Global Warming and Canada's Forests: from Impacts to Adaptation

8/3/2019 Global Warming and Canada's Forests: from Impacts to Adaptation

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climate change and canadas forests

rom impact s to adaptation

t. B. W ll , n u l re u e c , c e se e

s. J. c l b , o m y n u l re u e

p. n. du ke , s h l re u e E e l s u e , d lh u e U e y

p. a. G y, o m y n u l re u e

r. J. He e ey, s h l re u e E e l s u e , d lh u e U e y

d. H ule, m e e re u e n u elle e e l u e u Qube / ou

m. H. J h , s k hew re e h c u l

a. E. og e , Yuk e m ge e B h

d. L. s leh u e, B h c lu b m y e r ge


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Her Majesty the Queen in Right o Canada, 2009

This publication is available at no charge rom:

Natural Resources Canada Sustainable Forest Management NetworkCanadian Forest Service 3-03 Civil Electrical Engineering Building

Northern Forestry Centre University o Alberta5320 122 Street Edmonton, AlbertaEdmonton, Alberta T6G 2G7T6H 3S5

For an electronic version o this report, visit the Sustainable Forest Management Networkwebsite at http://s mnetwork.ca/ or the Canadian Forest Service Bookstore athttp://bookstore.c s.nrcan.gc.ca/

Cette publication est galement disponible en ranais sous le titre Les changements climatiques et les forts du Canada : des impacts ladaptation

TTY: 613-996-4397 (Teletype or the hearing impaired)

Library and Archives Canada Cataloguing in Publication

Climate Change and Canadas Forests: Current and Future Impacts / T. Williamson [et al.].

Electronic monograph in PDF ormat.Co-published by: Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre.Includes bibliographical re erences.Issued also in printed orm.Catalogue No. Fo134-9/2009E-PDFISBN 978-1-55261-205-7

1. TreesE ect o global warming onCanada. 2. Forest productivityClimatic actorsCanada 3. Climatic changesCanada. 4. Climatic changesCanadaForecasting.5. Forests and orestryCanada. 6. Global warming. 7. Forest managementCanada.I. Williamson, Timothy Bruce, 1953- II. Northern Forestry Centre (Canada) III. SustainableForest Management Network

SD145.C54 2009 634.9610971 C2009-980039-X

Photo credits: Front cover (left to right) : Natural Resources Canada, Yukon ForestManagement Branch, Parks Canada, R. Parsons. Back cover (left to right) :M. Michaelian, R. Parsons, M. Michaelian, Ontario Ministry o NaturalResources. Pages xvi, 53 : Yukon Forest Management Branch. Pages xvii,48 : D. Brook. Page 4 : Forest fres and smoke, Parks Canada; Winter

harvesting problems, The Forestry Forum (www. orestry orum.com), Winddamage, Kyle Mackenzie; Wind throw/blow down, Peter Duinker. All otherphotos belong to the authors or their respective institutions.

Please cite this report as: Williamson, T.B.; Colombo, S.J.; Duinker, P.N.; Gray, P.A.;Hennessey, R.J.; Houle, D.; Johnston, M.H.; Ogden, A.E.; Spittlehouse, D.L. 2009. Climatechange and Canadas orests: rom impacts to adaptation. Sustain. For. Manag. Netw. andNat. Resour. Can., Can. For. Serv., North. For. Cent., Edmonton, AB. 104 p.


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FOREWORD

Recent events indicate that climate change is already having a signi cant impact onCanadas orests. These unprecedented events include the severe 2003 and 2004 re

seasons in British Columbia and the Yukon, the recent national drought, the mountainpine beetle epidemic, and reduced winter harvest opportunities being experienced inmany areas. Future climate change has the potential or more pronounced impacts on thecapacity o our orests to provide the many goods and services we value them or. Forestmanagers will experience the impacts rst-hand and they need the best in ormationavailable on what climate change means to them so that they can develop and implementadaptation measures.

The Sustainable Forest Management Network and Natural Resources Canada / CanadianForest Service are pleased to collaborate on Climate Change and Canadas Forests: FromImpacts to Adaptation. Based on the work o the orestry authors o the recently releasedCanadian national assessment 1, this report summarizes the current state o knowledge ocurrent and uture impacts o climate change and its implications or orest management.

