The Es­sen­tial For­est

The globe’s bo­real zone is un­der siege. In Canada, home to more than 30 per cent of it, what’s hap­pen­ing in the woods — and what needs to hap­pen? Plus: what YOU can do

Canadian Wildlife - - CONTENTS - By Niki Wil­son

The globe’s bo­real zone is un­der siege. With Canada home to more than 30 per cent of it, here is what is hap­pen­ing, what needs to hap­pen… and what you can do

The North Amer­i­can bo­real for­est is home to some tough char­ac­ters: the elu­sive and fe­ro­cious wolver­ine, the cun­ning wolf and the pow­er­ful griz­zly bear. But one of the tough­est of them all is the bo­real chick­adee. Weigh­ing in at around 10 grams, this small, roundish bird doesn’t fly south when the mer­cury falls but in­stead puffs up its downy chest and takes win­ter on the beak. Stay­ing warm comes at a high en­er­getic cost, though — it must feed daily on food caches to sur­vive, as it lacks suf­fi­cient fat stores to sur­vive pro­longed cold snaps. On chilly win­ter nights, it slips qui­etly into tor­por to con­serve more en­ergy still.

Sure, win­ter is tough, but the bo­real chick­adee can han­dle it. It’s what sci­en­tists call a bo­real-ob­li­gate species — an an­i­mal so highly adapted to habi­tats in the bo­real for­est that it can sur­vive only within them. And for thou­sands of years, it’s been do­ing just fine. How­ever, there’s a wrench in the evo­lu­tion­ary plan. As cli­mate change takes hold, the bo­real is chang­ing — per­haps faster than this tough lit­tle bird can adapt. The past decade has ush­ered in some of the hottest and dri­est con­di­tions on record, and cli­mate models pre­dict tem­per­a­tures will con­tinue to rise. From re­search on the ground to the anal­y­sis of satel­lite images, sci­en­tists are work­ing to un­der­stand the im­pli­ca­tions of these changes for the species that live there.

The bo­real is Earth’s largest for­est, a cir­cum­po­lar ecosys­tem that blan­kets roughly six mil­lion square kilo­me­tres in North Amer­ica — much of Canada and Alaska. Vast tracts of spruce, fir, larch and pine dom­i­nate this great ex­panse, tak­ing up car­bon from the at­mos­phere and pro­vid­ing homes for the bears, wolves, wolver­ine and cougars that weave the deep trees to hunt deer, moose and cari­bou. The melan­choly call of the loon can be heard drift­ing across a mul­ti­tude of lakes across the coun­try. Bo­real toads, beavers and mas­sive flocks of mi­gra­tory birds all de­pend on the wet­lands that also fil­ter wa­ter and hold back floods.

Though we speak of it as one big for­est, the Cana­dian bo­real is made up of eight eco­zones, each of which pos­sesses unique char­ac­ter­is­tics. In some places, sym­phonies of song­birds call from great stands of as­pen, while in oth­ers, stunted spruce grow more sparsely be­fore giv­ing way to the Arc­tic. To un­der­stand how the bo­real for­est is chang­ing is to in­ves­ti­gate in mul­ti­ple places, at mul­ti­ple scales.

Scott Goetz, a pro­fes­sor at North­ern Ari­zona Univer­sity, is the lead sci­en­tist for NASA’S Arc­tic-bo­real Vul­ner­a­bil­ity Ex­per­i­ment, known as ABOVE. One of the many things its

sci­en­tists are study­ing is how bo­real veg­e­ta­tion is chang­ing. For ex­am­ple, how will in­creas­ingly longer fire sea­sons and larger, more se­vere fires change the forests of the fu­ture, and how will that af­fect the car­bon cy­cle?

In a 2015 study, Goetz and col­leagues mea­sured the car­bon emis­sions re­leased from the mas­sive wildlife fires in 2014 in the North­west Ter­ri­to­ries: 2.9 mil­lion hectares burned in what Ernie Camp­bell, deputy min­is­ter of the en­vi­ron­ment and nat­u­ral re­sources for the N.W.T., called “the most in­tense fire be­hav­iour seen by this gen­er­a­tion.” The team es­ti­mated that 94 mil­lion tonnes of car­bon was re­leased into the air — more than half the amount of car­bon es­ti­mated to be taken up by the en­tire Cana­dian bo­real for­est in a year. Though the re­lease of car­bon through fires has been a nat­u­ral part of the Earth’s car­bon cy­cle for thou­sands of years, as the Earth warms, more fre­quent “big fire” years could be­come part of a feed­back loop that am­pli­fies cli­mate change.

It’s not just car­bon emis­sions from fire that can af­fect cli­mate, but how fire changes the land­scape. “What we see in fire-dis­turbed ar­eas, es­pe­cially when they are se­verely burned, is that they switch from be­ing an ever­green for­est to a de­cid­u­ous for­est,” says Goetz. “Gen­er­ally, the more se­vere the fires are, the longer the de­cid­u­ous forests per­sist.” The dark conif­er­ous trees of the bo­real “ab­sorb a lot of en­ergy from the sun, and they hold that en­ergy in a way that’s dif­fer­ent from a de­cid­u­ous for­est,” says Goetz. De­cid­u­ous forests take up more car­bon from the at­mos­phere and also re­flect more sun­light. These changes af­fect the Earth’s en­ergy bud­get — a key driver of cli­mate.

