Street green space can help cool cities, but it will not be enough on its own

Cities are on the front line of climate change, with rising temperatures and heat stress posing growing risks to health, productivity, and livability. Street green space, such as trees and vegetation along streets, is often promoted as a practical nature-based solution because it can provide shade, cooling, and other positive benefits, for example, improving the mental health of citizens. Yet, evidence on how much cooling street greenery can deliver, to which extent the amount of vegetation can be increased, and how much cooling can be expected in future climates, has remained limited, particularly when taking a global view across very different urban forms and climate zones.

In the new study, a team of researchers from IIASA and VITO Belgium combined high-resolution street greenery data with 100-meter urban microclimate model outputs for 133 cities worldwide, providing a neighborhood-scale assessment with global coverage. Rather than relying on satellite-based surface temperature alone, the team assessed how street green space relates to air temperature and wet-bulb globe temperature – a measure that captures heat stress more appropriately than temperature alone, because it accounts for humidity, wind, and radiation.

The results show that street greenery can help reduce heat stress in cities, but its benefits are uneven and depend strongly on local conditions. Generally, the cooling effect is stronger in tropical and continental climates, while it is generally weaker in dry and temperate climates. The cooling potential is also shaped by urban form: the most consistent benefits tend to appear in open and low-rise neighborhoods, as well as in large low-rise areas, where greenery has more room to interact with the local microclimate.

“In practical terms, this means that greener streets can make a measurable difference, but not everywhere to the same degree,” explains Steffen Lohrey, co-lead author of the study, former guest researcher at IIASA, and Promovendus at the Institute for Environmental Studies, VU University Amsterdam.

Also, upper feasible levels of street greenery expansion differ across climates, with drier or continental regions generally facing tighter limits than tropical or temperate ones. This means that the places with the greatest need for cooling are not always the places where large expansions of greenery are easiest to achieve.

The authors then explored what these findings could mean by 2050 under different climate and urban greening scenarios. They found that, under a “current policies” climate scenario, expanding street greenery at levels that are ambitious but still realistic for each city, could offset about 3% to 11% of the expected increase in maximum wet-bulb globe temperature. Under a high-emissions scenario, this cooling effect is smaller, reducing the increase by about 2% to 7%, depending on local conditions. The authors also warn that if street greenery declines, either due to lack of action or because plants are stressed by extreme weather conditions, urban heat could become even more severe.

“For policymakers and city planners, our findings suggest that investing in street greenery is worthwhile, but that it is not a substitute for broader action, which is chiefly increasing efforts to reduce greenhouse gas emissions. On the adaptation side, greening needs to be integrated with other measures, such as improved building materials, and better urban design”, notes Niels Souverijns, Senior Climate Scientist at VITO and a co-author of the article.

The study also highlights the importance of maintaining existing vegetation and paying attention to where greening occurs within cities, so that adaptation does not deepen existing inequalities in heat exposure.

“By providing globally comparable evidence across 133 cities, the study helps clarify both the promise and the limits of street green space as an urban climate adaptation strategy. It shows that greener streets can play an important role in reducing heat stress, but that safeguarding urban populations in a warming world will require more comprehensive and context-specific responses,” concludes Giacomo Falchetta, co-lead author of the study and a research scholar in the IIASA Energy, Climate, and Environment Program.

Reference 
Falchetta, G., Lohrey, S., Souverijns, N., Lauwaet, D., Schleussner, C.-F., and Niamir, L. (2026). Street green space is relevant but not sufficient for adapting to growing urban heat in world cities. Environmental Research Letters DOI: 10.1088/1748-9326/ae5c20