Innovative research and knowledge exchange are essential or Canadas orest industry asit adapts to a changing climate. The Sustainable Forest Management Network and NaturalResources Canada / Canadian Forest Service are committed to providing orest managerswith timely research ndings about the implications o climate change on our ability tosustainably manage Canadas orests.

Tim Sheldan Dr. James FylesDirector General McGill UniversityNorthern Forestry Centre Scienti c DirectorCanadian Forest Service Sustainable Forest Management NetworkNatural Resources CanadaEdmonton, AB

1 from imp ts to ad pt t on: c n d n ch ng ng cl m te 2007 h :// . .g . / e /2007/ e _e. h

c L i m a t E c H a n G E a n d c a n a d a s o r E s t s


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AbstRACtClimate change is already a ecting Canadas orests. Current visible e ects includechanges in the requency and severity o disturbances (such as res, drought, severestorms, and damaging insect and disease attacks): other less visible changes such aschange in the timing o spring bud burst are also underway. One o the consequences o

uture climate change will be urther increases in the requency and severity o extremeweather events and disturbances. Changes in productivity, species composition, andage- class distribution are also expected. Moisture and temperature are key actorsa ecting productivity. Productivity is likely to decrease in areas that are now or willbecome drier; productivity is expected to increase (at least in the near term) in northernareas that are currently limited by cold temperatures. An important consideration,however, is that genotypes tend to be nely adapted to local climates and potentialproductivity gains may not be realized i orest managers dont match genotypes tosuitable climates. A higher percentage o the orests will be in younger age classes, andthe requency o early succession species and species adapted to disturbance willincrease. Climatically suitable habitats or most species will move northward and willincrease in elevation but the actual movement o species will lag behind the rate omovement o climatic niches. Climate change has implications or both current and uturetimber supply. The net impact o climate change on timber supply will vary rom locationto location. The recent mountain pine beetle event shows that climate-related actors canhave dramatic e ects on timber supply in a relatively short time period. Climate changewill impact harvest operations. A signi cant portion o the harvest in Canada occurs in thewinter when the ground is rozen. Harvesting on rozen ground allows or access towetlands, reduces soil disturbance, and decreases costs o delivered wood. Themagnitudes o change in climate that will be aced by Canadas orests and orestmanagement sector and the consequent scale o expected impacts have no historicalanalogue. Canadas orest sector will need to adapt and it will need to do so without thebene t o prior experience. Forest managers can expect the unexpected and they canexpect that change will be ongoing and unrelenting. Some general recommendations orbeginning to address climate change in Canadas orest sector include enhancing thecapacity to undertake integrated assessment o vulnerabilities to climate change atvarious scales; increasing resources to monitor the impacts o climate change; increasingresources or impacts and adaptation science; reviewing orest policies, orest planning,

orest management approaches, and institutions to assess our ability to achieve socialobjectives under climate change; embedding principles o risk management and adaptivemanagement into orest management; and maintaining or improving the capacity orcommunicating, networking, and in ormation sharing with the Canadian public andwithin the orest sector.


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RsumLes changements climatiques a ectent dj les orts du Canada. Les e ets actuels lesplus visibles prennent la orme dune modi cation de la rquence et de la gravit desperturbations ( eux, scheresses, temptes violentes, in estations dinsectes et maladies).Mais dautres changements moins vidents sont dj prsents, notamment dans lapriode de dbourrement au printemps. Lune des consquences des changementsclimatiques venir se prsentera comme une augmentation supplmentaire de la

rquence et de la gravit des drglements et des mani estations extrmes desconditions mtorologiques. On sattend galement des changements dans laproductivit et la composition orestire et dans la distribution des classes dge.Lhumidit et la temprature sont des acteurs cls de la productivit. On sattend ce quela productivit diminue dans les zones qui sont dj sches ou qui le deviendront, maisquelle augmente (du moins court terme) dans les zones nordiques o les tempratures

roides sont actuellement des acteurs limitants. Il est cependant important de tenircompte du gnotype qui a tendance tre troitement adapt au climat local. Les gainsde productivit potentiels pourraient donc ne pas se raliser moins que les amnagistes

