Earlier Springs Raise Risks of Freeze Damage to Crops, Blossoms
Global warming drives seasonal changes. In the United States, studies have documented an advance in the timing of springtime lifecycle events across plant and animal species in response to increased temperatures.
According to the 2014 US National Climate Assessment, “Observed long-term trends towards shorter, milder winters and earlier spring thaws are altering the timing of critical spring events such as bud burst and emergence from overwintering.”
However, warmer winters have the potential to create major disrupts in fruit production and other agriculture and ecosystem productions if the historical sequence of thaw and freeze is also disrupted. Freeze following unusually early thaw can cause major damage to crops such as when early blooms are killed by freeze following thaw so that fruits fail to set.
Columbia, S.C. had two consecutive nights in the 20s last week. While that’s normally not a problem, as the average date of the last freeze there is March 30, this freeze caused major damage to crops there and across the Southeast, coming as it did after an exceptionally warm February that encouraged plants to bloom much earlier than normal.
As the climate warms further, plants will tend to bud and blossom earlier, increasing the risk of damage from an early season frost or freeze. This will lead to more year-to-year variability on the arrival of blooms and leaves, and thus the risk to agriculture will be on the rise.
Last week’s freeze did tremendous damage to the peach and blueberry crops in the Palmetto State. According to the South Carolina Department of Agriculture, farmers are hoping to eke out just 10 to 15 percent of their usual peach crop. Blueberry losses are similar in scope.
Farther north, the famed cherry blossoms in Washington, D.C., are holding on, but they are still nowhere near as vibrant as they normally are. According the Washington Post, more than half of the fully developed blossoms were destroyed by the most recent freeze, as there were seven consecutive nights below freezing in the 10 days leading up to the first day of spring on Monday.
Like the trees and bushes in South Carolina, the cherry blossoms along the Tidal Basin were far ahead of schedule in 2017. The first green buds appeared on Feb. 24, the earliest since 2008. Peak bloom will probably come during the upcoming weekend (March 25-26), which is also earlier than normal, but there is probably another freeze to get past on Wednesday night before a prolonged warmer period follows into the weekend.
While there is tremendous variation in the temperature from one year to the next on the first day of spring, as this interactive from the National Oceanic and Atmospheric Administration indicates, there is a general trend toward warmer winters, and thus earlier starts to spring.
Nationwide, spring already arrives about three days earlier than it did 30 years ago, and it may begin nearly two weeks earlier on average 30 years from now.
As the planet continues to warm from the increasing greenhouse gases building in the atmosphere, the winters will continue to warm correspondingly, leading to the earlier budding and flowering of trees. Today, D.C.’s cherry blossoms, on average, peak about five days earlier than they did 80 years ago.
The earlier blooms also suggest a slower progression of spring. After a cold winter with snow, soils warm quickly leading to rapid blooming. But warmer winters, particularly with less snow, result in plants drawing out the progression from winter hibernation to full spring bloom, a University of New Hampshire study released this month showed.
That lengthening process means plants may bloom out of sync with migrating pollinators, adding further stress to both wild plants and crops alike.