Climate change

Springing a surprise

Print edition : March 30, 2018

Cherry trees have begun to bloom earlier than usual in Taiwan. Scientists have warned that this may be the result of global warming. Photo: AFP

Spring, the season of new beginnings and fresh buds, has been arriving earlier than usual, thanks to changes associated with global warming. While most of us have already noticed this phenomenon, the key question is how much earlier. A team of researchers led by the ecologist Eric Post at the University of California, Davis, in the United States may have cracked the code.

According to their study, published recently in the journal Scientific Reports, for every 10° north from the equator, spring arrives about four days earlier than it did a decade ago. This northward increase in the rate of springtime advance is roughly three times greater than what previous studies have indicated. In the Arctic, it could arrive as many as 16 days earlier.

“This study verifies observations that have been circulating in the scientific community and popular reports for years,” said Post, a Fellow of the John Muir Institute and polar ecologist in the Department of Wildlife, Fish and Conservation Biology, U.C. Davis. “Yes, spring is arriving earlier, and the Arctic is experiencing greater advances of spring than lower latitudes. What our study adds is that we connect such differences to more rapid springtime warming at higher latitudes.”

The study is the most comprehensive analysis to date of springtime advance, or phenology, as you move north with latitude. Such signs include birds migrating, flowers blooming, amphibians calling and leaves emerging.

The scientists arrived at this conclusion by analysing 743 previously published estimates of the rate of springtime advance from studies spanning 86 years across the northern hemisphere, as well as rates of springtime warming over the same range of years and latitudes.

Springtime provides important biological cues for many plant and animal species, and it is unclear how an accelerated spring could play out for these species across the planet.

The study notes that the impact of an early spring on migratory birds is a potential concern. Many birds move from tropical zones to higher latitudes, such as the Arctic, to breed.

“Whatever cues they’re relying on to move northward for spring might not be reliable predictors of food availability once they get there if the onset of spring at these higher latitudes is amplified by future warming,” Post said.

T.V. Jayan