Three peaks in three weeks

Cli­mate change in Aus­tralia’s trop­i­cal cloud forests.

Australian Geographic - - Contents - Story and photography by DEAN MILLER and MARK ZIEMBICKI

An AGS-sup­ported trip to Queens­land’s cloud forests

TORCH BEAMS SCYTHE through the gloom, paint­ing the un­der­side of the rain­for­est canopy above us with bright white light. In­sects buzz, click and hum, frogs croak and creak and tiny bats emit high-pitched squeaks as they flut­ter er­rat­i­cally past. We’re deep in a dense trop­i­cal jun­gle but the night air is cool and mois­ture drips from thick moss on the trees and rocks.

No-one speaks. We’re all weary, hav­ing spent sev­eral nights trudg­ing more than 50km along for­est tran­sects search­ing in vain for our quarry, the rare white form of the lemuroid ring­tail pos­sum. Then, fi­nally, a torch beam comes to rest on a big, fluffy white ball, perched on a branch high in the canopy. Bright-pink nose, large, dark eyes, the pos­sum gazes down at us, ap­par­ently won­der­ing what all the fuss is about.

We’re elated, but the sight­ing is bit­ter­sweet. Cli­mate change has brought this icon of the Wet Trop­ics to the brink of ex­tinc­tion, and as we re­turn its gaze we can’t help won­der­ing how much longer this beau­ti­ful crea­ture will per­sist in th­ese forests.

WE’RE HIGH ON MT LEWIS – an oa­sis of cool in trop­i­cal north Queens­land, and one of the few places in which the white lemuroid pos­sum can be found – as part of an ex­pe­di­tion to climb three of Aus­tralia’s high­est trop­i­cal

moun­tains in three weeks. With support from the Aus­tralian Ge­o­graphic So­ci­ety, our team of re­searchers and ad­ven­tur­ers is hop­ing to gain in­sights into how cli­mate change is af­fect­ing the unique plants and an­i­mals in­hab­it­ing the mys­te­ri­ous cloud forests that drape the sum­mits of th­ese three peaks.

The rain­forests of the Wet Trop­ics are among the world’s most an­cient ecosys­tems. They’re the largest re­main­ing rem­nants in Aus­trala­sia of the great rain­forests that cov­ered the su­per­con­ti­nent of Gond­wana 100–50 mil­lion years ago.Al­though they make up a rel­a­tively small pro­por­tion of Aus­tralia’s to­tal land area, they have the con­ti­nent’s high­est lev­els of bio­di­ver­sity and en­demism.

Like iso­lated is­lands in this vast ocean of rain­for­est, the moun­tain­tops of Mt Bar­tle Frere South Peak (1622m),Thorn­ton Peak (1374m) and Mt Lewis (1224m) sit high above the sur­round­ing low­lands. And, just like many true is­lands, the sum­mits of th­ese peaks are home to nu­mer­ous species found nowhere else, from tiny frogs whose off­spring hatch fully formed from eggs, eschew­ing the tad­pole stage, to a lizard said to be so heat-sen­si­tive it will die if held in your hand for too long.

Th­ese moun­tain tops are also home to some of Aus­tralia’s cloud forests (see box, page 119), gar­dens in the sky with all the beauty and di­ver­sity of their low­land coun­ter­parts with­out the of­tenop­pres­sive heat.Ten­drils of mist float among trees draped in liv­ing cloaks of epi­phytes. Moss and lichen grow on ev­ery avail­able sur­face and ferns sprout from un­likely spots on ground and trees alike.

Sadly, cloud forests are among Earth’s most en­dan­gered ecosys­tems. Trop­i­cal species are in­her­ently vul­ner­a­ble to en­vi­ron­men­tal change be­cause they tend to be rare and oc­cupy small ranges. And, be­cause trop­i­cal en­vi­ron­ments are usu­ally rel­a­tively sta­ble, the species that in­habit them can of­ten only sur­vive within a nar­row range of cli­matic con­di­tions. The moun­tain-top spe­cial­ists are es­pe­cially vul­ner­a­ble be­cause they’re adapted to the cooler, wet­ter con­di­tions found on sum­mits.As the cli­mate warms, th­ese con­di­tions dis­ap­pear, so, if species can’t move or adapt in time, their demise is in­evitable.

