A recent study shows that urban tree canopies play a crucial role in combating the “urban heat island” (UHI) effect. They reduced the temperature gap between cities and rural areas by almost half.
Trees provide shade and cool the air through a process called transpiration, lowering the air temperature in summer by a population-weighted average of 0.15°C on average, as reported in research published in the journal Nature Communications. However, this extensive research highlights nature’s limitations, and although increasing urban forests remains important for public health, scientists point out that trees alone cannot counter the massive temperature rises caused by fossil fuel emissions around the world.
With cities likely to warm by up to 2.4°C by 2050, it is clear that urban forests need to be combined with strong efforts to reduce carbon emissions.
Scientists reveal how trees naturally reduce dangerous heat levels in the city
According to research published in the journal Nature Communications, the study used satellite data and climate modeling across 8,919 large urban areas to measure the cooling power of green infrastructure. It found that trees are responsible for mitigating approximately 41 percent to 49 percent of the maximum potential Universal Health Coverage (UHI).
Cooling occurs through two primary mechanisms: shading, which prevents sunlight from reaching sidewalks and buildings and heating them, and evaporation, where trees release moisture into the air, acting as a natural air conditioner. Without today’s urban tree cover, the heat trapped in cities would be twice what it is today.
The tree shortage represents a growing public health crisis for poor people
Research reveals a stark difference in who benefits from natural cooling.
He points to a “cold divide” between rich and poor countries. Nearly 40 percent of high-income cities in richer countries benefit significantly from tree canopies, while less than 9 percent of cities in poorer countries have enough trees to make a difference. In many rapidly growing cities in the Global South, such as Dakar and Port-au-Prince, there is almost no benefit to cooling.
This situation puts the most vulnerable people at greater risk of heat-related health problems.
Why can’t even the maximum number of trees stop Global warming
The researchers explored a scenario in which cities achieve maximum tree cover to see if this approach could address the climate crisis. Their findings showed that even with each city maximally expanding its tree canopy, this would only result in an additional 0.3°C of cooling. When compared to the expected global temperature rise of 1.5°C to 2.4°C by 2050, this is not enough. The study, published in the journal Nature Communications, suggests that although trees play a vital role in making urban areas more livable, they provide only limited relief from the larger problem of climate change, which is largely caused by greenhouse gas emissions.
Implications of using green infrastructure to protect high-risk areas
The study suggests that future urban planning should focus on “strategic planting” to help protect high-risk neighborhoods. Trees cool the surrounding area, so placing more of them in low-income neighborhoods with fewer trees can save lives during heat waves. But there’s a problem: For these trees to thrive and cool effectively, global carbon emissions must be reduced. Extreme heat and drought threaten the very trees designated for protection, making it essential to address climate change simultaneously.
