A recent study examining nature access in eight significant cities around the world revealed that most of them still lack sufficient tree canopy cover, even though there are plenty of trees available.
A recent study led by RMIT University in Australia examining nature access in eight major global cities revealed that most still lack proper canopy cover, despite abundant trees in the area.
In cities like New York, Amsterdam, Buenos Aires, Denver, central Sydney, and central Melbourne, less than 30% of buildings were located in areas with adequate tree canopy cover.
New York and Amsterdam reported nearly 0% canopy cover, even though 92% and 50% of their buildings have views of at least three trees, respectively.
This research, a partnership with the Technical University of Munich, analyzed over 2.5 million buildings across the eight cities using a developing method for assessing sustainable cities known as the ‘3-30-300’ rule.
This rule suggests that every home, school, and place of work should have a view of at least three trees, be in a neighborhood with at least 30% canopy cover, and be within 300 meters of a park.
Only Seattle and Singapore met the 30% canopy cover requirement, with 45% and 75% of buildings in these cities benefiting from sufficient shade, respectively.
Park access varied greatly; Singapore and Amsterdam scored well, while Buenos Aires and New York fell short.
The lead researcher, Dr. Thami Croeser from RMIT University, expressed concern over the number of buildings failing to meet the 30% tree canopy standard.
Given that 2023 is on record as the hottest year so far, with a quarter of the global population experiencing extreme heat, the need for more canopy cover to cool urban areas is critical, he stressed.
“Previous studies indicate that issues like depression, anxiety, obesity, and heatstroke are more common in urban locales lacking shady tree canopies and green spaces,” noted Croeser, associated with RMIT’s Centre for Urban Research.
“Canopy cover not only contributes to cooling but can also lower flood risks, enhance mental and physical health, and promote urban biodiversity.
“Research suggests we actually need at least 40% canopy cover to significantly decrease daytime air temperatures, making the ’30’ target the absolute minimum—most buildings we studied do not meet even that standard.”
Croeser also mentioned that current urban planning techniques often neglect healthy tree growth, as infrastructure needs like cabling and plumbing take precedence over tree planting.
“We must change our mindset regarding the permanence of spaces assigned to buildings and roadways and consider reallocating them to prioritize green infrastructure,” he stated.
While 30% canopy cover seems like a high goal if we keep to old practices, it’s entirely achievable with some modifications in our approach.
“At present, trees are often an afterthought; if they conflict with cabling or pipelines, we remove them or replace them with small saplings.
Incorporating trees into street designs from the outset—and working to find mutually beneficial solutions for utilities and traffic access—represents a significant shift we need to make for improvement.”
Croeser added that trees are often planted in unfavorable conditions.
“The soil is tightly packed, there’s asphalt covering them, and rainwater runs off into the gutters rather than soaking into the ground.”
Previous research indicates that if urban trees are planted in better-quality soil with sufficient room to grow, and if rainwater can directly penetrate the ground, this would facilitate the trees’ growth, helping to solve our canopy cover issue.
Urban trees are often removed or replaced with saplings, or excessively pruned, so few are able to mature into large canopy trees, except in select fortunate areas.
A new nature access metric with potential
The ‘3-30-300’ rule, developed by Dutch urban forestry specialist Professor Cecil Konijnendijk, is relatively new in Australia but is gaining traction internationally, with at least six cities across Europe, the US, and Canada adopting it in their urban forestry policies.
Konijnendijk created the benchmark to establish a ‘bare minimum’ standard for nature in urban settings.
“Integrating more parks and trees into cities is a complex challenge, so I recognized the need for a straightforward measurement that could clarify the goal and be based on proven data,” he said.
“I examined decades of research linking nature to human health and found that access to nature, tree canopy cover, and parks are vital for mental well-being, physical activity, and protection from heat waves.”
Professor Wolfgang Weisser from the Technical University of Munich remarked that metrics evaluating the sufficiency of green infrastructure related to human well-being at the neighborhood level are still uncommon.
“Many of the current metrics we use are insufficient, while the ‘3-30-300’ standard effectively emphasizes the need for nature in places where people live and work,” Weisser noted.
A municipality with few trees lining its streets but a couple of well-wooded parks may score well on aggregated metrics for canopy and greenery per capita, yet it could be viewed as inadequate under the localized ‘3’ and ’30’ criteria.”
The research team collaborated with Dutch firm Cobra Groeninzicht (Green Insights) to visualize these outcomes.
“With the methods our team has developed, we can apply the ‘3-30-300’ benchmark to any city worldwide,” said Dirk Voets, Senior Advisor Geospatial at Cobra Groeninzicht.
