Scientists at the Smithsonians National Museum
|NMNH Botanist Stanwyn Shetler and colleagues Mones Abu-Asab, Paul Peterson, and Sylvia Stone Orli have analyzed 30 years of observations about the first dates of blossoming for 100 species of plants common to the Washington, DC area. They have found that the rise in the region's average minimum temperatures is producing earlier flowering in 89 of the 100 species observed. On average, the plants are blossoming 4.5 days earlier in 2000 than in 1970 - and for Washington's famous cherry trees, this means that the cherry blossoms are now arriving a week earlier than 30 years ago.|
The scientists examined botanical data collected at the Smithsonian's Department of Botany by more than 125 individuals over a 30-year period beginning in 1970 in order to reach their findings. Data were obtained at sites in Washington, D.C.; Arlington, Virginia; Beltsville and Silver Spring, Maryland; and other regional locations.
Using data from the National Park Service, Shetler,
Abu-Asab, Peterson and Orli also examined two predominant species of Japanese
flowering cherries located near the Tidal Basin in Washington, DC, which have
been blooming on earlier dates over the past 30 years. The Oriental cherry blossom
(Prunus serrulata) and the Yoshino cherry blossom (Prunus x yedoensis) have been
reaching peak bloom six and seven days earlier since the 1970s, respectively. This year, the Yoshino variety reached
peak bloom on March 20, the second earliest date on record.
The consequences of the environmental changes indicated by the earlier flowering could be significant, as Shetler explained, "Based on this study, we can expect a gradually expanding growing season, which may be lengthened at both ends if warmer temperatures prolong the end of summers as well. Over a long period the species composition of our local flora could change. Species like the sugar maple that require a long cold period may die out in our region. Invasive alien species, especially from more southern climes, may become more and more of a problem. Weedy species like false-strawberry that can bloom through relatively mild winters could spread. If these trends continue, persons with allergy problems will experience them earlier because some of the first plants to bloom are wind-pollinated trees, such as the American elm and common alder."
NMNH botanists will continue to study the flowering patterns of local plant species in order to contribute to the general understanding of the effects of global warming.
Shetler and Orli are also the authors of the new Annotated Checklist of the Vascular Plants of the Washington-Baltimore Area (Part I - Ferns, Fern Allies, Gymnosperms, and Dicotyledons). Its publication represents the initial step toward providing the first inventory of the vascular flora in the Washington, D.C. area in more than 50 years.
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2000 - NMNH