Because of climate change, plants in the United Kingdom are flowering an average of 26 days earlier than they did before 1987, a new study in the Proceedings of the Royal Society B finds.
Researchers examined over 400,000 records from Nature’s Calendar, a citizen science database with observations dating back to 1736. They looked at first flowering dates for 406 flowering plant species and compared those to temperature measurements. The researchers found the average first flowering date before 1987 was May 12, but from 1987 to 2019, that average shifted to April 16—almost a month earlier, per the study.
“The results are truly alarming because of the ecological risks associated with earlier flowering times,” says lead study author Ulf Büntgen, a climate scientist at the University of Cambridge, in a statement. A late frost can kill early flowers, but Büntgen says an even bigger risk is ecological mismatch, which occurs when a relationship between wildlife is interrupted by changes in the timing of life-cycle events like breeding or migrating.
“A certain plant flowers, it attracts a particular type of insect, which attracts a particular type of bird, and so on,” Büntgen says in the statement. “But if one component responds faster than the others, there’s a risk that they’ll be out of sync, which can lead species to collapse if they can’t adapt quickly enough.”
Researchers used observations of flowering dates for four plant categories based on height: trees, shrubs, herbs and climbers. Herbs saw the most pronounced shift in their first flowering date, at 32 days. This change may be because short-lived plants that have faster turnover rates can adaptively evolve quicker, the study states. Whether they can do this quickly enough to keep pace with climate change is unknown.
The study also looked at plant location and found that southern sites flowered six days earlier than northern sites; urban areas flowered five days earlier than rural ones; and lower elevations flowered one day earlier than higher elevations.
John David, head of horticultural taxonomy for the Royal Horticultural Society (RHS), tells BBC News’ Helen Briggs that he’s noticed early blooming in RHS gardens.
"The main focus of this study is on native plants and so we don't yet have a clear picture of the full impact of these changes on garden plants, but would expect a similar pattern and have seen indications of this in our own RHS gardens such as the apple flowering times in our orchard at RHS Garden Wisley," he says to BBC News.
The study concludes that “if plants in the U.K. continue to flower earlier, and if the frequency, intensity and duration of climatic extremes increase further, the functioning and productivity of biological, ecological and agricultural systems will be at an unprecedented risk.”
Last year, Japan saw similar trends in its cherry blossoms. Kyoto recorded the earliest bloom since the Japan Meteorological Agency started keeping data in 1953, writes Mari Yamaguchi for the Associated Press.