Urban Heat Islands and Climate Inequality: A Systematic Review of Nature-Based Solutions and Spatial Approaches in European Cities

Rapid urbanisation and global warming are intensifying the Urban Heat Island (UHI) effect, posing growing risks to human health and urban liveability. In Europe, cities face rising temperatures, ageing populations, and fragmented green infrastructure, which together amplify social and climatic vulnerability. This literature review synthesises current research on the relationships between UHI, health impacts, and the role of Nature-Based Solutions (NBS) in mitigation, with a focus on spatial and demographic analysis. A systematic search of recent peer-reviewed studies was conducted through Scopus, applying inclusion criteria centred on European urban contexts and the use of Geographic Information Systems (GIS) and remote sensing for analysis. The selected literature was categorised into four thematic areas: (1) NBS for UHI mitigation, (2) health impacts of heat exposure, (3) vulnerable populations and socioeconomic inequities, and (4) spatial and remote-sensing approaches. Findings show that NBS, including urban forests, green roofs, and blue-green infrastructure, effectively reduce surface temperatures through evapotranspiration and shading, while also supporting mental well-being and social resilience. However, unequal access to greenery and limited integration of health and spatial data prevent equitable adaptation. GIS-based frameworks emerge as critical tools for mapping heat exposure, identifying at-risk groups, and guiding targeted climate-resilient planning. The review highlights the need for inclusive, data-driven urban strategies that combine ecological and social perspectives to reduce heat-related vulnerabilities in European cities.