The flowers, which experience a “peak bloom” lasting only a few days, have been revered in Japan for over a thousand years. Crowds celebrate with spectator parties, flocking to popular photo spots and picnics under the branches.
But this year, cherry blossom season came and went in the blink of an eye, in one of the first blooms on record, and scientists warn that it is a symptom of the largest climate crisis threatening ecosystems. everywhere.
And in the capital Tokyo, cherry blossoms reached full bloom on March 22, the second-earliest date on record.
“As global temperatures warm, the last spring frosts are happening earlier and flowering happens earlier,” said Dr. Lewis Ziska of Environmental Health Sciences at Columbia Universities.
Peak bloom dates change each year, depending on numerous factors, including weather and rain, but they have shown a general tendency to move earlier and earlier. In Kyoto, the peak date stayed around mid-April for centuries, according to Aono’s data, but began to move in early April during the 19th century. The date has only dipped to the end of March a handful of times in recorded history.
“Sakura blossoms are very sensitive to temperature,” Aono said. “Flowering and full bloom can be earlier or later depending on the temperature alone,” he said. “The temperature was low in the 1820s, but it has risen about 3.5 degrees Celsius (6.3 degrees Fahrenheit) to this day.”
This year’s seasons in particular influenced flowering dates, he added. Winter was very cold, but spring came quickly and unusually warm, so “the buds are fully awake after enough rest.”
However, its early flowering 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 that makes flowers bloom earlier: urbanization and climate change. With increasing urbanization, cities tend to heat up more than the surrounding rural area, in what is called the heat island effect. But a more important reason is climate change, which has caused a rise in temperatures in the region and the world.
And these early dates are not just a matter of tourists struggling to reach full bloom before all the petals fall; they could have a lasting impact on entire ecosystems and threaten the survival of many species.
For every action there is a reaction
Plants and insects are highly dependent on each other, and both use environmental cues to “regulate the timing of different stages of their life cycles,” Tai said. For example, plants sense the temperature around them, and if it is warm enough for a constant period, they begin to bloom and their leaves begin to emerge. Similarly, insects and other animals are temperature dependent 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, from thousands to millions of years,” said Tai. “But in the last century, climate change is really ruining everything and disrupting all these relationships.”
Different plants and insects can respond to increased heat at different rates, throwing their life cycles out of balance. Whereas they once timed their growth simultaneously each spring, now flowers can bloom before insects are ready, and vice versa, which means that “insects may not find enough food to eat from plants, and plants do not have enough pollinators (to reproduce), “he said.
“Ecosystems are not used to these kinds of big fluctuations, it causes them a lot of stress,” said Tai. “Productivity can be reduced and ecosystems can even collapse in the future.”
It is not limited to cherry blossoms.
And the effects of climate change are not just limited to cherry blossoms. “Cherry blossoms are eye-catching, people love to go see them, but many other plants are also undergoing life cycle changes and may have an even greater influence on the stability of their ecosystems, “said Tai.
In some regions, farmers may be forced to change the types of crops they grow. Some climates will become too hot for what they are growing now, while other climates will see more flooding, more snow, more moisture in the air, which will also limit what can be grown.
“(Farmers) have a harder time predicting when they will have a good year, when they will have a bad year,” Tai added. “Farming is more like a gamble now, because climate change is randomizing things that happen in our ecological systems.”