Long-term mon­i­tor­ing data have al­ready pointed to sig­nif­i­cant changes in the dis­tri­bu­tions and abun­dance of many bird and mam­mal species in theWetTrop­ics, with up­land en­demics hav­ing un­der­gone the most sig­nif­i­cant de­clines. The lemuroid pos­sum is a case in point. Re­search by Pro­fes­sor Stephen Wil­liams of

James Cook Univer­sity (JCU) in Townsville dur­ing the past 10 years has shown the pos­sum is be­com­ing in­creas­ingly rare. The main rea­son for its de­cline is the in­crease in the in­ten­sity and length of heatwaves in the Wet Trop­ics. In the sum­mer of 2005, max­i­mum tem­per­a­tures were above the pos­sum’s phys­i­o­log­i­cal tol­er­ance for 27 days in a row.With nowhere for the pos­sums to go, many suc­cumbed to the heat, caus­ing the pop­u­la­tion to crash.

THE FIRST OF OUR ‘three peaks in three weeks’ chal­lenge isThorn­ton Peak, about 90km north-west of Cairns. Ris­ing sharply from sur­round­ing low­land rain­for­est, it’s a bea­con dom­i­nat­ing the tourist drive from Cairns to the Dain­tree rain­for­est, its jagged apex of­ten hid­den by cloud and mist.

Reach­ing our camp­site just be­low the sum­mit in­volved 12 hours of bash­ing through dense jun­gle, scram­bling ever up­wards along a steep, barely vis­i­ble trail. Then, sud­denly, we burst from the dark for­est onto a jagged ridge. Just a few hours be­fore, 1000m be­low, we were sweat­ing in the hot, hu­mid sauna of the low­land rain­for­est that sur­rounds the moun­tain’s base. Now, as we stand ex­posed on a se­ries of large gran­ite boul­ders, blasts of cold, mist­laden air sweep over the ridge, chilling us to the bone.

Our team of seven sci­en­tists and ad­ven­tur­ers is hun­gry and ex­hausted but in good spir­its, hav­ing made camp be­fore night­fall. In the fad­ing light, be­tween breaks in the clouds, we glimpse the moun­tain sum­mit we’ve come to ex­plore. Our sur­round­ings seem en­chanted and other-worldly.The eerie, mys­te­ri­ous at­mos­phere hints at the bi­o­log­i­cal riches hid­den here in this unique en­vi­ron­ment.We have four nights to ex­plore the area and hope­fully track down some of the species found only on this peak.

Around us, the for­est is alive with the sounds of crick­ets, frogs, and a trick­ling per­ma­nent creek that runs past our camp.Among the ca­coph­ony, trop­i­cal ecol­o­gist Nadiah Roslan makes out the call of the crit­i­cally en­dan­gered beau­ti­ful nurs­ery frog – one of our pri­mary tar­gets. Found only on this peak above 1100m, it has one of the most re­stricted ranges of any frog in Aus­tralia; the to­tal area of suit­able habi­tat is es­ti­mated to be lit­tle more than 700ha – a third the size of the City of Syd­ney lo­cal gov­ern­ment area.

Species such as this are most at risk from cli­mate change be­cause they’re the least able to adapt or move else­where. They’re also more sen­si­tive to cli­mate change. Steve ex­plains: “Am­phib­ians,

The eerie, mys­te­ri­ous at­mos­phere hints at the bi­o­log­i­cal riches hid­den here.

rep­tiles and in­ver­te­brates are par­tic­u­larly vul­ner­a­ble be­cause they are al­ready close to their lim­its of tem­per­a­ture tol­er­ance.”

TheThorn­ton Peak skink is an­other ex­am­ple. Recorded from only a few lo­cal­i­ties atop this moun­tain, the species can only han­dle a very nar­row range of con­di­tions and it, too, is on the brink of dis­ap­pear­ing.

OUR NEXT DES­TI­NA­TION is Mt Lewis, 50km south of Thorn­ton Peak. As well as host­ing the white lemuroid ring­tail, its up­per reaches are home to the bright blue and red Mt Lewis spiny cray­fish, one of six fresh­wa­ter cray­fish species found in theWetTrop­ics. Liv­ing in cold, fast-flow­ing streams, th­ese cray­fish are only found above 800m. Each moun­tain range has its own species, al­though all are be­lieved to have come from a com­mon an­ces­tor that ex­panded its range into Queens­land more than 5 mil­lion years ago, when tem­per­a­tures were cooler and rain­forests more ex­ten­sive.With nat­u­ral cli­mate change came a con­trac­tion of for­est habi­tat, re­sult­ing in dif­fer­ent moun­tain­top pop­u­la­tions sep­a­rat­ing and evolv­ing into dif­fer­ent species.

