Acute challenges and solutions for urban forestry in compact and densifying cities

Many cities are becoming increasingly dense, bringing more impervious surface and less vegetation-growing space. Dense urban environments demand ecosystem services of urban trees, yet growth conditions are difficult. Innovative planning and management could permit coexistence of urban fabric and nature. This study reviews three groups of constraints to urban forestry in dense areas: (1) spatialsubaerial, (2) subterranean-root, and (3) institutional and social. Integrated proposals are developed to overcome the constraints and optimize the provision and benefits of urban forests despite the stresses. They are based on a typology of compact-city types and tripartite classification of urban land covers. Embracing the landscape-ecological and institutional-social dimensions, they refer to both primary and secondary compact cities. The quality and coverage of urban forests could be improved by pragmatic, actionable and tailor-made solutions. Precision green-space planning for in situ and ex situ densification could tackle the multiple and intractable limitations and prepare redevelopment and new development areas for greenery preservation and installation. Urban forestry could better integrate urban form and density with comprehensive spatial, temporal, and institutional visions. Copyright © 2018 American Society of Civil Engineers.