orestiers ne assent correspondre le gnotype au climat appropri. Les ortscomprendront une proportion accrue de jeunes classes dges, dessences pionnires etdessences adaptes aux perturbations. Les habitats convenant la plupart des essencessur le plan climatique vont se dplacer vers le nord et vont monter en altitude, mais ledplacement rel des essences sera retard, car il ne pourra suivre le rythme dedplacement des niches climatiques. Les changements climatiques ont galement desrpercussions sur lapprovisionnement orestier, actuel et utur, mais le rsultat netvariera dun endroit lautre. Le phnomne rcent du dendroctone du pin ponderosadmontre que les acteurs relis au climat peuvent avoir des e ets considrables surlapprovisionnement en bois dans une priode relativement courte. Les changementsclimatiques vont avoir un impact sur les oprations dexploitation orestire. Une partieimportante de la coupe au Canada se ait en hiver quand le sol est gel. Ce procdpermet laccs aux zones humides, rduit la perturbation du sol et diminue les cots detransport du bois. Lampleur des changements climatiques auxquels devront aire ace les

orts et le secteur orestier du Canada, ainsi que ltendue des impacts prvus, nontaucun analogue dans lhistoire. Le secteur orestier du Canada devra sadapter et il devrale aire sans lavantage dune exprience antrieure. Les amnagistes orestiers doiventprvoir limprvisible et sattendre ce que les changements soient continus et sepoursuivent sans relche. Le rapport prsente quelques recommandations gnralescomme premier pas dans la lutte contre les changements climatiques dans le secteur

orestier du Canada, notamment amliorer les capacits permettant dentreprendre di rentes chelles des valuations intgres des lments de vulnrabilit devant leschangements climatiques; augmenter les ressources a ectes la surveillance desimpacts des changements climatiques et celles qui sont destines la recherchescienti que sur limpact et ladaptation; rexaminer les politiques orestires, laplani cation orestire, les approches damnagement orestier, ainsi que les institutionspour dterminer si nous sommes en mesure de raliser des objecti s sociaux compte tenudes changements climatiques; enchsser les principes de gestion du risque et de gestionadaptative dans lamnagement orestier; et prserver ou amliorer les capacits decommunication, de rseautage et de partage de lin ormation avec tous les intervenants,notamment la population canadienne et les milieux orestiers.


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Acknowledgments

The authors thank the Sustainable Forest Management Network (Networks o Centres o

Excellence) or their contributions to the production o this report, which are toonumerous to mention. The authors also thank Don Lemmen (Natural Resources Canada)or his support o this project and or working with them to ensure consistency with the

national assessment report. Kelvin Hirsch (Canadian Forest Service) had the initial idea ocombining the orestry author contributions to the national assessment into a orestryassessment and the authors thank him or that as well as or numerous other suggestions.Dr. Gordon Miller (Canadian Forest Service) oversaw management aspects and providedhelp ul eedback. A number o people provided help ul comments on the content o thereport, including David Price (Canadian Forest Service), Dominique Blain (EnvironmentCanada), Santiago Olmos ( ormerly o the Canadian Forest Service), Catherine Ste.-Marie(Canadian Forest Service), and Shelley Webber (Canadian Forest Service). The authors

thank Brenda Laishley (Canadian Forest Service), Denis Rochon (Canadian Forest Service)and Jenni er Thomas or editorial assistance. They also thank the technical reviewers:Steve McNulty (USDA Forest Service), Rich Fleming (Natural Resources Canada, CanadianForest Service), and Nancy Kingsbury (Natural Resources Canada, Canadian ForestService) or their help ul, constructive, insight ul, and valuable comments andsuggestions.


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t a B L E

o f

c o n t E n t s

Foreword

AbstrAct

rsUm Acknowledgments

execUtive sUmmAry

chApter 1 introdUction 1

chApter 2 cUrrent impActs on cAnAdAs Forests 3ob e e h ge g w g e , he l gy, ee l e the 20012003 ugh i e e e f e y

m u e bee le s u e b k bee le d h ee le bl gh i l

chApter 3 FUtUre impActs on cAnAdAs Forests E e e we he l b l y

e f e i e e e u b e E e hy l g l e e p u y

c , bu , u u e c e e ecl e- e e z e the b e l e U e y su y 26

chApter 4 regionAl Forest vUlnerAbilities 29the n h 29B h c lu b p e e o

Quebe 38a l c

chApter 5 impActs on the Forest sector 41e ge e e e e u y e -b e u e e -b e ubl - e y g e e


