If you’ve noticed that spring blossoms are arriving earlier than in years past and wondered whether it has anything to do with a warming climate, the simple answer is yes. And it’s happening much sooner than current models predict.
As it happens, the field of phenology — the study of periodic biological phenomena, including flowering, breeding, and migration relative to climatic conditions — provides one of the most reliable barometers of climate change, and a new, large-scale review of historical records confirms that many species are now flowering and leafing out earlier as temperatures rise.
Cherry blossoms in Washington, D.C., have been blooming earlier in recent decades, including a very early March bloom this year. Credit: Elizabeth Wolkovich, Biodiversity Research Centre, University of British Columbia-Vancouver
Included in the study, published online last week in the journal Nature, were historical data from 1,558 species of wild plants on four continents dating back decades and in some cases, centuries. The records showed that leafing and flowering will advance, on average, five to six days per degree Celsius — a finding that was consistent across species and datasets.
Predicting how plants will respond to climate change is critical not only to agriculture but to the health of natural ecosystems as well. Typically, ecologists will conduct controlled experiments by creating warmer conditions in small plots to learn how different species will react. Observed plant responses are then incorporated into models to predict future ecosystem changes as temperatures around the globe continue to rise.
The new study of historically observed data, however, shows the warming experiments to be dramatically underestimating how plants respond to climate change, and suggests a reevaluation is needed as to how they are conducted.
Researchers with the Boston-Area Climate Experiment are using techniques in their plant-warming experiments designed to better reflect natural daily and seasonal temperature cycles. This experiment is too new to have been in included in the Nature study, but its design addresses some of the concerns raised. Credit: Jeff Dukes, Purdue University
“This suggests that predicted ecosystem changes — including continuing advances in the start of spring across much of the globe — may be far greater than current estimates based on data from warming experiments,” said Elizabeth Wolkovich, who led the interdisciplinary team of scientists behind the new research while she was a postdoctoral fellow at the University of California, San Diego.
“The long-term records show that phenology is changing much faster than estimated based on the results of the warming experiments. This suggests we need to reassess how we design and use results from these experiments.”
