A landmark global study has revealed that increasing vegetation in cities by just 30% could have prevented over one-third of all heat-related deaths between 2000 and 2019 potentially saving 1.16 million lives worldwide. The research led by Monash University Professor Yuming Guo and published in The Lancet Planetary Health provides the most detailed modeling to date of how urban greenery can cool cities and save lives.
Greener Cities, Cooler Summers, Fewer Deaths
The study analyzed data from 11,534 urban areas, showing that a 10%, 20%, and 30% increase in vegetation would have lowered the global population-weighted warm-season mean temperature by 0.08°C, 0.14°C, and 0.19°C, respectively. These seemingly small changes in temperature could have reduced heat-related deaths by:
- 0.86 million with 10% more greenery
- 1.02 million with 20% more
- 1.16 million with a 30% increase
- This corresponds to a 27.16%, 32.22%, and 36.66% reduction in global heat-related mortality.
Heat Kills – But Greenness Heals
From 2000 to 2019 heat exposure was responsible for approximately 0.5 million deaths per year accounting for nearly 1% of global mortality. Urban areas, with their concrete landscapes and limited shade, bear the brunt of extreme heat especially in warmer and lower-income regions.
Vegetation helps reduce this deadly burden in multiple ways. Trees and plants:
- Provide shade and reduce sun exposure
- Cool the air through evapotranspiration
- Deflect radiation and absorb pollutants
These effects lower the risk of heat-related illnesses and death particularly among vulnerable populations such as the elderly and those with pre-existing health conditions.
Where Greening Saves the Most Lives
The regions that could have benefitted most from increased urban greenery include:
- Asia: 527,989 lives saved
- Europe: 396,955 lives
- Latin America & the Caribbean: 123,085 lives
- North America: 69,306 lives
- Africa: 35,853 lives
- Australia & New Zealand: 2,759 lives
- Oceania (excluding Australia/NZ): 2,733 lives
The biggest reductions in heat-related mortality were found in Southern Asia, Eastern Europe and Eastern Asia regions with both large urban populations and high exposure to extreme heat.
Why This Study Matters Now
This is the first global modeling study to quantify both the cooling and modifying effects of vegetation on heat-related deaths. These findings indicate that preserving and expanding greenness might be potential strategies to lower temperature and mitigate the health impacts of heat exposure.
With climate change accelerating, estimates show that heat-related deaths could rise dramatically reaching up to 16.7% of all deaths in Southeast Asia by the end of the century under extreme warming scenarios. Greening urban areas offers a cost-effective and nature-based solution to this looming crisis.
More Than Just Temperature: Social and Health Benefits
Beyond cooling, greenness may offer additional health advantages by:
- Improving mental health and well-being
- Encouraging physical activity
- Reducing isolation through social interaction
- Filtering air pollutants that worsen respiratory illness
- These combined effects make urban greening not just a climate solution, but a broader public health intervention.
Looking Forward: Greenness as Urban Survival Strategy
The researchers used data from the Multi-Country Multi-City (MCC) Collaborative Research Network, integrating mortality and weather data from 830 locations in 53 countries. Vegetation levels were measured using NASA’s Enhanced Vegetation Index (EVI) allowing the team to track green cover across thousands of urban centres.
Defined as areas with at least 1,500 people per square kilometer and a total population of over 50,000, these urban zones are home to billions and growing rapidly.
As cities expand, integrating green infrastructure parks, tree-lined streets, green roofs could make the difference between life and death for millions in a warming world.
With temperatures rising and urban populations swelling the time to act is now.