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Cherry Blossoms in DC: A Casualty of Climate Change?
National Cherry Blossom Festival 2016
The 2016 National Cherry Blossom Festival will take place March 20-April 17, with the festival parade occurring on April 16 from 10:00 AM to Noon along Constitution Avenue.
The annual National Cherry Blossom Festival in Washington DC is both a local rite of spring and a source of national pride. More than 1.5 million tourists from across the country and around the world flock to the nation's capital in late March and early April every year to witness the blooming of Washington's famous cherry trees, generating an estimated $126 million every year in tourist revenue for the local economy.
The festival is timed to coincide with the peak blooming period of Washington's 3,750 cherry trees. On average over the past century, this peak bloom date has fallen around April 4. In recent decades, however, an earlier onset of warmer temperatures has been nudging the trees' peak blooming period earlier in the year to the last week in March.
Tourists visiting DC toward the end of the National Cherry Blossom Festival in recent years have been missing the peak bloom, finding wilting flowers and fallen petals around the Tidal Basin rather than picturesque explosions of pink and white. This makes Washington DC's cherry trees an important and very visible indicator of climate change.
The National Mall and Tidal Basin
The History of Washington's Cherry Blossoms
The idea of planting Japanese cherry trees in the Nation's Capital was first proposed by Eliza Ruhamah Scidmore, a writer, photographer, and sister of a career diplomat who served multiple assignments in Japan. Beginning in 1885, Scidmore repeatedly wrote to successive U.S. Army Superintendents of the Office of Public Buildings and Grounds requesting that cherry trees be planted along the Potomac waterfront. Her requests were ignored.
In 1909, Scidmore found a more receptive audience in the incoming First Lady of the United States, Helen Taft. Taft agreed with Scidmore's suggestion and asked the Office of Public Buildings and Grounds to begin planting cherry trees along the District's southwest waterfront.
When Japanese diplomats learned of the plans to plant cherry trees in the nation's capital, the Embassy arranged for an additional 2,000 cherry trees to be given to the city of Washington from the city of Tokyo as a goodwill gift. In January of 2010, the trees arrived in Washington. Unfortunately, inspection teams from the Department of Agriculture found that the trees were infested with insects and roundworms, and the entire gift of 2,000 trees had to be burned to protect American farmers from infestation.
Though this embarrassing situation could have turned into a diplomatic disaster, a cordial exchange of apologies between the Department of State and the Japanese Embassy saved the day. The Mayor of Tokyo arranged for a second gift of more than 3,000 trees to be given to the city of Washington - this time carefully selected and grafted to avoid infestation.
In 1912, the new cherry trees arrived in Washington and the first two were ceremonially planted on the northern bank of the Tidal Basin by First Lady Helen Taft and Viscountess Chinda, wife of the Japanese Ambassador. These first two trees are still growing today, and can be found near the end of 17th Street, SW, where they join the more than 3,700 cherry trees around the Tidal Basin and along the National Mall.
Timing The Cherry Tree Bloom
Though the original 1912 gift from Japan contained about a dozen varieties of cherry tree, there are two main cultivars that dominate Washington's National Mall.
The vast majority of trees around the Tidal Basin are of the Yoshino variety (Prunus × yedoensis), a hybrid of two Japanese cherry tree species that was first cultivated in Tokyo in the early 18th Century. Yoshino cherry trees boast fragrant white flowers during the peak blooming period and produce a cherry fruit, though one that is not very palatable for human tastes. Kwanzan cherry trees (Prunus serrulata) are the other dominant species around the National Mall, producing bright white and pink flowers about two weeks after the Yoshino trees.
Peak blooming date is defined by the National Park Service as the date on which 70% of the blossoms are open on the Yoshino trees around the Tidal Basin. Predicting the peak blooming date is nearly impossible more than 10 days out, as this date depends heavily on weather conditions as the buds are developing.
Horticulturalists from the National Park Service monitor five stages of bud development prior to peak bloom:
- Buds on cherry trees begin turning green in late February to early March. Each bud will become a cluster of flowers.
- The buds split into florets - the individual developing flowers in the cluster - in mid March, 2-3 weeks before peak bloom.
- Florets begin to extend and form points in mid to late March, 12-17 days before peak bloom.