Fire is only one of the symp­toms of in­creas­ing tem­per­a­ture. Drought, in­sect in­fes­ta­tions and dis­ease may also be­come more preva­lent in some ar­eas, con­tribut­ing more sig­nif­i­cantly to tree mor­tal­ity. By study­ing 30 years' worth of satel­lite images doc­u­ment­ing tree growth pat­terns, Goetz and col­leagues have found there are early warn­ings that a for­est is head­ing for this kind of dis­tress. Pat­terns of de­creased growth rate of­ten pre­cede tree death by sev­eral years — even decades. And while some bo­real forests are show­ing in­creased growth rates from re­cent warm­ing, Goetz’s anal­y­sis sug­gests the op­po­site is true for ar­eas in cen­tral Alaska and cen­tral-western Canada, where “it’s pretty clear [growth rate] is de­clin­ing.”

The past decade has ush­ered in some of the hottest and dri­est con­di­tions on record, and cli­mate models pre­dict tem­per­a­tures will con­tinue to rise

Nowhere is this trend more ap­par­ent than at the south­ern edge of the bo­real, where warm­ing is most pro­nounced and the ecosys­tem is the most vul­ner­a­ble. “When you get mul­ti­ple hot years within a decade, you start to see much higher tree mor­tal­ity,” says Goetz.

It’s not just the trees that are los­ing ground. The range of many bo­real-adapted species is re­ced­ing in the south. Ecol­o­gist Den­nis Mur­ray, of Trent Univer­sity, is part of a team of sci­en­tists that re­cently de­vel­oped models to help pre­dict how suit­able cur­rent bo­real en­vi­ron­ments will be for 12 key bo­real-ob­li­gate species, in­clud­ing cari­bou, moose, spruce grouse and bo­real chick­adees, in the next 60 years. Their work shows that most species’ ranges will get smaller and shift north­ward over time, but, says Mur­ray, “There’s an end­point as to how far north [a species’] range can ex­pand.” For ex­am­ple, he says most north­ern soils are not con­ducive to the growth of large trees. “The en­tire for­est will be con­strained in terms of its north­ward mi­gra­tion. Mean­while, south­ern re­ces­sion has no con­straints, so the for­est will shrink over time.”

This squeeze be­tween north and south will be felt more in­tensely in some ar­eas, like what Mur­ray calls the On­tario-que­bec bot­tle­neck, a re­gion that strad­dles the pro­vin­cial bor­der just south of James Bay. “In the fu­ture, that area will be ex­tremely af­fected by cli­mate change, to the point where moose and other an­i­mal pop­u­la­tions will be­come dis­con­nected in that zone.” Some, like the win­ter-hardy bo­real chick­adee, may find that by 2080, there’s no suit­able habi­tat in this re­gion at all.

The bo­real is Earth’s largest for­est, a cir­cum­po­lar ecosys­tem that blan­kets roughly six mil­lion square kilo­me­tres

As crit­i­cal con­nec­tion zones are pinched off, the models pre­dict habi­tat will be­come more frag­mented. “Es­sen­tially, some ar­eas of the bo­real for­est will be­come in­hos­pitable to [most bo­real-ob­li­gate] species, cre­at­ing dis­junct pop­u­la­tions,” says Mur­ray. As bo­real species move out, other species bet­ter adapted to new con­di­tions will move in. “We’re go­ing to see a dra­matic change in species com­po­si­tion.” Mur­ray says we need to con­tinue to in­vest in the col­lec­tion of data to fur­ther re­fine models and bet­ter un­der­stand what will hap­pen at a fine scale.

Ecol­o­gist Erin Bayne, of the Univer­sity of Alberta, agrees. He stud­ies ev­ery­thing from worms to wolves but is known es­pe­cially for his work on how hu­man ac­tiv­i­ties af­fect bo­real birds. He has also helped de­velop models to pre­dict the ef­fects of cli­mate change on the bo­real, some of which he says are “very sober­ing, and very scary.” But he is also care­ful to point out that models have lim­i­ta­tions — they are meant to be used as plan­ning tools, not nec­es­sar­ily the last word. “We are try­ing to iden­tify places on the land­scape that are go­ing to be more re­sis­tant to change,” he says, and with birds, this might mean look­ing in more north­ern lo­ca­tions, in very spe­cific places.

Right now, a lot of the data used to as­sess bo­real bird sta­tus is col­lected in the south­ern part of their range, Bayne says. It’s not good news. “Over the last five years, a num­ber of species that call the bo­real their home have been listed by the Com­mit­tee on the Sta­tus of En­dan­gered Wildlife in Canada as species of con­cern.” These in­clude the Canada war­bler, olive-sided fly­catcher and com­mon nighthawk.

And yet, by look­ing fur­ther north, Bayne and his stu­dents re­cently found what is thought to be one of the largest pop­u­la­tions of com­mon nighthawks in the world. The birds are hun­kered down in a burned area, just north of the oil­sands mines, near Fort Mc­mur­ray, Alberta.

The ques­tion now, he says, is whether or not this group of nighthawks has been in the area for a long time, or if he has found a south­ern pop­u­la­tion that

Snow-melt pools linger in the bo­real for­est near Saska­toon, Saskatchewan. Op­po­site: the hardy bo­real chick­adee

New growth af­ter a for­est fire in NWT. Op­po­site: bo­real fix­tures moose and spruce grouse

Hu­man de­vel­op­ment and re­source ex­ploita­tion is a lead­ing cause of bo­real de­for­esta­tion

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