Why is cherry blossoming a concern in Japan?
2:03
(CNN) -
If you think of Japan in spring, the image that comes to mind is probably one of the country's famous cherry blossoms.
They are also known as
"sakura"
: white and pink flowers, which sprout in cities and mountains, covering the ground with their petals.
But the fact that they sprout earlier and earlier is a warning about climate change.
The flowers, which experience a "peak bloom" lasting only a few days, have been revered in Japan for more than 1,000 years.
Crowds celebrate with observation gatherings, going to the most popular spots to take photos and have picnics under the branches.
But this year, Japan's cherry blossom season has come and gone in the blink of an eye, in one of the earliest blooms on record, and scientists are warning it's a symptom of the great climate crisis that threatens ecosystems around the world.
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Yasuyuki Aono, a researcher at Osaka Prefectural University, has compiled Kyoto records dating back to AD 812 from historical and daily documents.
In Japan's central city of Kyoto, cherry blossoms peaked on March 26, the earliest in more than 1,200 years, according to Aono.
And in the capital Tokyo, cherry blossoms reached their peak on March 22, the second-earliest date on record.
"As global temperatures warm, the last spring frosts come earlier and flowering comes early," says Dr. Lewis Ziska, from Columbia University Environmental Health Sciences.
A bird stands next to cherry blossoms in a park in Tokyo, Japan, on March 23.
This is how cherry blossom dates have changed in Japan
The dates of maximum flowering change each year, depending on numerous factors such as weather and rainfall, but they show a general tendency to get ahead more and more.
According to Aono's data, in Kyoto, the date of maximum flowering has oscillated for centuries around mid-April, but began to move in early April during the 19th century.
The date has only fallen at the end of March on a handful of times in history.
"Cherry blossoms are very sensitive to temperature," explains Aono.
"Flowering and full bloom can be advanced or delayed only depending on the temperature," he said.
"The temperature was low in the 1820s, but it has risen about 3.5 degrees Celsius so far."
This year's seasons, in particular, influenced flowering dates, he added.
Winter was very cold, but spring came quickly and unusually warm, so "the shoots are fully awake after getting 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, associate professor of earth sciences at the Chinese University of Hong Kong.
Early flowering factors
Increased heat, which is the main factor that causes flowers to bloom earlier, has two sources: urbanization and climate change.
With increasing urbanization, cities tend to get hotter than surrounding rural areas.
This is called the heat island effect.
But a bigger reason is climate change, which has caused temperatures to rise throughout the region and around the world.
And these earlier dates aren't just a matter of tourists rushing to see the peak of bloom before all the petals fall off - it could have a lasting impact on entire ecosystems and threaten the survival of many species.
Cherry blossoms at Kitanomaru Park in Tokyo, Japan, on March 23.
For every action there is a reaction
Plants and insects depend on each other.
Both use signals from the environment to "regulate the timing of different stages of their life cycles," explains Tai.
For example, plants sense the temperature around them and, if it remains warm enough for a constant period of time, they begin to flower and sprout leaves.
Insects and other animals also depend on temperature for their life cycles, so increased heat can cause faster growth.
"The relationship between plants and insects and other organisms has developed over many years, between thousands and millions of years," explains Tai.
"But in the last century, climate change is messing everything up and disrupting all these relationships."
Different plants and insects may respond to increased heat at different rates, desynchronizing their life cycles.
Whereas before they grew simultaneously every spring, now the flowers can bloom before the insects are ready, and vice versa.
This means that "insects may not find enough food in plants, and plants do not have enough pollinators (to reproduce)," he said.
Trees would lose their leaves sooner due to climate change 1:03
In the last decade, some populations of plants and animals began to move to "higher altitudes" and "higher latitudes" to escape the effects of climate change, according to a 2009 study in Biological Conservation.
But ecosystems are finding it increasingly difficult to adapt.
This is because climate change makes the weather increasingly unpredictable.
Although the trend of flowering dates is generally ahead, the unexpected and extreme weather means that there is still a huge variability from one year to the next.
"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."
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It is not limited to cherry blossoms
This year's blooming date change isn't just limited to Japan;
the cherry blossoms that adorn the Washington City Tidal Basin also bloomed early.
According to the National Park Service, the peak bloom date for Washington cherry trees has been moved forward nearly a week, from April 5 to March 31.
Fly over the cherry blossoms in Washington 0:45
And the effects of climate change are not limited to these flowers.
"Cherry blossoms attract attention, people love to go see them, but many other plants are also undergoing changes in their life cycle, and they may have an even greater influence on the stability of their ecosystems," said Tai.
The same phenomenon is already happening with many economically valuable crops and plants, he said, posing big problems for food security and farmers' livelihoods.
The food supply in some of the world's most vulnerable regions is directly affected by droughts, poor harvests and locust clouds.
In some regions, farmers may be forced to change their crops.
Some climates will become too hot for what is grown now.
While other climates will see more flooding, more snow, more humidity 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 and when a bad year," added Tai.
"Farming is now more of a gamble, because climate change is making things that happen in our ecological systems more random."
agriculture climate change spring drought