- The peduncle, or stem supporting each cluster of flowers, elongates in late March, 6-10 days before peak bloom.
- Finally, the florets turn from green and pink to puffy white 4-6 days before blooming.
The timing of these stages can vary widely from year to year depending on weather conditions. In February 2010, for example, Washington was hit by a series of blizzards nicknamed "Snowmageddon" in the local press. That year, buds did not turn green until March 15, but reached peak bloom a mere two weeks later on March 31. The winter of 2008, on the other hand, was mild in the DC area, with temperatures about three degrees above average. Cherry blossom buds began turning green in mid-February, but the trees reached peak bloom six weeks later on March 26.
Climate Change and Cherry Blossoms
Although the actual peak bloom dates vary from year to year, a definite trend can be seen when looking at the data from last few decades. From 1960-1969, peak bloom date occurred on or after April 4 - the historical average - seven times. In the 1970s, there were five peak blooms on or after the average date - half of the time. In both the 1980s and 1990s, peak bloom date occurred after April 4th only four times. Since 2000, only two peak blooms have occurred after the historical average.
This trend certainly suggests that the changing climate is having an impact on Washington's famous cherry blossoms. How much of an impact was the subject of a paper published in 2011 by a group of scientists led by Uran Chung, now Research Fellow at APEC Climate Center in Busan, South Korea.
Chung and her colleagues constructed a model for predicting cherry blossom blooming times based on daily temperature highs and lows. Blooming time for flowering plants depends on the number of "chilling days" trees spend during their dormant period in the fall and winter, and the number of "heating days" they spend warming up as spring approaches. Harsh winters will have more chilling days, delaying blooming times. Mild winters will have more heating days, resulting in earlier blooms.
Checking their model against historical temperature data collected at Reagan National Airport, just across the Potomac in Arlington, Virginia, Chung and her colleagues found that the model was remarkably successful - predicting the peak bloom date to within 3 1/2 days for the years between 1951 and 2010.
Applying this model to future scenarios of a changing climate, the researchers found that in the best-case scenario, cherry blossoms will reach their peak in the last week of March in the 2040s to 2060s, and in mid-March from 2070 to the end of the century. This scenario assumes that population growth will peak and decline at mid-century and technology will work to mitigate the effects of climate change.
In the worst-case scenario - in which world population continues to grow and little, if any, measures are taken to slow or reverse the production of greenhouse gases - the peak bloom date will move much more rapidly. By mid-century, Washington's cherry blossoms will be blooming in the middle of March. Toward the end of the century, peak bloom dates will average around March 5, and in many years will occur in late February.
The Changing Climate
Climate change is a very abstract concept to grasp, with climatologists talking in terms of albedo and radiative forcing and changes to global average temperatures. These broad, general descriptions of climate change can overlook what climate change actually entails - thousands of individual effects on plant and animal species in a multitude of local ecosystems everywhere in the world.
The cherry trees around Washington DC's Tidal Basin are just a handful of these species. In addition to being an important cultural symbol and a driver of the region's tourism economy, the cherry trees are a visible example of how climate change is affecting all of us, and a predictor of how it will continue to impact our world in the future.
Sources and Further Information
- Bloom Watch | National Cherry Blossom Festival
Exactly when the buds will open is not easy to predict and it is extremely difficult to give an accurate forecast much more than 10 days before peak bloom.
- Cherry Blossom Festival $126M Bonanza for DC
The National Cherry Blossom Festival is a cherished rite of spring, coloring the capital with delicate pink and white blossoms—and attracting tourists from far and wide.
- HISTORY OF THE CHERRY TREES - National Park Service
The plantings of cherry trees originated in 1912 as a gift of friendship to the People of the United States from the People of Japan.
- Climate Change and Cherry Tree Blossom Festivals in Japan (pdf)
The dates of cherry tree festivals in Japan have emerged as one of the most important sources of information on the impacts of climate change on plants.
- PLOS ONE: Predicting the Timing of Cherry Blossoms ... in Response to Climate Change
Cherry blossoms, an icon of spring, are celebrated in many cultures of the temperate region. For its sensitivity to winter and early spring temperatures, the timing of cherry blossoms is an ideal indicator of the impacts of climate change...