Investigation of Urban Heat Mitigation and Thermal Maladaptation Potential from Small-Scale Green Roofs: A Case Study in Seoul

Climate change is leading to more frequent and intense heat waves, exposing urban populations to extreme heat conditions, and posing significant health risks. Many cities are adopting nature-based solutions (NbS) to mitigate urban heat, with green roofs emerging as a universal NbS. They are advantageous as they can be easily implemented in dense urban areas without requiring extra land and are generally effective in cooling. Although numerous green roof projects are implemented on a small scale, research on the effectiveness of small-scale green roofs in heat reduction is limited. Consequently, we assess the cooling potential of small-scale green roofs, identifying the traits of successful implementations and how these differ from green roofs that result in maladaptation. We utilized a quasi-experimental design methodology to improve causal inference, effectively isolating the impact of individual green roofs from background climate changes using publicly available green roof data and longitudinal satellite imagery. In our study of 11 green roof projects in Seoul, we noted that intensive-type green roofs had a cooling effect. In contrast, projects that experienced temperature increases typically featured extensive vegetation and structural elements that increased albedo. This evidence can assist decision-makers in reducing risks of maladaptation and enhancing effective adaptation practices. This method is expected to support governments, especially those with limited budgets, in efficiently managing urban heat, reducing trial and error. Ultimately, our research holds the potential to significantly contribute to the sustainability of society and the environment.