Roadside green spaces: role of tree diversity in carbon storage and thermal comfort

Abstract Roadside green spaces (RGS) are an essential part of urban environments. These provide a variety of ecosystem services, including biodiversity conservation, carbon storage, and microclimate regulation. This study aims to assess RGS for tree diversity, carbon stock, and thermal comfort along four major roads of the Jawaharlal Nehru University campus, New Delhi. An extensive belt transect survey was employed with a total of 59 plots (10 m × 5 m each) covering a 5.5 km stretch of road. RGS supported 27 tree species from 27 genera and 15 families, comprising 19 native, 6 introduced and 2 invasive species. The diversity indices indicated low dominance (D = 0.16), moderate diversity (H′ = 2.47), and moderately high evenness (J′ = 0.75). The Fabaceae family was the most dominant, with Cassia fistula having the highest IVI. However, invasive species ( Leucaena leucocephala and Prosopis juliflora ) accounted for 47.17% of the individuals. Despite the abundance, these invasive species contributed minimally to carbon stock (0.59 and 0.23 tC/m 2 , respectively), underscoring that these are neither ecologically nor sustainably beneficial. Overall, the RGS stored 0.312 tC/m 2 of carbon. These also contributed to thermal comfort regulation, with on-field measurements showing reductions in air temperature by 0.80 to 2.24 °C and land surface temperature by 3.80 to 8.37 °C during April and May 2025. This research highlights the multifunctional role of RGS while emphasizing the urgent need to manage invasive species to secure their ecological and sustainability benefits. These findings confirm the role of RGS as an effective natural cooling system for megacities such as Delhi, which experiences intensifying heat waves and rising heat stress. For urban policy and planning, this underscores the need to integrate invasive species control and proactive RGS management into city-scale heat adaptation strategies.