Assessing European cities with the 3-30-300 rule underscores the need for enhanced urban greening efforts

Urban green spaces are fundamental to sustainable city living, providing essential temperature regulation and social well-being. However, rapid urbanization often threatens these areas, exacerbating socio-economic disparities in access. This study evaluates adherence to the 3-30-300 rule - a guideline advocating for three trees visible from every home, 30% neighborhood canopy cover, and a park within 300 meters - across 862 European cities. Here we show that less than 15% of the studied population lives in full accordance with these criteria, while 21% reside in areas that do not meet any of the three benchmarks. Our analysis reveals strong vegetation inequalities, where higher levels of urban greenness are consistently associated with wealthier settlements. These findings indicate that most European cities currently fall short of providing equitable access to nature, underscoring an urgent need for a paradigm shift in urban planning to sustainably and equitably address the demands of growing populations.