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Mr. Toemon Sano is the 16th owner of Uetoh Zoen (Uetoh Landscape Gardening), which was founded in the 3rd year of Tempo (1832). His family descends from a gardener who took care of the imperial palace garden at the Ninnaji temple domain in Omuro, Kyoto. His grandfather, as a cherry blossom guardian, began a family tradition of traveling around the country to see cherry trees.
In the old days, cherry blossoms were used as a yardstick for rice planting and fishing. That shows how close cherry trees were to people’s lives. Having interacted with cherry trees for a long time, I feel it is us human beings that need to change our lives and restore harmony with nature.
As a cherry blossom guardian
It was in my grandfather’s days that my family started to take care of cherry trees. They are living things so they eventually wither and die. There are several well-known cherry trees known for their beautiful blossoms around the country, but they too will eventually die. My grandfather wanted to ensure that those splendid trees would remain and tried to make successors for them. Whenever he heard about a large or splendid cherry tree somewhere around the country, he would go to see it and took grafts and grew saplings. I heard that he went even to the Kuril Islands and Sakhalin. So it was tremendous work. In the end, he raised 100,000 saplings.
Following in his footsteps, I learned about the bounties of nature unconsciously. It was after my father died that I started to work earnestly with cherry trees. It is possible, to a degree, for us to make flowers bloom on trees that already have buds. But unless the buds come out, there is nothing one can do. It was after I started to interact with cherry trees that I began to be conscious about the life of trees and how to let them live.
Cherry blossoms differ according to the weather
The number and color of cherry blossoms differ from year to year. This is mostly due to the weather of the preceding summer.
For cherry trees, summer is a season of growth. The trees absorb nutrients through the roots and carry them to the branches to promote photosynthesis. When this process settles down, the nutrients are sent to the trunk. It is after the Buddhist Bon season in August (the hottest season in midsummer), that the trunk begins to grow in earnest. Around this time, the buds that will become next spring’s blossoms begin to form.
We call them “zero buds.” In other words, the preparation for blossoms has begun.
The physiology of cherry trees is that these zero buds accumulate energy during the winter time. At some point in the spring, they suddenly start to grow, and when the temperature reaches a steady 15 to 20 degrees Celsius, they open. Lately, we don’t have cold winters, and the cherry blossoms have completely changed. First of all, the color has changed. It used to be darker.
This year, the temperature had already risen to 15 degrees Celsius by the end of February. So when the buds were still small, they were surprised and opened up. Then it got cold again in March. Thus, the buds remained open in an incomplete way.
So the blossoms cling to the branches in a half open situation, and cannot go on to the next stage. That situation has continued for two weeks. If the blossoms bloom and fall quickly as usual, the leaf-buds come out immediately. When those leaf-buds come out, another year for cheery trees starts. But this year, the leaf-buds are not coming out yet, which worries me a lot.
Somei Yoshino cherries suffer from climate change
There are three kind of cherry trees that grow naturally in Japan; Yama-zakura (prunus jamasakura), Higan-zakura (Prunus subhirtella), and Oshima-zakura (Prunus lannesiana var. speciosa). Their origin can be traced back to the Himalayas. It is said that there was once a Himalayan cherry, which was carried eastward little by little by birds and insects, reaching Japan after a long period of time. Japan’s climate with four seasons and bountiful water, resulted in favorable impact to cheery trees. Thus, cheery trees become common trees in Japan.
There are more than 300 kinds of cherry trees including gardening varieties. The Somei Yoshino cherry, which is the dominating cherry trees in Japan because of its popularity, is cultivated by human beings. The biggest reason why it has spread throughout the country is that they are easy to graft. And they grow quite rapidly. Furthermore, they blossom wherever they are planted.
The only difficulty is that since the Somei Yoshino cherry is produced by human beings, they have no seeds. They are also short lived and cannot bear offsprings. They do not have real trunks, as they are actually branches coming directly out of the soil. As a result, they cannot withstand harsh weather conditions such as rain and heat. They are destined to depend on human beings until their end.
Lately, there are more heavy rains in summer time. Somei Yoshino cherry trees are vulnerable to heavy rain because their roots get easily rotten. If the climate continues to change, Somei Yoshino cherry trees planted around the country will face a crisis.
It was just recently, more than 100 years after they are created, that it became apparent that Somei Yoshino cherry trees are short-lived. In the world of plants, the truth is often understood only after a century has passed. Plants cannot move. Since they just stand there, they think hard how to survive by trying to keep a balance. Because human beings are destroying the nature, the number of cherry trees is decreasing too. When a famous cherry tree faces its extinction, people try to protect that tree. But I think only trying to save the plants in front of us is meaningless. It’s not that there is something wrong with nature, but the problem lies with our way of livings. Isn’t it the life of human beings, with our unquestioning consumption and throwaway lifestyle, that must change?
Scientific reviewAs Mr. Sano explains, the Somei Yoshino is a man-made cherry tree. The Somei Yoshino breed that has spread throughout Japan is actually a clone, and this is the reason why all of them bloom at the same time. Temperature has a strong influence when these trees bloom. As the average temperature increases over the years, the blossom of cherry trees are becoming earlier and earlier. According to the Japan Meteorological Agency, the cherry blossom season across all of Japan has advanced an average of 4.2 days over the past 52 years. In big cities, the impact of the heat island phenomenon has accelerated this trend, resulting in an advance of 6.1 days over a 50 year period in average. In mid-sized cities, the advance is 2.8 days in average.1 (The study in question measured temperatures at 11 cherry blossom observation sites from among a total of six large cities and 17 medium cities in Japan.)
The blooming of cherry trees, however, depends not only on the warmth of the early spring, but also on winter temperature. Cherry trees enter a dormant state in autumn, and for them to come out of this state, there must be a prolonged period of low temperatures. Once they do come out of this state, another prolonged period of warmth is required before they actually start to bloom. In warm regions where the winter temperature has risen, this period of cold temperatures has become too short, and this impacted the cherry tree ecology. In some regions, the very survival of cherry tree is facing threat.2
According to the June,2008 report, “Kikohendo eno kashikoi tekio (Clever Adaptation to Climate Change)” issued by the Ministry of the Environment, by the period between 2082 and 2100, the average bloom date in the east and north of Japan is expected to advance a further 14.5 days over the average date as measured between 1981 and 2000. There is also the possibility of larger fluctuations in the cherry blossom period.3
Historically, the blooming of cherry trees has always been deeply intertwined with Japanese life, employed in virtually everything from agriculture to tourism. The shift in the cherry blossom season could alter the very way that Japanese people feel about the seasons.
- Japan Meteorological Agency, “Ijokisho report 2005 (Abnormal Weather Report 2005),” Chapter 2, Section 2.1.3: Seibutsu kisetsu gensho no henka (Changes in Biophenology). http://www.data.kishou.go.jp/climｃate/cpdinfo/climate_change/
- Keiko Masuda, “Kyushu chiho niokeru ondanka niyoru sakura no kaika to kaede no koyo eno eikyo (Influence of Warming Temperature in Kyushu region on Blooming of Cherry Trees and Color Changing of Autumn Maple Leaves),” Ryukoku Journal 26 (2): 65-76, 2005.
- Ministry of the Environment, “Kikohendo eno kashikoi tekio (Clever Adaptation to Climate Change),” Chapter 4, Section 4.3 (7): Shorai yosoku sareru eikyo “seibutsu kisetsu” (Predicted Future Impact on “Phenology”). http://www.env.go.jp/earth/ondanka/rc_eff-adp/index.html
All articles are subject to scientific review by a member of the Climate Witness Science Advisory Panel.