The best tree for securing shade is the London planetree...

Creating urban "forest canopies" to combat heatwaves during a climate crisis is absolutely the most effective approach. However, Korean cities are experiencing an unfortunate trend where shade trees like poplars are being replaced by less beneficial varieties. The research from the Forest Science Institute reveals that shade trees create cooling effects through varying factors, primarily stem size, leaf count, canopy shape, and evaporation efficiency.

Among these, the poplar (Platanus) stands out as the best for cooling. A 2014 study from Seoul National University found that when mixed with large and small-sized poplars, poplars reduced temperatures by 2.57 degrees Celsius. Following this, elm and sycamore trees reduced temperatures by 2 degrees Celsius and 1.84 degrees Celsius respectively, while willow trees lowered temperatures by 1.35 degrees Celsius.

Poplars, known for their large canopies and numerous leaves, also excel in reducing fine particulate matter. According to the Forest Science Institute, poplars, elm, and sycamore trees are the top three for fine particulate matter reduction due to their wide tree crowns, numerous leaves, and developed leaf surface structures. Poplars are the most widely planted urban tree globally, but they are becoming scarce in Korean streets.

The Forest Service reported that poplars have decreased annually from 2021 to 2025, with 33,669 trees lost. The city's urban forestry department explained that poplars were most commonly planted during the 1960s and 1970s, and now their age and structural weaknesses make them more prone to falling. Professor Jo Kyung-hel from Seoul National University University countered the claim that poplars are easily uprooted, stating that they often cause more damage to narrow sidewalks rather than falling down.

However, he emphasized that during heatwaves, poplars should be reconsidered as the primary urban tree. Other recommended urban trees include sycamore, which follows poplars in effectiveness, followed by Chinese dogwood and Chinese tulip tree. Currently, the most commonly planted trees in Korea are poplars and cherry blossoms. While these two trees beautify the city in spring with their blossoms, they are not ideal for creating tree canopies.

Seoul's city planner, Hyun Seong-hyun, noted that the city's recent planting decisions have been influenced by the preferences of citizens, with popular flowering trees like poplar and cherry blossom being favored. He added that climate crisis and heatwaves are not yet significant factors in tree selection. To grow trees, sufficient space is needed, but Korean sidewalks are too narrow for proper tree growth.

Professor Jo Kyung-hel explained that on sidewalks typically 3 meters wide or less, trees cannot be properly grown, and underground utilities also limit root development. He stressed that to create proper urban canopies, sidewalks must be widened, and underground space must be expanded. During climate crises, reducing the number of vehicles emitting carbon and heat through cutting down less effective trees and increasing sidewalks is crucial.