A new IIASA-led study finds that expanding street green space can reduce urban heat stress in cities worldwide, but even ambitious greening efforts are unlikely to offset a significant share of the additional heat expected under climate change. Instead, the research shows that street greenery should be part of a broader portfolio of urban adaptation measures.

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 published in Environmental Research Letters, 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.