Cherry Blossom Record to Endure Despite Scientist's Passing
After more than 1,200 years of meticulous documentation, the iconic cherry blossom record in Japan will continue, despite the recent death of the dedicated scientist who maintained it. Prof Yasuyuki Aono of Osaka Metropolitan University dedicated his career to tracking the spring flowering dates of cherry trees, creating one of the world's longest climate records for a seasonal event.
A Legacy of Climate Insights
Using historical sources dating back to the 9th century, Aono revealed that cherry tree flowerings have been occurring progressively earlier in recent decades, serving as a stark marker of climate change. Higher temperatures have caused peak blossom days to shift earlier in the year, with the 2021 and 2023 dates being the earliest in the entire mountain cherry record, occurring on the 85th and 84th days of those years, respectively.
In his final months, Aono continued his work, posting a photo to social media in April last year of his spreadsheet with the 2025 entry completed, recording "4 [April]" as the peak flowering date for the mountain cherry, or Prunus jamasakura. The next row was marked "2026," but he never filled it in, passing away on 5 August last year.
Search for a Successor
Concerns arose when Aono's university web page became inactive in January, leading Tuna Acisu, a data scientist at Our World in Data, to launch a search for someone to continue the record. "You can very much see that he planned to continue," Acisu said, expressing emotion over the unfinished spreadsheet. "That made me a little bit emotional."
Last week, a researcher in Japan stepped forward, offering to make formal observations of the mountain cherry's spring flowerings in the same location: Arashiyama, Kyoto. The researcher, who asked to remain anonymous until arrangements are finalised, is consulting the same historical sources as Aono to determine this year's peak bloom date.
Importance of the Dataset
Acisu emphasised the significance of Aono's work, noting that while other projects monitor cherry tree flowerings in Japan, such as the Japan Weather Association tracking the Somei-yoshino cherry, the mountain cherry dataset spans over 1,200 years, making it uniquely valuable. "It's really great to know that the dataset is being continued," she said, relieved by the new researcher's involvement.
Toshio Katsuki, a dendrologist at the Forestry and Forest Products Research Institute, described Aono's work as "extremely important," adding that continuing the record would be academically valuable. Richard Primack, a professor of biology at Boston University, recalled meeting Aono in 2006, where Aono shared how he learned old forms of Japanese to read historical archives and calculate flowering dates from references to cherry blossom festivals in Kyoto.
Broader Climate Implications
Scientists have linked climate change to various natural indicators, including tree rings and seabed sediments. In a recent paper, Primack and Katsuki highlighted how milder winters are affecting Somei-yoshino cherry flowerings in southern Japan, causing buds to fall off without opening, resulting in a less vibrant display. This underscores the broader environmental shifts captured by Aono's lifelong dedication.
As spring arrives, the continuation of this historic record ensures that Aono's legacy will endure, providing ongoing insights into the impacts of climate change on Japan's cherished cherry blossoms.