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chApter 6 conclUsion And recommendAtions 53G w g w e e 53ch e z g he l e h ge c e

e e 54a 55c lu 57re e 59

reFerences 63

list oF tAbles And FigUres gu e 1. reg l l e h ge c e 4 gu e 2. a l e h ge e 10 gu e 3. cl e h ge he e e 42 t ble 1. a u y ble c e

ge e 58


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The orest sector in Canada is vulnerable to climate change, because o the expectedmagnitude o climate change at Canadas northern latitude, the sensitivity o Canadas

orest ecosystems to climate change, the long growing cycles o trees and the importanceo orests and the orest sector to Canadians. The purpose o this report is to providein ormation to orest managers to assist them in identi ying and assessing potentialimpacts o climate change and requirements and options or adaptation. The report isbased on contributions by the authors to the orestry sections o the recent Canadiannational assessment report titled From Impacts to Adaptation: Canada in a ChangingClimate 2007. 2

i a a a ca a a Climate change is already a ecting Canadas orests. The most visible impacts are in the

orm o changes in the requency and severity o disturbances (such as res, drought,severe storms, and damaging insect and disease attacks). For example, the currentunprecedented outbreak o the mountain pine beetle in British Columbia and Alberta, therecent spruce bark beetle outbreak in the Yukon, the dothistroma needle blight outbreak innorthwestern British Columbia, aspen dieback in the Prairies, unprecedented levels o reactivity in the western boreal orest, and the recent occurrence o record orest reseasons in the Yukon and British Columbia have been linked, at least in part, 3 to recentclimate change. Much more subtle e ects are also being observed. For example, thelength o the growing season is increasing, bud burst in sugar maple is occurring earlier,the fowering period o aspen is occurring earlier, and tree lines are moving upward inelevation. These examples show that impacts o climate change are already occurring and

they provide a basis or beginning to understand how uture climate change will a ectCanadas orests.

Extreme weather and climate

Canadas climate will continue to change over the next 100 years and the rate o change isexpected to be substantially higher than that over the previous 100 years. One o theconsequences o ongoing climate change will be urther increases in the requency andintensity o extreme weather and climate. For example, the length, requency, andseverity o drought events will likely increase; this will have major consequences or

2 see Le e , d.s.; W e , .J.; L , J.; Bu h, E., e . 2008. : c l e 2007. G e e c , o w , on. a l ble :

(E gl h) h :// . .g . / e /2007/ e _ . h > ( e h) e e 12 aug. 200

3 i bu e l e h ge e e he e ul ul le e g u ge le, h bee ugge e h e u l u e e , f e u e , e ge e

el ely e e - ge l ge le e e e l B h c lu b e by he ge l e hu e ble he u e bee le. re e l e h ge e ul e ge e he bee le

b e h e bu e he u b e k.

E x E c U t i v E s U m m a r Y


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orests across Canada but particularly in areas that are already moisture limited such asthe southern interior o British Columbia and the southern boundary o the boreal orestin western Canada. Windstorms and intense precipitation events are expected to increasein requency and intensity, resulting in an increase in blowdown and food risk.

Forest fre

Climate change will signi cantly increase orest re activity. Researchers have ound thatthe average annual area burned nationally could increase by 74% to 118% over currentvalues by the latter part o this century. There is, however, wide variation in the extent towhich re activity is expected to increase in di erent regions. For example, the rate oincrease in re activity will be lower in Atlantic Canada and in the moister eastern portionso the boreal orest whereas it will be higher in the orests o western Ontario andwestern Canada.

Insects and disease

Insects and disease are important agents o change and renewal in orests. They can alsobe highly destructive during outbreaks. Climate is a key actor a ecting the requency,intensity, and duration o outbreaks and also the geographic range o particularspecies. The response to climate change will vary rom species to species;however, or insects and diseases as a group, climate change will almostcertainly result in more requent, more widespread, more intense, and longerlasting outbreaks that in turn have the potential or signi cant negative impactson host tree species that may already be stressed by altered climatic regimes.Insect species with the potential or increased economic impacts under climatechange include the mountain pine beetle, the larch sawfy, the spruce bark

beetle, the jack pine budworm, the spruce budworm, the gypsy moth, the oresttent caterpillar, and the large aspen tortrix. Climate change is also likely toincrease the risk that exotic insects and diseases will become established inCanadian orests.

Disturbance interactions

Climate change may result in multiple, interacting disturbances that occur simultaneously,with impacts beyond those o single disturbances. For example, insect and diseasedamage can result in an increase in wild re risk, or events like drought can put stress ontrees, making them more susceptible to insects and disease attack. These interactions are

complex and di cult to predict. They are, however, potentially signi cant.

