Flowers, which experience a “flowering peak” that lasts only a few days, have been revered in Japan for over a thousand years. Crowds celebrate with exhibition parties, going to the most popular places to take pictures and have picnics under the branches.
But this year, the cherry blossom season has come and gone in the blink of an eye, on one of the first flowers ever recorded – and scientists warn that it is a symptom of a major climate crisis that threatens ecosystems everywhere.
And in the capital Tokyo, cherry blossoms blossomed on March 22, the second oldest date on record.
“As global temperatures rise, last spring’s frosts are occurring earlier and flowering is occurring earlier,” said Dr. Lewis Ziska of Columbia University Environmental Health Sciences.
Peak flowering dates change each year, depending on several factors, including climate and rainfall, but have shown a general tendency to move earlier and earlier. In Kyoto, the peak date hovered around mid-April for centuries, according to Aono’s data, but started to move in early April during the 19th century. The date fell to the end of March just a handful of times in recorded history.
“Sakura’s flowers are very sensitive to temperature,” said Aono. “Flowering and full flowering can occur sooner or later, depending only on the temperature,” he said. “The temperature was low in the 1820s, but it has risen by about 3.5 degrees Celsius (6.3 degrees Fahrenheit) to this day.”
This year’s seasons, in particular, influenced the flowering dates, he added. The winter was very cold, but the spring came quickly and exceptionally hot, so “the buds are fully awake after enough rest”.
Its early flowering, however, is just the tip of the iceberg of a global phenomenon that could destabilize countries’ natural systems and economies, said Amos Tai, assistant professor of earth sciences at Hong Kong’s Chinese University.
There are two sources of increased heat, which is the main factor that causes flowers to bloom earlier: urbanization and climate change. As urbanization increases, cities tend to get warmer than the surrounding rural area, in what is called the heat island effect. But a bigger reason is climate change, which has caused temperatures to rise in the region and worldwide.
And those earlier dates are not just a matter of tourists struggling to catch the flower peak before all the petals fall – they can have a lasting impact on entire ecosystems and threaten the survival of many species.
For all the action there is a reaction
Plants and insects are very dependent on each other, and both use environmental cues to “regulate the time of different stages of their life cycles,” said Tai. For example, plants feel the temperature around them and if it is warm enough to a consistent period, they start to bloom and their leaves start to emerge. Likewise, insects and other animals depend on temperature for their life cycles, which means that higher heat can cause faster growth.
“The relationship between plants and insects and other organisms has developed over many years – thousands to millions of years,” said Tai. “But in the recent century, climate change is really destroying everything and disrupting all of those relationships.”
Different plants and insects can respond to increased heat at different rates, throwing their life cycles out of sync. Whereas before they clocked their growth simultaneously each spring, now flowers can bloom before the insects are ready, and vice versa – meaning that “insects may not find enough food to eat on the plants, and the plants don’t have enough pollinators (to reproduce), “he said.
“Ecosystems are not used to these types of large fluctuations, it causes them a lot of stress,” said Tai. “Productivity may be reduced and ecosystems may even collapse in the future.”
Not limited to cherry blossoms
And the effects of climate change are not limited to cherry blossoms. “Cherry blossoms are noteworthy, people love to go and see them, but many other plants are also undergoing changes in their life cycle and can have an even stronger influence on the stability of their ecosystems,” said Tai.
In some regions, farmers may be forced to change the types of plantations they cultivate. Some climates will be too hot for what is growing now, while other climates will see more floods, more snow, more moisture in the air, which will also limit what can be grown.
“(Farmers) have a much harder time predicting when they will have a good year, when they will have a bad year,” added Tai. “Agriculture is now more of a gamble, because climate change is randomizing the things that happen in our systems ecological. “