Shifts in the sea­sons have po­ten­tially dire con­se­quences for finely bal­anced ecosys­tems.

Cosmos - - Climate Watch - JAMES MITCHELL CROW ex­plains.

FOR A FLEET­ING FEW DAYS each year the Ja­panese city of Ky­oto blushes, turn­ing a per­fect shade of pink. Cherry trees burst into blos­som right across Ky­oto, mark­ing the be­gin­ning of spring.

The dis­play will last just a few weeks. Vis­i­tors flock to the city’s an­nual cherry blos­som fes­ti­val both to cel­e­brate Prunus per­fec­tion and to con­tem­plate the fleet­ing na­ture of life. This an­cient cus­tom, and the date each year the blos­som peaks, has been doc­u­mented for more than 1,200 years.

From this re­mark­able data set of spring’s ar­rival a pat­tern emerges. Af­ter fluc­tu­at­ing around April 15 for a mil­len­nia, since 1830 the date of peak blos­som has crept for­ward to April 7.

Spring creep is hap­pen­ing around the globe. The early ar­rival of Ky­oto’s cherry blos­som, while con­spic­u­ous, is hardly the most pro­found ex­am­ple. In the Arc­tic, which is warm­ing more rapidly than other parts of the planet, some plants are awak­en­ing 26 days ear­lier than just a decade ago.

The study of tim­ing pat­terns in the bi­o­log­i­cal world is known as phe­nol­ogy. It has be­come a grow­ing, and fast-mov­ing field, as global warm­ing drives cli­mate change. “A lot of phys­i­o­log­i­cal events in species’ life­cy­cles are cued by tem­per­a­ture thresh­olds,” ex­plains Les­ley Hughes, of Mac­quarie Univer­sity in Syd­ney, who stud­ies the im­pacts of cli­mate change on nat­u­ral ecosys­tems . “Plants and an­i­mals over the past two decades have been re­spond­ing very sen­si­tively to warm­ing.”

Where Ja­pan has its blos­som fes­ti­vals to track the sea­sons, Australia has its vine­yards; as cli­mate crit­i­cally af­fects the qual­ity of a vin­tage, wine mak­ers record it care­fully, cre­at­ing some of the na­tion’s best long-term records of sea­sonal change.

Vines aren’t just awak­en­ing ear­lier in spring; the whole grow­ing sea­son is speed­ing up, says Mardi Long­bot­tom from the Aus­tralian Wine Re­search In­sti­tute (AWRI) in Ade­laide. White grape va­ri­eties used to ripen first, neatly fol­lowed by the reds; these days they are all ripen­ing at once. Part of Long­bot­tom’s work is to help winer­ies man­age the bot­tle­neck. One op­tion be­ing re­searched to de­lay grape ripen­ing is to de­lay vine prun­ing, she says. An­other is to switch to Mediter­ranean va­ri­eties bet­ter suited to warm con­di­tions. As the bush­fire sea­son gets longer, AWRI is also re­search­ing how to min­imise smoke taint flavours in wine.

It’s not just an ecosys­tem’s plants that are af­fected by the shift­ing sea­sons. With spring ar­riv­ing ear­lier and sum­mer lin­ger­ing longer, the ex­ten­sion of flow­er­ing sea­sons and de­lay of au­tumn has con­se­quences for an­i­mals bound to the sea­sonal cy­cle, says Hughes. Mi­gra­tory birds, for ex­am­ple, are ar­riv­ing at their

sum­mer feed­ing grounds ear­lier and stay­ing longer.

A fore­short­ened win­ter may sound like some­thing to cel­e­brate but it can have con­se­quences for nat­u­ral ecosys­tems. Neigh­bour­ing species can re­spond to warm­ing in dif­fer­ent ways, throw­ing in­ter­de­pen­dent species out of sync.

Ver­te­brates are of­ten the most dis­ad­van­taged by these changes, Hughes says. When spring comes early in the Arc­tic, for ex­am­ple, the peak pe­riod of plant growth pre­cedes cari­bou calv­ing sea­son. In years when spring comes early, there is less for the an­i­mals to eat and fewer calves sur­vive.

Even in tem­per­ate climes, mis­matches are emerg­ing. One of the best stud­ied is the re­la­tion­ship be­tween oak trees, win­ter moths and great tits. As the cli­mate warms, the oak leaves are com­ing out ear­lier, and the moth lar­vae that eat the young leaves are hatch­ing ear­lier. But the birds re­spond mainly to day length rather than tem­per­a­ture. Their fledglings are hatch­ing too late to take ad­van­tage of that flush of food avail­able from the win­ter moth, so their pop­u­la­tions are de­clin­ing.

“We’re all ex­pect­ing that, as cli­mate chang­ing is a very strong se­lec­tive pres­sure, there will be some species that will re­spond quite quickly,” Hughes says.

“The prob­lem for the bird, which has a rel­a­tively long life­cy­cle com­pared to an in­sect, is that their ca­pac­ity for evo­lu­tion­ary change is go­ing to be a lot less.”

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