Criteria for defining 'streets suitable for tree planting': a model applied to Matosinhos and Leça da Palmeira (Portugal)

Urban tree planting is a key strategy for enhancing environmental resilience, public space quality, and climate change adaptation.Street trees contribute to urban microclimate regulation, air quality improvement, and stormwater management, while also fostering aesthetic and social benefits.However, spatial constraints and competing urban functions often limit opportunities for their systematic integration.Ensuring tree planting aligns with pedestrian accessibility, emergency corridors, and existing infrastructure requires a structured planning approach.This study presents a model for identifying 'streets suitable for tree planting' based on spatial and functional criteria, applied to Matosinhos and Leça da Palmeira (Portugal).The model assesses key parameters such as street width, tree spatial requirements, and compatibility with essential functions, providing a strategic tool for prioritizing street tree planting efforts.This research underscores the necessity of incorporating street trees as a core urban infrastructure, rather than introducing them secondarily after other functions have been accommodated.A spatial analysis of approximately 124 km of streets revealed that 50% of the street network meets the criteria for structured tree planting, balancing tree placement with pedestrian and emergency vehicle access.Of these, 27.2 km currently lack trees, highlighting significant potential for expanding green infrastructure.Even streets that do not fully meet the model's criteria may accommodate trees under specific conditions, such as localized widenings, building setbacks, or adjacency to open spaces that create planting opportunities.While challenges remain, including spatial conflicts and species selection constraints, the model emphasizes the importance of optimizing tree size and location for greater ecological return.Species adapted to local conditions and space-efficient planting strategies are essential in more constrained settings.By identifying and mapping suitable streets, this approach supports more efficient resource allocation, fosters interdepartmental collaboration, and enhances decision-making.It provides a replicable framework for integrating trees as fundamental components of resilient and sustainable urban environments.