Urban green spaces are key to sustainable urban development, yet climate change, urban densification, and rising land and rental prices increasingly restrict access and reinforce social inequities. Sustainable Development Goal 11.7 calls for universal, inclusive access to green spaces, with environmental justice providing the normative framework. In Germany, however, visual access to urban greenery remains largely unaddressed. While legal regulations protect landscape, street or townscape views, it rarely creates new visual access. Especially for children and seniors in socio-economically disadvantaged neighborhoods, physical access to green spaces is limited. This kind of imbalance has been intensified by climate impacts and pandemics. In dense residential areas, green window views therefore represent a low-threshold form of everyday nature contact, proven to have a multidimensional impact on the urban population. This study addresses the dimension of visual green access by developing, validating, and applying a reproducible, scalable window view simulation engine based on open-source technology and open geodata. At its core lies the Green Window View Index (GWVI), supplemented by the Floor Green Window View Index (FGWVI) and Building Green Window View Index (BGWVI). This approach meets key big-data criteria like volume, veracity, scalability, and granularity, enabling evidence-based spatial analysis. Validation via semantic segmentation confirmed a promising degree of accuracy while highlighting the need to include three-dimensional building models with indoor elements, phenological dynamics of green spaces as well as the introduced framework regarding Volunteered Window View Imagery (VWVI). Empirical case studies in Bonn and Cologne, Germany show that green visibility decreases with urban density and smaller dwelling size, whereas larger apartments and less compact structures achieve higher GWVI values. In highly dense neighborhoods, seniors and children have less than half the visual access to greenery compared with the population average, reflecting distributive environmental injustices. Overall, visual green access is more evenly distributed than green space availability, indicating a compensatory potential for vulnerable groups. The findings emphasize that visibility equity is a measurable yet neglected aspect of environmental justice. Promoting vertical greening offers a low-threshold, climate-responsive means of improving visibility conditions. The work demonstrates that open geodata and open-source technology enable valid, transferable, and cost-efficient analyses of visual environmental qualities.
Anna Maria Bolte (Thu,) studied this question.