Re­vealed: why spring is com­ing ear­lier and ear­lier each year ...


Sunday Herald - - 19.03.17 NEWS -

SOON the swal­lows will come swoop­ing back to Scot­land from South Africa, a tra­di­tional sign that win­ter has ended. It may seem as if all is as na­ture in­tended, but it is not. Swal­lows are now ar­riv­ing 20 days ear­lier than they did in the 1970s – and it’s be­cause of global warm­ing caused by cli­mate pol­lu­tion.

It’s not just swal­lows whose habits are chang­ing as tem­per­a­tures rise. A se­ries of sci­en­tific stud­ies have found nu­mer­ous signs that spring – which of­fi­cially be­gins to­mor­row with the ver­nal equinox mark­ing the first day of spring – is com­ing much sooner than it used to.

Orange-tip but­ter­flies are tak­ing to the air 13 days ear­lier than they did a cen­tury ago, while queen wasps are buzzing about six days sooner. Daf­fodils at Nethy Bridge in the Cairn­gorms are flow­er­ing five days ear­lier than they did a decade ago.

Fish and frogs are spawn­ing sooner, trees are bud­ding ear­lier and lawns are be­ing mowed more of­ten. In­sects are ap­pear­ing two weeks ahead of when they did in 1970, while plants are emerg­ing ten days ear­lier.

The im­pacts of ris­ing tem­per­a­tures are not sim­ple and they can vary, but scientists are clear that most signs of spring are ad­vanc­ing. “A warm­ing cli­mate ap­pears to be dis­rupt­ing the se­quence of events that we have grown up with,” said Tim Sparks, pro­fes­sor of en­vi­ron­men­tal change at Coven­try Univer­sity.

“Early nat­u­ral­ists thought there was a nat­u­ral or­der to events. We now know that they were in­cor­rect in this as­sump­tion.”

Sparks pro­vided ev­i­dence on how the av­er­age be­hav­iour of seven se­lected plants and in­sects had changed be­tween 1891-1947 and 2000-2016. Horse chest­nut trees, for ex­am­ple, were now flow­er­ing on April 29 rather than May 6, while hawthorn were flow­er­ing on April 29 rather than May 11.

Ac­cord­ing to the Met Of­fice, the av­er­age spring tem­per­a­ture has risen from 7.1 de­grees be­tween 1961 and 1990 to 8.1 de­grees be­tween 2006 and 2015. Scientists blame the rise on car- bon pol­lu­tion from vehicles, fac­to­ries, farms and homes.

One of the UK’s lead­ing ex­perts on shift­ing sea­sons, known as phe­nol­ogy, is Dr Stephen Thack­eray, from the gov­ern­ment-sup­ported Cen­tre for Ecol­ogy and Hy­drol­ogy (CEH) in Lan­caster. “Over the last few decades many fa­mil­iar UK sea­sonal events, such as flow­er­ing, breed­ing and mi­gra­tion, have shifted ear­lier in the year,” he told the Sun­day Her­ald.

“Many sea­sonal events – our tra­di­tional signs of spring – have changed in as­so­ci­a­tion with chang­ing air and wa­ter tem­per­a­tures. Species have re­sponded very dif­fer­ently over time, and this could af­fect the way in which they in­ter­act with each other.”

Scientists work­ing for the gov­ern­ment Joint Na­ture Con­ser­va­tion Com­mit­tee (JNCC) and CEH have com­piled a “spring in­dex” to show how wildlife is be­ing put un­der pres­sure by cli­mate change. It is based on his­tor­i­cal data, along with ob­ser­va­tions by 50,000 vol­un­teers in re­cent years as part of a ma­jor project called Na­ture’s Cal­en­dar.

The in­dex is founded on four events: the first flow­er­ing of hawthorn and of horse chest­nut, the first recorded flight of an orange-tip but­ter­fly and the first sight­ing of a swal­low. Though tim­ings have Swal­low: ar­rives 20 days ear­lier than in the 1970s Sand martin: ar­rives 25 days ear­lier than in the 1970s Orange tip but­ter­fly: ap­pears 13 days ear­lier than a cen­tury ago Hawthorn: flow­ers 12 days ear­lier than a cen­tury ago Horse chest­nut tree: flow­ers eight days ear­lier than a cen­tury ago

flow­ers five days ear­lier than 10 years ago ap­pears six days ear­lier than a cen­tury ago

spawn ear­lier than they used to ap­pear 10 days ear­lier than in 1970 var­ied over the years, it sug­gests that since 1999 the an­nual av­er­age dates for these events have been six days ear­lier than they were in the first part of the 20th cen­tury.

The JNCC’s bio­di­ver­sity in­di­ca­tors man­ager Dr James Wil­liams noted that the spring in­dex ad­vanced more rapidly when the av­er­age tem­per­a­ture in March and April was seven de­grees or higher. Com­plex changes could harm some species, he sug­gested.

“Dif­fer­en­tial re­sponses among species may cause prob­lems for life cy­cles such as pol­li­nat­ing in­sects emerg­ing out of syn­chrony with flow­ers open­ing in spring,” he said. “This could in­crease vul­ner­a­bil­ity to ex­treme events such as late frosts, dis­rupt food webs, and change the bal­ance of com­pe­ti­tion be­tween species.”

Na­ture’s Cal­en­dar has also pro­vided ev­i­dence that spring is mov­ing faster from south to north every year. In 2015 spring took nearly three weeks to travel from the far south west of Eng­land to the far north east of Scot­land, trav­el­ling at about three kilo­me­tres an hour. Be­tween 1891 and 1947, it moved north at 1.9 kilo­me­tres an hour.

Na­ture’s Cal­en­dar is co­or­di­nated by the con­ser­va­tion charity The Wood­land Trust. “We be­lieve cli­mate change is the big­gest sin­gle threat to what lit­tle re­mains of our an­cient wood­land her­itage,” said the trust’s spokesman in Scot­land, Ge­orge An­der­son.

“The more data we can col­lect, the more ev­i­dence we will have that cli- mate change is a prob­lem, as there are those who still need con­vinc­ing.”

The more in­for­ma­tion the trust gath­ered, the bet­ter it could also man­age the im­pact of cli­mate change, An­der­son ar­gued.

“Our Na­ture’s Cal­en­dar vol­un­teers make a valu­able con­tri­bu­tion to un­der­stand­ing cli­mate change and to pro­tect­ing species from it.”

ROY Turn­bull, a nat­u­ral­ist in the Cairn­gorms, has been chart­ing changes at Nethy Bridge in Strath­spey since the 1980s. There, av­er­age March tem­per­a­tures have been ris­ing by 0.7 de­grees a decade, he said. Frogs are spawn­ing 1.3 days sooner every 10 years, while bum­ble­bees are ap­pear­ing 1.3 days ear­lier and wood anemone flow­er­ing two days ear­lier. Turn­bull has seen sil­ver birch leaves grow­ing 7.4 days sooner every decade, and the first daf­fodils 4.8 days ear­lier.

Friends of the Earth Scot­land high­lighted the need to do more to cut car­bon pol­lu­tion. “Na­ture is send­ing us very clear sig­nals that the cli­mate is chang­ing and that ma­jor dis­rup­tion is on the way,” said the en­vi­ron­men­tal group’s di­rec­tor, Dr Richard Dixon.

“No one can deny there is a big prob­lem. We need to work much harder to re­duce cli­mate change emis­sions from fac­to­ries, traf­fic, farm­ing and homes if we are to save our pre­cious wildlife and, ul­ti­mately, our own so­ci­ety.”

Daf­fodil: Queen wasp: Perch: Plants:

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