Asia-Pacific

Tokyo’s Vanishing Trees Leave City More Exposed to Extreme Heat

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By Alex Chen/Shir Bashi/Eric Gau

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Tokyo is losing tree cover as summers grow hotter, raising concerns about the risks of extreme heat. Researchers say the Japanese capital has less than half the tree canopy cover of cities such as New York and London, with coverage shrinking by a fifth over a decade. Residents and advocates are measuring temperatures to show how trees provide shade and lower local heat. Experts warn that heavily pruned trees offer less protection, while disappearing private gardens are contributing to the loss of greenery. Although authorities cite safety concerns to justify pruning, researchers say Tokyo needs clear targets and policies to expand its tree canopy.

Residents and tourists alike seek respite from the heat as Japan’s capital swelters under the sun. Scenes like these are becoming more common around Tokyo as temperatures hit record highs. Last summer was the hottest ever... and nearly 120 people have died of heat-related illness this year.

FUJII EIJIRO, PROFESSOR EMERITUS CHIBA UNIVERSITY:
"There's no time to waste. In reality, deaths from heatstroke are rapidly increasing in Japan. The annual number now exceeds 1,000."

The city has rolled out solutions to keep people cool, but some residents have zeroed in on a particular issue... Tokyo has a lot less greenery than other world cities. In one Tokyo neighborhood, residents have been hitting the streets to measure and understand how greenery affects temperatures. They say the problem is not just a lack of trees.

MORIMOTO KAORU, ADVOCACY GROUP CO-FOUNDER:
"We measured the shade under trees with large canopies and under trees that had been more heavily pruned and offered less shade. There was about a 3‑degree difference, so today we also learned that the size of the tree canopy affects the temperature."

Academics agree that Tokyo has a tree problem. University researchers say the city has less than half the tree canopy cover of other metropolises like New York and London. And what leafy cover it has is rapidly shrinking. Tokyo’s coverage shrank by a fifth during a 10-year-study – by an area over three times the size of New York’s Central Park.

SHIRAISHI KINYA, RESEARCHER UNIVERSITY OF TOKYO:
"Unfortunately, Tokyo doesn't have a canopy cover target yet. So I think this is a big difference between those major cities in the world and Tokyo."

Observers say the green retreat is due to disappearing private gardens... and overzealous pruning of what trees remain. Authorities defend the cuts, saying trees can obstruct traffic lights and can fall during typhoons.

As global temperatures rise, cities like Tokyo will need to find a way to keep cool. Concerned citizens say local politicians are paying more attention to foliage now... but there are no clear targets.

FUJII EIJIRO, PROFESSOR EMERITUS CHIBA UNIVERSITY:
"Therefore, in the future, we'll be in a critical situation. Unless we promptly make efforts to increase canopy cover and shift our policies, we'll run out of time."

Local advocates might have planted a seed. But Tokyo – and its residents – are far from out of the woods.

Alex Chen, Shir Bashi and Eric Gau for TaiwanPlus