Cherry blossoms are blooming early from Tokyo to Washington

By Shoko Oda, Zahra Hirji and Brian K Sullivan

(Bloomberg) — Iconic cherry trees in Japan and the US are blossoming earlier as climate change brings warmer temperatures, upending a fixture of the spring calendar in major cities.

No country is more associated with blossoming cherry trees, or sakura, than Japan, and tourists from overseas often try to time their visits to see the delicate pink petals. The average date at which they start to bloom has moved up 1.2 days per decade since 1953, said Daisuke Sasano, a climate risk management officer at the Japan Meteorological Agency.

Between 1961 and 1990, cherry trees in Tokyo started blooming on 29 March on average. Between 1991 and 2020 that date moved up to 24 March, Sasano said.

Last year, the sakura in Tokyo were the first to bloom in all of Japan, on 14 March. That was unusual, since they typically bloom first in the southern part of the country and later in the north along what the JMA calls the “cherry blossom front.”

“The fact that Tokyo recorded the earliest start date is due to global warming, compounded with urbanisation,” Sasano said, referring to the urban heat island effect, which causes cities to trap heat. Tokyo has warmed 3˚C over the past century.

Another forecaster, the Japan Weather Association, predicts Tokyo’s cherry blossoms this year will start blooming on 21 March.

The world saw warmer-than-normal temperatures this winter, with January 2024 being the hottest January on record. There’s a correlation between warmer temperatures and earlier starts to springtime blooms, said Theresa Crimmins, director of the USA National Phenology Network, which tracks seasonal changes.

“Spring is most definitely starting earlier than when you were a kid – there is no doubt about that,” said Crimmins, who is also an associate professor in phenology at the University of Arizona. “Many, many studies show clear trends toward warmer temperatures and earlier starts to springtime activity over the longer term.”

Sakura flowers are greeted with much excitement in Japan. People gather in groups to have picnics, a centuries-old custom known as hanami. A study by an academic at Kansai University estimated the economic impact of the flowers last year to be 616 billion yen (US$4.1 billion). Private weather data providers are also making a business out of predicting when the flowers will bloom.

If rising temperatures cause the flowers to bloom earlier or shorten their full-bloom phase, cities that capitalise on the cherry blossoms could be impacted, said Sasano. “That results in a shorter time available for enjoying the cherry blossoms, which may impact tourist destinations where the flowers are considered as important resources.”

Yet earlier blooming isn’t a given as winter temperatures rise. Cherry trees need exposure to a “sufficient chill” to get them to wake up when spring warmth arrives, Crimmins said. “If we start to experience warmer winters, it is possible that the trees will not achieve their necessary chill. When this happens, we tend to see delayed flowering, reduced flower and fruit production, and generally ‘confused’ trees,” she said in an email. Although not a risk this year, it could be in the future.

Thousands of miles from Tokyo, in Washington, DC, nearly 4,000 cherry trees – the oldest of them gifted by Japan and planted in the US capital in 1912 – are also a major tourist attraction. For roughly a month each spring the city holds the National Cherry Blossom Festival, which is “an economic engine,” the DC Chamber of Commerce said in an email. Each year, the festival draws an estimated 1.5 million people from across the globe and generates more than US$100 million in visitor spending.

The Yoshino-variety cherry trees planted around the Tidal Basin near Washington’s National Mall are the focal point for most visitors. The US National Park Service tracks when these trees reach “peak bloom,” or when 70% of the blossoms are in full bloom.

Peak bloom has shifted earlier – about seven days since 1921, according to government data. Based on roughly a century of data, the average peak bloom date is 4 April. This year, the Park Service predicts peak bloom will arrive particularly early, between 23 March and 26 March.

On top of the trees feeling the brunt of warmer spring weather, rising water levels in the adjacent Potomac River – an effect of climate change – combined with crumbling sea walls and subsidence have led to the roots of some being inundated with water. Soon the iconic cherry trees will be impacted by a climate resilience project. The Park Service will remove more than 150 of them, and roughly the same number of other kinds of trees, from around the Tidal Basin and West Potomac Park in a multiyear effort to fix the sea walls. The agency is planning to plant 455 new trees, including 274 cherry trees, when it’s finished.

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