Productivity

The net e ects o climate change on productivity will vary rom location to location andover time. Temperature, moisture, nutrient availability, and atmospheric CO 2concentrations a ect rates o photosynthesis and respiration, phenology, reproduction,growth, and mortality; all our o these actors are expected to change with changes inclimate. Productivity is likely to decrease in areas that are now or will become moisturelimited; it is expected to increase (at least in the near term) in northern areas that arecurrently temperature limited (assuming moisture and nutrients are not limiting). An


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additional consideration with respect to the e ects o climate change on productivity isthat genotypes tend to be nely adapted to local climate. A change in the climate o anarea may result in a situation in which local genotypes become maladapted to the newclimate. New trees that become established at a site that are progenies o trees that haveadapted to the areas historical climate may have reduced productivity under a newclimate (or may not be able to exploit potential productivity gains). A potentialmanagement response could be to redistribute genotypes through seed trans ers tobetter match genotypes to the uture expected climate at particular sites. The implicationis that in the case o renewed stands where productivity gains are possible, such gainsmay be contingent on a human management response in the orm o seed orseedling trans ers.

Composition, distribution, and structure o Canadas orest ecosystems

Over time, climate change will result in changes in species composition and distribution,age-class distributions, and orest structure. These changes will occur gradually and they

will be driven by several processes, including the ollowing: physiological e ects; thedevelopment o new conditions a ecting relativecompetitive successes o plants that are native to an area;invasion o new species; di erences in the abilities oindividual species to acclimatize, adapt, or migrate; andchanges in spatial and temporal patterns o disturbance.Forests will likely become younger over time and the

requency o early succession species and species adaptedto disturbance (e.g., jack pine) will increase. Climaticallysuitable habitats or most species will move northwardand will increase in elevation but the actual movement o

species will lag behind the rate o movement o climatic niches. There are our mainreasons that species change will not keep pace with change in climatically suitablehabitats. First, the rate at which species can migrate is generally ar lower than the rate atwhich new climatically suitable areas will develop. Second, even though a new speciesmight be avored at a particular location under a new climate, the current species has theadvantage o site occupation, resulting in a lag be ore the new species will be able tooccupy the site. Third, species o ten do not unction independently within an ecosystem.They require other species to conduct certain processes or provide certain unctions orprepare the site in a certain way. Fourth, new climatically suitable areas may not beedaphically suitable (i.e., soil conditions may notbe suitable).

White spruce and black spruce are important species in much o Canadas boreal orest. Anumber o studies suggest that these species may be a ected negatively by climatechange, resulting in a reduction in their net aerial coverage over time. Studies simulatingthe e ects o climate change on jack pine have had mixed results. Jack pine responds

avorably to increases in temperature and increases in spring precipitation but isnegatively a ected by increases in snowpack. Jack pine has adapted to orest re and issuccess ul on dry sites; it is likely to be avored by increases in re disturbance and inareas that become warmer and drier. This potential spread o jack pine could, however, becounteracted by losses to the mountain pine beetle i the beetle spreads eastward into theboreal orest.

climate change will result inchanges in species compositionand distribution, age-class distributions, and orest structure.


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r a u a

The North

The boreal orest o the Yukon and the Northwest Territories comprises about 13% oCanadas total orest cover. Climate is expected to change much more signi cantly in the

North than at southern latitudes. Signi cant impacts on northern orests are anticipated.The most signi cant impacts will occur as a result o northward movement o the tree line,increases in orest re disturbance, and melting o large areas o perma rost (withnegative consequences or the northern orest). The resulting changes in orests will haveimpacts on commercial orestry operations in the North, on subsistence activities, and ontraditional and cultural values. For example, increases in wild re activity may improve thesupply o mushrooms but will also probably have negative impacts on woodland caribou.

British Columbia

British Columbia is both a coastal and a mountainous province. The provinces climate

varies widely and the terrain is diverse. British Columbia has the most productive andecologically diverse orests o any province in Canada. The province is also Canadaslargest producer o wood products. British Columbia was the rst province to experiencea major event related to climate change: the mountain pine beetle outbreak. The mainsources o vulnerability to climate change or British Columbias orests and orest sectorover the next 50 years are as ollows: restructured global markets with implications orBritish Columbias exports, increased re disturbance, increased losses rom insectdamage and disease, increased requency and intensity o droughts in the southerninterior portions o the province that are currently drought prone, species migration andchanges in orest productivity, and loss o habitat in high-elevation orests.

