Cherry Blossom Legacy Lives On: 1,200-Year Climate Record Secured After Scientist's Death
In a poignant turn of events, a 1,200-year record of cherry blossom flowering dates in Japan, meticulously compiled by the late Prof Yasuyuki Aono, will continue despite his passing. This dataset, one of the world's longest climate records tracking a seasonal occurrence, has gained renewed attention as a new researcher steps forward to carry on the vital work.
A Lifelong Dedication to Climate Science
Prof Yasuyuki Aono of Osaka Metropolitan University dedicated his career to gathering data on the spring flowering dates of cherry trees in Japan. Using sources dating as far back as the 9th century, he revealed that cherry tree flowerings have occurred progressively earlier in recent decades, serving as a now-famous marker of climate change. Peak blossom day is earlier in the year due to higher temperatures, with his research highlighting significant shifts.
Last April, Aono posted a photo to social media of his spreadsheet, having just completed the 2025 entry. He recorded "4 [April]" as the peak flowering date for the mountain cherry, or Prunus jamasakura, the specific species he tracked. Below this, the next row was already marked "2026," but Aono never got to fill it in. He died on 5 August last year, according to former colleagues.
Emotional Discovery and Urgent Search
Tuna Acisu, a data scientist at Our World in Data, an online platform that publishes a chart based on Aono's cherry tree data, expressed deep emotion upon seeing the spreadsheet. "You can very much see that he planned to continue," she said. "That made me a little bit emotional." In January, Acisu and colleagues realized something was amiss when Aono's university web page went inactive. They soon learned of his death and that no other researcher or institution had emerged to continue the observations, leaving the 2026 data unfilled as spring arrived.
Fearing the loss of this invaluable climate record, Acisu launched a search last week to find a new cherry blossom observer. The response was overwhelming, with dozens of messages pouring in. "It's really great to know that the dataset is being continued," she said, expressing gratitude to the new researcher. "I feel very relieved." A researcher in Japan has now offered to make formal observations of the mountain cherry's spring flowerings, consulting the same sources as Aono to determine this year's peak bloom date.
Critical Importance of Specific Data
What makes Aono's work so significant is its specificity. He tracked the mountain cherry in the same location: Arashiyama, Kyoto. While other projects monitor cherry tree flowerings in Japan, such as the Japan Weather Association's focus on the Somei-yoshino cherry, Aono's dataset spans over 1,200 years for this particular species. This longevity provides unparalleled insights into climate patterns.
Scientists have found evidence of climate change in various sources, including tree rings and historical records, but Aono's meticulous approach stands out. He learned old forms of Japanese to read 9th-century records, scouring dusty archives for references to cherry blossom festivals in Kyoto to calculate flowering dates. The earliest record he found dated to 812, with some years missing but the series largely intact.
Academic and Environmental Impact
Toshio Katsuki, a dendrologist at the Forestry and Forest Products Research Institute, emphasized the academic value of continuing this record. "Aono's work on the mountain cherry was extremely important," he said, noting that efforts to record the same species' spring flowering dates would be academically valuable. Richard Primack, a professor of biology at Boston University who met Aono in 2006, recalled his dedication. "It was really quite an amazing experience," Primack said. "You just realize how dedicated an individual he was."
In a recent paper, Primack and Katsuki described how climate change affects cherry blossoms in southern Japan, with milder winters causing Somei-yoshino cherries to have a bedraggled look rather than a full display. This underscores the broader environmental implications of Aono's work, as cherry blossoms are not only cultural icons but also critical indicators of our changing planet.
Looking Ahead
With the new researcher set to continue the observations, the 1,200-year cherry blossom record will live on, preserving a legacy of climate science. This ensures that future generations can track the impacts of climate change through the delicate timing of spring blooms, honoring Prof Aono's lifelong commitment to understanding our world.
