Bridging the Green Gap: An Evaluation of the 3-30-300 Rule in European Cities

As the world becomes increasingly urbanized, cities play a crucial role in addressing global challenges, including environmental sustainability and human well-being. The presence of natural green spaces in urban areas is essential for mediating the interaction between the built environment and humans, providing ecosystem services, and promoting population health and wellbeing. However, the demand for urban green spaces is often at odds with urbanization, densification, and sprawl, leading to the loss and fragmentation of urban natural areas. 

In response to these challenges, the European Union has introduced a range of policies and legislations, such as the New Urban Agenda, the EU Biodiversity Strategy for 2030 and the Nature Restoration Law. Along with such initiatives Konijnendijk (2022) launched a new rule of thumb for urban forestry and urban greening: the 3-30-300 rule. The 3-30-300 rule aims to ensure that everyone should be able to see at least 3 well-established trees from their home, workplace, or place of learning; have at least 30 % tree canopy cover in their neighborhood; and live within 300-m of a high-quality public green space (at least 0.5 ha in size).

This study presents the first comprehensive evaluation of the 3-30-300 rule across 894 European cities, using recent data on urban green space distribution, tree cover density, and human settlement. The analysis reveals significant disparities in the distribution and access to urban green areas, with only 1.7% of the total population in European cities living in accordance with the 3-30-300 rule. There are no EU cities where more than 15% of the population satisfy the rule, and just 10 cities where this percentage is larger than 5%. 

Our results show that there is a clear gap in the distribution and access to urban green areas across European cities. Thus, the projected urban population growth in European regions underscores the need for a paradigm shift in urban planning. The recent decade (2010-2020) has witnessed a significant increase in urban population (+16% on average) and urban area expansion (+2.3% on average) within city boundaries. However, this urban growth has not been accompanied by a commensurate increase in green urban areas and tree cover density with both indicators exhibiting stable or declining trends.

Such results highlight the need for a paradigm shift in urban planning, integrating green spaces and trees within city planning to provide ecological and social benefits, including climate change mitigation and adaptation. To address this gap, targeted financial support and coordinated strategies are necessary to ensure that vulnerable cities can secure adequate quantities of green spaces and provide equitable access to these areas, ultimately promoting more resilient and sustainable urban environments.