July 29: Urban forests can significantly reduce temperatures during extreme heat waves, with broadleaf and mixed forests providing the strongest cooling effect according to a new study by South Korea National Institute of Forest Science.
The research, based on continuous monitoring of temperature and humidity across different urban environments in Seoul, found that forests can lower daytime temperatures by up to 1.8 degrees Celsius compared to densely built-up city areas.
Among different forest types, broadleaf and mixed forests containing both deciduous and coniferous trees were the most effective, reducing temperatures by 1.5 to 1.8 degrees Celsius. Coniferous forests provided a smaller cooling effect of about 1.2 degrees Celsius.
Researchers attributed the cooling to dense tree canopies that block direct sunlight and evapotranspiration a natural process in which trees release water vapour, absorbing heat from the surrounding air and creating a cooler microclimate.
The cooling effect also continued after sunset. Urban forests remained 1.3 to 1.6 degrees Celsius cooler than surrounding built up areas at night, helping reduce the impact of tropical nights, when temperatures remain uncomfortably high. Unlike concrete and asphalt, forests store less heat during the day and release less thermal energy after dark.
The study highlights the importance of diverse, multilayered forests as essential urban infrastructure for climate adaptation. Researchers recommend that city planners prioritise broadleaf and mixed forest vegetation in parks and green spaces to improve heat resilience enhance public health and make cities more livable as climate change increases the frequency and intensity of heat waves.