Prairie provinces

The boreal orest is the dominant orest ecosystem in the Prairie province region. Asigni cant portion o the western Canadian boreal orest could become exposed to drierclimate, similar to that in the present aspen parkland zone. Forest res are also expectedto be more requent, to be o higher intensity on average, and to burn over larger areas.Also, the re season will become longer. Insect outbreaks are also expected to be more

requent and more severe. The combined e ect o increases in orest re, drought, andinsect disturbances will lead to increased tree mortality, a younger orest, a shi t towardpioneer tree species, and a loss o some orest areas. For example, over time, continuous

orests at the southern boundary o the boreal orest will convert to aspen parkland and

what is currently aspen parkland will convert to prairie grassland type ecosystems.

Ontario

One o the most signi cant sources o the vulnerability o Ontario orests to climatechange is an increase in the requency and intensity o disturbances. The overall areaburned is projected to increase by between 50% and 300% by 2080, with most o theincrease occurring in the remote northwestern portions o the province. Climate change isexpected to result in increased spruce budworm damage in northern areas o theprovince and decreased budworm damage in southern areas. Warming will permit


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expansion o the northern range limit o many species; however, actual species migrationwill not keep pace with the rate at which climatically suitable niches expand. In the longterm, species common to the temperate deciduous orest o southern Ontario (e.g., sugarmaple, red maple, white pine) may migrate northward into what is currently boreal orest(subject to availability o edaphically suitable sites). However, such changes may takemany hundreds o years. Thus, the only signi cant changes in tree species compositionattributable to climate change in the near term will be changes in the relative abundanceso species that are already present in particular areas. Climate change will avordisturbance-adapted species more than has been the case under Ontarios historicalclimate. This will likely contribute to an increase in the relative abundance o species suchas jack pine, black spruce, white birch, and aspen. For areas that become drier, drought-tolerant species such as jack pine and aspen will be avored at the expense o species suchas black spruce and balsam r. In the Great Lakes St. Lawrence orests there may beepisodes o drought that lead to early stand dieback and breakup. In these ecosystems,xeric species (i.e., species adapted to dry conditions) such as red maple, white pine, andred oak will be avored over mesic species (i.e., species adapted to moist conditions) such

as sugar maple and eastern hemlock.

Quebec

Three large orest ecozones comprise Quebecs orested landscape. From south to north,these are maple orest, r orest, and spruce orest. Climatic zones or these ecozones areexpected to move approximately 500 km to the north by 2050, which represents a rate oapproximately 10 km annually. As noted, this rate is much higher than the astestobserved migration speeds o trees. Moreover, given the di erent methods and rates odispersal among species and the di erences in the physiological responses o species tochanges in climate, species will migrate at di erent rates. This is likely to result in species

assemblages that have previously not been experienced. Quebecs orests will also bemodi ed by changes in disturbance. For example, the ollowing changes in insectdisturbance are anticipated: the range o the spruce budworm could increase signi cantlyand outbreaks may last longer and cause greater de oliation; the range o gypsy mothmay expand, threatening the hardwood orests o southern Quebec and urban orests;and the Asian long-horned beetle could expand its range into areas currently occupied bymaples, elms, and poplars. In terms o orest re, the requency o wild res is expected toincrease in Quebecs western and northern regions, decrease in the east, and remainconstant in the center o the province. The thinning o snow cover and early melt o snowcover are sources o concern or orest managers in southern Quebec orests. Soilexposed to open air exposes roots to reezing. Freezing at the root layer o trees in this

region causes substantial root damage, which can signi cantly a ect growth or a numbero years.

Atlantic Canada

There are two major orest types in Atlantic Canada: the Acadian orest (which stretchesacross the Maritime provinces o Nova Scotia, New Brunswick, and Prince Edward Island),and the boreal orest (located in New oundland and Labrador). The distribution o nativespecies in Atlantic Canadas orests is expected to shi t with uture climate change. Treespecies that may have di culty persisting under a changing climate may drop out (e.g.,


