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 flower display parties, gathering in 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, in one of the most anticipated blossoms ever recorded in history. Scientists warn that the fact is a symptom of a major climate crisis, which threatens ecosystems everywhere.
Yasuyuki Aono, a researcher at Osaka Prefecture University, has collected records from Kyoto since AD 812, from historical and daily documents. In Kyoto City, cherry blossoms peaked in 2021 on March 26, the first in more than 1,200 years, Aono said. 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 coming sooner,” said Dr. Lewis Ziska, from the Department of Environmental Health Sciences at Columbia University in the United States.
Peak flowering dates change each year, depending on several factors, including climate and rainfall, but have shown a general tendency to move forward more and more. In Kyoto, the peak date hovered around mid-April for centuries, according to Aono’s data, but it started to move into early April during the 19th century. The date fell to the end of March just one handful of times in recorded history.
“Cherry blossoms are very sensitive to temperature,” said Aono. “Flowering and full flowering can occur sooner or later, depending only on the temperature. The temperature was low in the 1820s, but it has risen by about 3.5 degrees Celsius to this day ”.
According to him, the seasons of this year, in particular, influenced the flowering dates. The winter was very cold, but the spring came quickly and exceptionally hot, so “the buds are fully awake after enough rest”.
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.
The anticipation of the bloom does not only affect tourists struggling to travel at the peak of the season before all the petals fall: it can have a lasting impact on entire ecosystems and threaten the survival of many species.
Action and reaction
Plants and insects depend a lot on each other, and both use environmental cues to “regulate the time of different stages of their life cycles,” said Tai. For example, plants sense the temperature around them. If it is warm enough for a consistent period, they begin to bloom and their leaves begin 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 thousands to millions of years. But in the most recent century, climate change is really destroying everything and disrupting all of those interactions. ”
Different plants and insects can respond to increased heat at different rates, taking the synchrony out of their life cycles. Whereas before they clocked their growth simultaneously each spring, now flowers can bloom before the insects are ready, and vice versa, which means that “insects may not find enough food to eat on the plants, and the plants cannot they have enough pollinators (to reproduce), ”said Professor Tai.
In the past decade, some plant and animal populations have already begun to move to “higher altitudes” and “higher latitudes” to escape the effects of climate change, according to a 2009 study published in “Biological Conservation”. But it is becoming more difficult for ecosystems to adapt, with climate change making the climate increasingly unpredictable. Although the trend in flowering dates is generally moving earlier, the unexpected and extreme weather means that there is still a great deal of variability year on year.
“Ecosystems are not used to this type of large fluctuation, this causes a lot of stress. Productivity can be reduced and ecosystems may even collapse in the future, ”said Tai.
Not only the cherry trees
The change in flowering dates this year is not just limited to Japan: the cherry blossoms that adorn the Tidal Basin in the US capital, Washington, also opened earlier. According to the National Park Service, Washington’s peak cherry blossom date has advanced nearly a week from April 5 to March 31.
In addition, the effects of climate change are not limited to cherry blossoms. “Cherry blossoms attract attention, 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 the professor. Tai.
The same phenomenon is already happening with many economically valuable crops and plants – posing major problems for food security and farmers’ livelihoods. Food supplies in some of the world’s most vulnerable regions are being directly affected by droughts, crop failures and swarms of locusts.
In some regions, farmers may be forced to change the types of plantations they cultivate. Some climates will be too hot for what is being planted now, while other climates will see more flooding, more snow, more moisture in the air, which will also limit what can be cultivated.
“Farmers have a much harder time predicting when they will have a good year and when they will have a bad year,” added Professor Tai, from Hong Kong. “Agriculture is now more of a gamble, because climate change is making random what happens in our ecological systems ”.
(Translated text. Click here to read the original in English).
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