City sidewalks are no place for giant trees

As Hanoi’s residents resumed their daily routines, they were met with the sight of fallen trees everywhere, a stark reminder of the city’s cherished greenery. However, these fallen trees also became a deadly hazard, contributing to several fatalities.

The tragic incidents have reignited the debate on whether to preserve large, aging trees in urban areas or replace them with smaller, more manageable species. This discussion is not just about aesthetics or tradition but about the safety of the people who live, work, and travel through these tree-lined streets.

The preservation of large, old trees in urban environments is rare globally. In most countries, trees towering over a dozen meters are usually found in parks or rural areas, not along busy city sidewalks. As these trees grow, their expansive canopies often shade nearby houses more than the streets they were planted to protect. Moreover, their extensive root systems can cause significant damage to infrastructure, leading to costly maintenance.

In Hanoi and other cities, the focus should shift towards planting trees that are shorter, with flexible branches and wide canopies that provide ample shade without posing significant risks. These trees would not only enhance the cityscape but also ensure the safety of pedestrians and motorists alike.

A man climbs over the trunk of a tree uprooted by typhoon Yagi as he walks around the Sword Lake in Hanoi, Sept. 13, 2024. Photo by VnExpress

Public safety must take precedence in urban planning, including decisions about tree management.

Singapore’s approach offers a compelling example. The National Parks Board routinely inspects older or larger trees, removing any that do not meet safety standards. New trees are then planted to maintain the city’s greenery. Trees taller than 20 meters are typically reserved for parks or suburban areas, where they have the space to develop robust root systems.

In urban settings, large trees should be confined to parks and botanical gardens, where their size poses less risk to people. On sidewalks, trees with lower heights and wider canopies would be more appropriate, providing shade while minimizing the dangers associated with falling branches.

As typhoon season approaches, it is crucial to implement measures that protect both the city’s greenery and its residents. Routine inspections by experts can identify early signs of danger, such as decaying trunks or diseased branches. Modern technologies like Virtual Tree Assessment (VTA) and ultrasound can aid in these assessments.

Trimming trees to remove weak branches and reduce wind resistance is another vital step. Ensuring that tree roots are healthy and have sufficient space for growth can prevent uprooting. For trees of high value, additional supports like cables or columns may be necessary to enhance their stability during storms.

Moreover, trees must be well-nourished and protected from pests, as healthy trees are more likely to withstand extreme weather conditions.

The loss of trees during typhoon Yagi is undoubtedly a source of sorrow for many in Hanoi. However, it also presents an opportunity to plant new, more suitable trees. Urban trees should be chosen for their strong roots, resilience to wind, and resistance to snapping. Two species particularly well-suited for Vietnamese sidewalks are the monkey pod tree (Samanea saman) and the tembusu tree (Fagraea fragrans). Both thrive in tropical climates, require minimal care, and offer significant greenery.

As the climate becomes increasingly unpredictable, urban greenery planning must strike a balance between preserving nature and ensuring human safety. Ultimately, safety should be the guiding principle in any decisions regarding the trees that line our city streets.

*Trinh Phuong Quan is an architect with a master’s degree at Stanford University in the U.S.