The flowers, which experience a “peak bloom” that lasts only a few days, have been revered in Japan for over a thousand years. Crowds celebrate with viewing parties, flocking to the most popular locations to take photos and picnic under the branches.
But this year, cherry blossom season has come and gone in the blink of an eye, in one of the earliest blooms ever – and scientists warn it’s a symptom of the greater climate crisis threatening ecosystems everywhere.
And in the capital Tokyo, cherry blossoms reached their full bloom on March 22, the second earliest date on record.
“As the temperature on Earth gets warmer, the last spring frosts fall earlier and bloom starts earlier,” says Dr. Lewis Ziska from Columbia Universities Environmental Health Sciences.
Peak bloom dates shift each year depending on numerous factors including weather and rainfall, but have shown a general trend to move earlier and earlier. In Kyoto, the peak date hovered around mid-April for centuries, according to Aono data, but started shifting in early April in the 19th century. The date has only dived a few times in recorded history in late March.
“Sakura flowers are very sensitive to temperature,” says Aono. “Bloom and full bloom can be earlier or later, depending on the temperature alone,” he said. “The temperature was low in the 1820s, but has risen by about 3.5 degrees Celsius to this day.”
This year’s seasons in particular influenced blossom dates, he added. Winter was very cold, but spring came quickly and unusually warm, so “the buds are fully awake after a good rest.”
However, their early bloom is just the tip of the iceberg of a global phenomenon that could destabilize natural systems and countries’ economies, said Amos Tai, assistant professor of earth sciences at the Chinese University of Hong Kong.
There are two sources of increased heat, which is the main factor causing the flowers to bloom earlier: urbanization and climate change. With increasing urbanization, 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 led to rising temperatures across the region and the world.
And these earlier dates aren’t just a matter of tourists scrambling to catch the peak blooms before the petals all fall – they can have a lasting impact on entire ecosystems and threaten the survival of many species.
There is a reaction for every action
Plants and insects are highly dependent on each other, and both use environmental factors to “regulate the timing of different stages of their life cycle,” Tai said. For example, plants sense the temperature around them and when it is warm enough for a constant period of time, they begin to bloom and their leaves begin to appear. Likewise, insects and other animals depend on temperature throughout their life cycle, which means that higher heat can cause faster growth.
“The relationship between plants and insects and other organisms has evolved over many years – thousands to millions of years,” said Tai. “But in the past century, climate change has really destroyed everything and disrupted all these relationships.”
Different plants and insects can respond to the rise in heat at different rates, causing their life cycles to be out of sync. While they once timed their growth simultaneously every spring, now flowers can bloom before the insects are ready, and vice versa – meaning that ‘the insects may not find enough food to eat from the plants, and the plants do not have enough pollinators (to reproduce), ”he said.
“Ecosystems are not used to these kinds of big fluctuations, it causes a lot of stress,” said Tai. “Productivity may decline and ecosystems may even collapse in the future.”
Not limited to cherry blossoms
And the effects of climate change aren’t just limited to cherry blossoms. “Cherry blossoms are eye-catching, people like to go to them, but many other plants are also experiencing changes in their life cycles and may have an even greater impact on the stability of their ecosystems,” Tai said.
In some regions, farmers may be forced to change the types of crops they grow. Some climates will get too hot for what they are growing now, while other climates will see more flooding, more snow, and 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. “Farming is more of a gamble now, as climate change randomly distributes things that happen in our ecological systems.”