soil moisture of the green roofs showed a significant negative effect plant diversity and positive effect on plant frequency. With inverse results for soil temperature on plant diversity. Individual maintenance practices such as irrigation, weeding, and chemical treatments only showed significance for a few proxies: decomposition rate, plant diversity and frequency, and OM levels. In general, roofs with lower levels of management exhibit higher biodiversity as compared to their high-management counterparts. This aligns with many other urban habitats, such as residential and commercial landscapes, where intensive management often aims to reduce biodiversity. Interestingly, decomposition rates show a significant increase with higher management. As green roofs in the United States are sparsely researched, this study helps examine the complexity of a green roof ecosystem and provide insight onto the best management practices to promote ecosystem services.