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balsam r), whereas those able to persist will dominate. Because tree-species migrationis such a slow process, an infux o tree species common to the Carolinian orest o thenortheastern United States is unlikely to occur during the 21st century unless assistedthrough planting programs. Insects are a primary cause o disturbance to both theAcadian and the boreal orests o Atlantic Canada. Spruce budworm in particularrepresents a signi cant source o orest disturbance. Other species that will contribute tothe vulnerability o Atlantic Canadian orests in the uture include the spruce beetle andthe hemlock woolly adelgid. The ormer is an opportunistic native species that takesadvantage o windthrown trees. The latter species, currently excluded rom AtlanticCanada by winter temperatures, may capitalize on moderate winters and could alter thecomposition o Atlantic Canadian orests by killing the eastern hemlock component oAcadian orests as it has done in the United States. Given the mild and wet conditionsprevalent in Atlantic Canada, drought is considered a comparatively minor orce odisturbance. Less than 1% o the total orested area o the Atlantic Canadian provinceswas burned in 2005. Given the current direct contribution o re to the overall disturbanceregime o Atlantic Canada and the overall wetter conditions predicted or the region in a

uture climate, re itsel will not likely become a matter o increased concern. Acadianorests are, however, subject to damage by wind. Wind is also a major disturbance regimein the orests o Labrador and on the island o New oundland. The predicted warming othe north Atlantic may result in an increase in the severity and requency o severeweather. Atlantic Canadian orests will there ore become vulnerable to large-scalewindthrow, especially in coastal regions.

i a Forest management

Most (94%) o the orest land in Canada is under public ownership. Timbersupply on public orest lands is generally described by measures such as theallowable annual cut and the long-run sustainable yield. Climate change hasimplications or both current and uture timber supply. The net impact o climatechange on timber supply will be determined by how climate a ects a number ointerrelated actors, including the impacts o climate change on orest land area,growth rate, disturbance patterns, management inputs, regulatory constraints,regeneration success, and species composition. At local scales, changes intimber supply may be positive or negative, depending on location, time rame,and human adaptation to the e ects o climate change. It is not possible at thistime to estimate the impacts o climate change on timber supply nationally. Itmerits noting, however, that the national so twood allowable annual cut rom provincialpublic lands in 2004 was around 159 million m 3 whereas the actual harvest o so twood

ber was between 140 and 150 million m 3. Thus, any signi cant reductions in so twoodallowable annual cut would likely translate into reductions in harvest with associatedreductions in production, exports, incomes, taxes, and employment.

Climate change may also have an impact on Canadas ability to achieve objectives orsustainable orest management. The Canadian Council o Forest Ministers has developeda ramework that de nes sustainable orest management and provides a basis ormeasuring progress toward it. The ramework is based on six criteria. The criteriarepresent important classes o values that Canadian society associates with orests and


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orest management: biological diversity, ecosystem condition and productivity, soil andwater, role o orests in global ecological cycles, economic and social bene ts, andsocietys responsibility. The ramework also includes a set o indicators or measures thatassess Canadas per ormance in providing a socially desired level o bene ts or eachcriterion. Climate change, which is beyond the control o the Canadian orestmanagement sector, has the potential to negatively a ect each o these classes o valuesand many o the measures that are currently used to measure Canadas per ormance insustainable orest management.

Forest operations

A signi cant portion o the harvest in Canada occurs in the winter when the ground isrozen. Harvesting on rozen ground allows or access to wetlands, reduces delivered

wood costs, and reduces soil disturbance. On the basis o projections or warmer wintersand more precipitation in the uture, the time window when rozen-groundconditions exist will shorten. This is a potentially large problem in many boreal

orest regions, because some orest management agreement areas can consisto up to 40% wetlands. Forest companies have ew options to deal with thedecrease in rozen-ground conditions. In the short term, more harvesting can bedone on summer ground, but eventually timber supply in summer-access areaswill run out. Some have suggested building more permanent roads, but theseare expensive. In addition, the current provincial orest management policy inmany jurisdictions is to minimize permanent road construction and torehabilitate temporary roads once harvest activities are complete. Specializedequipment (e.g., high-fotation tires) is available but it is expensive and can onlybe used or a short time each year. In addition, some o these technologies

require additional maintenance. This also adds to costs.

Forest industry

In addition to being potentially a ected by changes in timber supply and changes indelivered wood costs, the Canadian orest industry will potentially be a ected by changesin global markets resulting rom climate change. Canada is the worlds leading exporter o

orest products. Research shows that climate change will increase global timber supply.Some countries will gain more than others and this will lead to shi ts in the comparativeadvantages o exporting countries. Climate change is expected to reduce the economicbene ts o the trade in orest products or North American producers. This reduction isexpected to be signi cant in the early part o the century, as a result o a decline in relative

prices and in relative market share by North American producers.

