"The flowers that bloom in the spring, tra la! That flowers that bloom in the spring!"

It's a lyric from a famous English comic operetta written in the 19th century. But when is the spring? The answer, it seems, is now much earlier than when those lines were written in the 1880s. 

If you have noticed flowers blooming during what we'd normally consider the dead of winter, and little signs of spring blossoming in every green corner, then you're not wrong. Scientists have concluded that global warming is causing spring to move backwards in our calendars at an alarming rate. 

Experts in the UK have compared nature observations dating back to the 1700s and found that the first flowering dates have been progressively going backwards in the calendar, with flowers now starting to bloom 26 days earlier than they used to in the mid-1980s.

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The University of Cambridge academic behind the study defined the results as "truly alarming," saying that the seemingly pleasant early flowering poses a significant ecological threat, especially to wildlife.

Ulf Buntgen, the study's lead researcher and a professor at the University of Cambridge, explained that birds and insects have evolved to synchronize their own development stages with the plants they rely on, and an early blooming could cause a serious "ecological mismatch."

"A certain plant flowers, it attracts a particular type of insect, which attracts a particular type of bird, and so on," said Buntgen.

"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."

If global temperatures continue to increase at the current rates, said Buntgen, spring in the UK could start as early as February. But the scale of the problem might be much bigger than the UK alone: the United Nations confirmed last month that the past seven years have been the hottest on record across the world.

But to truly understand the consequences of climate change on a global scale, researchers need access to much more data, said Buntgen.

"We can use a wide range of environmental datasets to see how climate change is affecting different species, but most records we have only consider one or a handful of species in a relatively small area," said the professor.

For the UK study, Buntgen's team had access to more than 400,000 observations of 406 trees, shrubs, herbs and climbing plants across the country, collected in a database known as Nature's Calendar, which has entries by scientists, naturalists, amateur and professional gardeners, as well as organizations such as the Royal Meteorological Society, going back more than 200 years.   

This data allowed the Cambridge team to identify that the average first flowering date from 1987 to 2019 is 30 days earlier than the average first flowering date from 1753 to 1986. Spring flowers which are normally expected to bloom only later in the year, like daffodils, irises and violets, have been spotted across the UK in January, after a particularly warm start to the year.

An early end to winter may seem like something to sing about, but an early start to spring threatens serious natural disharmony.