As global temperatures continue to increase and regional climates continue to shift, the ecological communities in these impacted regions are starting to respond in kind. In particular, researchers have observed noteworthy alterations in the cyclic development and flowering (or phenology) of perennially flowering plants within the past few decades alone. More apparent shifts in phenology tend to be visible in culturally significant plants, such as cherry blossoms, which have generated an entire history and culture of blossom viewing seasons in Japan and abroad. As cherry blossom viewing seasons begin to shift with each coming year, researchers are starting to become concerned about the impact that climate change is having on an integral facet of Japanese culture.
Higher Temperatures Lead to Earlier Blooming Times
In order to understand how perennially blooming plants respond to climate change, researchers can often reference extensive records of blooming seasons, temperatures, and climate trends. While some vital information has been provided by measurements taken by the Japan Meteorological Agency (JMA), other essential data has been found in the rich cultural history of Japan itself. The popularity and cultural significance of these pink and white flowering trees means that cherry blossoms have always remained a hot topic, with records of blooming times and bloom quality abound in historical royal documents and newspapers from culturally rich cities like Kyoto. Historical and cultural documents, as well as diaries ranging from the 9th to 14th centuries, have provided valuable information for climate researchers, who are able to use this data to perform a climatic reconstruction of cherry blossoms in Japan.
After looking at around 1200 years of Japanese cherry blossom history, researchers have noticed that cherry blossoms are now flowering progressively earlier than they ever did before. According to the data, a trend in earlier blossom time starts to become noticeable just around the year 1830, with more prominent early flowering happening during the 1980’s and beyond. Within the past 50 years alone, cherry blossom plants have started to flower an average of 1 week earlier than usual. Researchers suspect this trend is linked to overall trends in climate change, especially since cherry blossom flowering times are primarily influenced by temperature. Most cherry blossom breeds tend to flower in the springtime, just as colder temperatures start to transition into warmer temperatures. This response to temperature may very well be an evolutionary trait, which happens to promote plant development and prevent frost damage to the fragile flowers. Evidence of earlier blooming times may therefore indicate that temperatures are starting to increase at earlier and earlier points in the year.
While a large majority of the phenological shifts are linked to regional climatic warming, researchers estimate that at least one third of the cherry blossom changes observed in Kyoto have been linked to urbanization alone. Indeed, over 100 JMA weather stations across the country have observed an average increase in temperature over the past 50 years, with greater increases found in urban areas instead of rural areas. Current climate change estimates project that temperatures will only continue to rise in the near future, due largely to global warming and anthropogenic urbanization in Japan. In addition to its overall environmental impact, many people also worry that climate change will ultimately harm the future of cherry blossom viewing seasons and their vital role in Japanese culture.
New Climate, New Flowers
In response to these concerning changes, researchers at the RIKEN Nishina Center for Accelerated-Based Science have been hard at work on a horticultural solution to combat earlier and shorter cherry blossom seasons. Back in the early 2000’s, researchers began work on the development of more durable varieties of cherry blossoms, an effort which ultimately led to the popular Nishina Otome breed. Named after Yoshio Nishina, the father of RIKEN’s accelerator, this new breed is colloquially known as the “perpetual cherry blossom”. While conventional cherry blossoms need to undergo a cold spell before they bloom in the warmer days of early spring, Nishina Otome cherry blossoms can flower entirely without this cold period, resulting in blooms that typically happen twice a year.
In order to generate these new breeds, researchers utilize a unique horticultural method called the heavy-ion-beam breeding technique. Perhaps the most unique element of this technique is the use of accelerators, such as RIKEN’s Ring Cyclotron, to generate heavy ion beams. Prior research in biological studies has shown that heavy ion beam irradiation can cause a double strand break in DNA, ultimately resulting in an induced deletion mutation. By applying these ion beams to plants, such as cherry blossoms, new mutant strains with potentially different properties are generated. Mutant strains that exhibit favorable qualities, such as altered color or blossoming characteristics, are then grafted and cultivated to create a new breed of cherry blossoms.
One of the earliest varieties of cherry blossoms to be generated via this novel technique was the Nishina Zao, a pale-yellow cherry blossom that was created in collaboration with JFC Ishii Farm in Japan’s Yamagata Prefecture. Since the development of the perpetual Otome blossom, researchers have experimented with even more blossom varieties, such as the Nishina Haruka and Nishina Komachi breeds. Ultimately, the production of these new cherry blossom breeds may help to counteract the phenological shifts of climate change and aid in the preservation of the historic and cultural traditions of cherry blossom viewing in Japanese culture. The methods used to achieve this preservation also hold utility beyond the production of cherry blossoms alone. Heavy-ion-breeding technology is starting to emerge as a unique Japanese horticultural technique, which can be used to develop new varieties of popular flowers and essential crops. As the technology grows and develops on the international market, many people predict that it will bring significant environmental and economic advantages for agricultural industries around the world.
- Primack, R. B., Higuchi, H., & Miller-Rushing, A. J. (2009). The impact of climate change on cherry trees and other species in Japan. Biological Conservation, 142(9), 1943-1949.
- Primack, R., & Higuchi, H. (2007). Climate change and cherry tree blossom festivals in Japan. Arnoldia, 65(2), 14-22.
- Aono, Y., & Saito, S. (2010). Clarifying springtime temperature reconstructions of the medieval period by gap-filling the cherry blossom phenological data series at Kyoto, Japan. International journal of biometeorology, 54(2), 211-219.
- RIKEN’s Nishina Otome in full bloom
- New cherry blossom tree blooms in all four seasons | RIKEN press release
- Invention of heavy-ion-beam breeding technique established in Japan | RIKEN Institute’s Applied Research