We all can feel the coolness when we walk in shady areas under trees on hot days. We also know how unpleasant it is to walk on hot sidewalks next to hot buildings made of brick or concrete. Did you know that the temperature difference that we feel can also affect our health?
A news story in Euronews explains a new study about trees and heat-related deaths in cities and urban areas. The study found that just 30% more trees could have prevented 1.1 million heat-related deaths worldwide in the 20 years between 2000-2019. The researchers studied how much the trees cooled cities, and how much that cooling reduced deaths.
In North America from 2000-2019, 110,000 deaths were heat-related. Increasing trees and other vegetation in cities and urban areas by 10% could have prevented 58,000 deaths (53% of heat-related deaths). Increasing trees by 20% would prevent 65,000 deaths (59% of heat-related deaths). Increasing trees by 30% would prevent 69,000 deaths (63% of heat-related deaths). (This is from Table 1 in the study.)
Worldwide, 3 million of 127 million deaths (2.48%) are attributed to heat exposure. Increasing vegetation (trees and more) by 10% could prevent 860,000 deaths (27% of heat-related deaths). Increasing trees by 20% could prevent 1.02 million deaths. Increasing trees by 30% could prevent 1.16 million deaths (37% of heat-related deaths).
The Euronews story explains how trees help – they shade surfaces (the streets and buildings don’t get so hot), they deflect radiation from the sun (and also absorb some for photosynthesis), and they increase evaporation from the trees which makes the air move more.
This study included 830 cities and urban areas in 53 countries. Because it is so large, the numbers in the results are very strong. All of the global and North American numbers were what scientists call statistically significant, meaning they are not due to change.
Many studies show that increased heat doesn’t only cause heat stroke and other heat illnesses. Increased heat also causes more premature births, and more problems for people with lung disease or heart conditions. Planting more trees, grass, and bushes can keep cities cooler, and keep us healthier.
Read the news story in Euronews here.
Read the scientific study in the Lancet here.
03/26/2026 AKMB
