Posted by Richard
Primack
The flowering of
cherry trees is one of the most beautiful sights in the spring. Cherry trees
are also extremely sensitive to temperature, flowering earlier in warm years
and later in cold years. The Japanese people greatly enjoy their annual cherry
blossom festival, taking time off from work, walking under the trees, and
meeting friends for outdoor parties. In
Tokyo, a warming climate has caused the blooming of the cherry trees to
gradually change over the last century from mid-April to late March.
Figure 1.
The oldest records
of cherry blossom flowering come from Kyoto where the festival has been
celebrated for over 1200 years. There have been long periods of earlier
flowering and later flowering associated with global changes in temperature. Starting
about 150 years ago, the cherry trees have been flowering ever earlier due to a
combination of urbanization in Kyoto (more buildings, more pavement and
streets, and fewer trees) and warming temperatures. Over recent decades, cherry
trees in Kyoto have been flowering earlier than they ever have in the past.
Figure 2. Cherry blossoms in Japan are getting earlier over time, and have been particularly early in recent years
The effect of
urbanization on cherry trees is illustrated by the city of Osaka. Using 80
observation points around the city, researchers show that trees flower earliest
in the center of the city where it is warmest due to urbanization.
Figure 3. This map
of Osaka shows that trees flower earliest in the center of the city
To read more about
cherry blossoms as indicators of climate change, see our articles in Biological Conservation and Arnoldia.
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