Acute canopy deficits in global cities exposed by the 3-30-300 benchmark for urban nature

Abstract

The 3-30-300 rule is a recently proposed metric that sets minimum standards for access to nature in cities for human wellbeing. It specifies that homes, schools and workplaces should have a view of 3 trees, be in a neighbourhood with over 30% tree canopy cover and be within 300 m walk of a park. This metric is an important progression for assessing urban nature because it is easy to understand, highly local, and sets a pass/fail benchmark for green infrastructure. Using datasets of over 2.5 million buildings in eight cities, we show that most buildings fail the 3-30-300 rule due to inadequate tree canopy, even in well-known global cities (the cities are Amsterdam, Buenos Aires, Seattle, Denv..