Our third and fi­nal peak is Queens­land’s high­est. Mt Bar­tle Frere is among the state’s most pop­u­lar hikes, but when you’re loaded with camp­ing and sur­vey gear it isn’t for the faint-hearted.To make mat­ters worse, in con­trast to con­di­tions on our other as­cents, the day is hot, dry and still.As we climb, it be­comes clear it has been

like this for some time.The drip­ping mosses and ferns that clung to trees and rocks on the other peaks are dry and brown here and leaf lit­ter crunches loudly be­neath our feet. Such con­di­tions are a brief gl­itch for a moun­tain with one of Aus­tralia’s high­est rain­falls, but a timely in­sight into what may lie ahead for th­ese cloud for­est com­mu­ni­ties as dry pe­ri­ods be­come more fre­quent.

After an eight-hour slog, we reach the sum­mit and are re­warded with clear skies and stun­ning views.As we ex­plore the for­est near our camp, a bril­liant golden shape sud­denly flashes be­fore us. Like a scene from a Harry Pot­ter film, a strik­ingly coloured male golden bower­bird ap­pears, as if from nowhere, watches us cu­ri­ously for a mo­ment, then flits off through the dap­pled light of the for­est.

As a high-alti­tude for­est spe­cial­ist, this bower­bird is an­other species that’s un­der­gone a re­cent de­cline in dis­tri­bu­tion and num­bers. We fol­low it as best we can, fum­bling through the un­der­growth, and even­tu­ally stum­ble across a large, elab­o­rate and rather in­con­gru­ous struc­ture. Be­fore us stands the male’s ma­jes­tic bower, an elab­o­rate con­struc­tion of two tow­ers well over a me­tre tall, made from a tan­gle of twigs and adorned with grey-green lichens, flow­ers and fruit. Males build and tend th­ese con­struc­tions with great care, us­ing them to at­tract and woo fe­males.

THE TROP­I­CAL ZONE’S im­por­tance on the global stage is in­creas­ing. By 2050 most of the world’s peo­ple, in­clud­ing al­most two-thirds of its chil­dren, will live in the trop­ics. Trop­i­cal na­tions are also de­vel­op­ing rapidly. Th­ese tu­mul­tuous changes, over­laid by the im­pacts of cli­mate change, sug­gest that what hap­pens in the trop­ics in com­ing decades will have sig­nif­i­cant global im­pli­ca­tions.

While po­lar bears and melt­ing ice caps are of­ten used to high­light the im­pact of cli­mate change on the nat­u­ral world, it’s clear that some of the most sig­nif­i­cant ef­fects are be­ing felt in the trop­ics. Be­cause this re­gion hosts most of the world’s cul­tural and bi­o­log­i­cal di­ver­sity, there’s also much more to lose here. Per­haps, then, the white lemuroid ring­tail pos­sum or golden bower­bird would make bet­ter flag­ship species for high­light­ing the im­pact of cli­mate change – they’re cer­tainly closer to ex­tinc­tion.

Mem­bers of the sci­en­tific sur­vey team hike through alpine grass­lands near the sum­mit of Thorn­ton Peak.

The sur­vey team takes a break among the boul­ders and mist high on top of Thorn­ton Peak. (L–R) Ash­ley Smith, Dr Paul Thue­sen, Dr Mal­colm Brown, Dr Dean Miller, Nadiah Roslan and Ben Flynn.

This rare white form of the lemuroid ring­tail pos­sum is found only above 1000m at a few sites in the Wet Trop­ics. This one was spot­ted on top of Mt Lewis.

A male golden bower­bird dec­o­rates its elab­o­rate bower with fine, small flow­ers on Mt Lewis.

The beau­ti­ful nurs­ery frog, a tiny ground-liv­ing species in the fam­ily Mi­cro­hyl­i­dae, is only found in rain­forests above 1100m on Thorn­ton Peak. It has one of the most re­stricted ranges of any Aus­tralian frog.

Ex­pe­di­tion leader Dean Miller takes in the view across a val­ley near the top of Thorn­ton Peak.

Bi­ol­o­gists Scott Harte, Nadiah Roslan and James Don­ald­son (L–R) in­spect a cam­era trap used to sur­vey wildlife on Mt Lewis.

Spec­tac­u­lar red and blue Mt Lewis spiny cray­fish in­habit the cool, clear moun­tain streams of the three peaks. They can reach up to 30cm in length and live for more than 10 years.

Forests at the top of Thorn­ton Peak (see bot­tom) look more at home in a Tolkien-style fan­tasy than in the trop­ics of north­ern QLD, and of all the peaks sur­veyed, Thorn­ton seemed the most other-worldly. Mosses adorn­ing trees (left) ex­tract mois­ture from the air, driv­ing the cloud for­est sys­tem.

A sun­set view south from Mt Bar­tle Frere, the high­est moun­tain in QLD. Dur­ing our ex­pe­di­tion here the peak was warm and dry and pro­vided in­sight into how th­ese peaks would look if tem­per­a­tures con­tinue to rise and the cloud forests de­cline.

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