Integrating NbS in compact city renewal: Preferences, constraints, and opportunities

• The potential of revitalizing compact cities with NbS was studied through a dual approach. • Surveys indicate that residents prioritize NbS services and experts emphasize conservation. • The highest potential for increasing NbS in compact cities is to retrofit rooftops. • Vertical greening on walls and linear infrastructure also helps expand NbS. • The analyzed case can raise NbS from a 15–20 % land coverage baseline to more than 30 %. Compact cities, often being praised for their sustainability advantages, face significant urban challenges (UC) due to their dense configurations and the intensifying effects of climate change. This study, conducted in Hong Kong, investigates the potential of using Nature-based Solutions (NbS) to mitigate these issues through a dual methodology—integrating surveys capturing public and professional perceptions and a novel geoinformatics analysis assessing spatial opportunities. The survey engaged 233 residents and 36 experts and found that climate change ranks as a primary concern, surpassed only by housing shortages. Residents favored NbS benefits, whereas experts prioritized ecological gains like biodiversity enhancement. Both groups, however, noted potential drawbacks including risks of animal-borne diseases and nuisances. The geoinformatics analysis evaluated nine sampling areas across three regions and identified rooftop retrofitting as a key strategy for expanding NbS coverage. Vertical greening on walls and linear infrastructure also emerged as viable methods to expand NbS. With these measures, the total NbS coverage could increase from about 15–20 % to more than 30 % in the analyzed areas. By synthesizing public preferences with spatial feasibility, this study develops a comprehensive framework for NbS deployment in compact urban environments. This dual approach bridges a critical gap in conventional urban planning by ensuring solutions are both socially relevant and technically sound.