Forest-based communities

The impacts o climate change will probably not be evenly distributed across Canadiansociety. Some segments o Canadian society are relatively more vulnerable because otheir location, their strong association with climate-sensitive environments, or theirparticular economic, political, and cultural characteristics. Rural, resource-basedcommunities are o particular concern. Forest-based communities ace the same kinds oimpacts and risks associated with climate change that non- orest-based communities ace.


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These include potential health e ects (e.g., heat stress, e ects on air and water quality,increased exposure to insects and diseases), impacts on in rastructure (e.g., roads,sewers, building heating and cooling needs), and exposure to extreme weather events(e.g., foods and storms). However, orest-based communities ace a number o additionalrisks that will magni y their vulnerability to climate change. First, residents o orest-basedcommunities have strong ties to the surrounding climate-sensitive orest landscape.Second, residents in orest-based communities (particularly communities that closelyinter ace with a surrounding orest) ace increased risks owing to expected increases inwild re activity in some locations. Third, changes in wood supply or in the relativecompetitiveness o local rms can have signi cant impacts on local economies,particularly in cases in which those economies are heavily dependent on the orest-products sector. Additional socioeconomic actors that contribute to the heightened levelso vulnerability o Canadian orest-based communities include the ollowing:

The potential for lower adaptive capacity (e.g., small and undiversi edeconomies and overspecialized local labor orces with skill sets that are nottrans erable to other sectors),

the potential for larger scale institutional responses to environmental issuesand climate change that are targeted to our increasingly urban society and thatultimately a ect smaller rural communities or reduce their capacity to adapt,

a lack of consideration of climate change in forest management decisions andorestry institutions that may ultimately lead to higher impacts mani esting at

the community level, and the potential for misperception of the risks of climate change.

Forest-based public and common-property goods and services

Climate change will a ect a range o environmental goods and services associated with

orests. These goods and services include clean air and water, productive soils, wildli e,protection and preservation o biodiversity, existence value (i.e., the knowledge thatcertain species or ecosystems continue to exist), bequest value (i.e., the knowledge thatwe are preserving natural capital or uture generations), the provision o aestheticallypleasing vistas, and the provision o outdoor recreation opportunities. For example, thereare concerns about the impacts o climate change on endangered species such aswoodland caribou.

r a a uThe magnitudes o change in climate that will be aced by Canadas orests and orest

sector and the consequent scale o expected impacts have no historical analogue.Canadas orest sector will need to adapt and it will need to do so without the bene t oprior experience. Forest managers can expect the unexpected and they can expect thatchange will be ongoing and unrelenting. Adapting orest management to climate changeis starting to be recognized as a necessity. Adaptation leads to a number o bene ts,including exploiting opportunities and maximizing potential bene ts, reducing potentialnegative impacts, and reducing risks. There are a number o examples in Canadian

orestry that show that the process o adaptation has already begun. A ew companies areinvestigating how to incorporate climate change into their long-term orest managementplanning. A ew provincial orest management agencies are beginning to consider theiradaptation requirements. These are, however, preliminary steps and much more needs to


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be done to prepare or and adapt to uture climate change. Although there is growingrecognition o the need to adapt to climate change, there remains some degree ouncertainty about where and how to adapt. A use ul rst step would be to identi y andbetter understand sources o vulnerability in orest ecosystems and the orestmanagement system.

Even a ter sources o vulnerability have been documented, unexpected impacts willprobably be experienced. Thus, in addition to the development o speci c adaptationmeasures, there is also a need to enhance the general capacity o orest managers and

orest management to adapt. Not only would this be o value with respect to climatechange but also it would position the orest sector to address the ull array o global,social, political, and economic changes that it aces. According to Smit and Pilosova(2001), core attributes o systems with high adaptive capacity include an awareness o andan understanding o the urgency o the issue; a strong science capacity and access totechnological options or adaptation; nancial resources; e ective institutions that are

orward looking, fexible, and sel -adaptive and that provide the authority or localadaptation to occur; high levels o human capital; e ective networks and high levels o

trust between various vested interests to acilitate in ormation sharing and thedevelopment o collaborative solutions; and mechanisms or knowledge generation anddissemination and or the creation o tools and databases.

r a1. Enhance the capacity to undertake integrated a e ent of vulnerabilitie to cli ate

change at variou cale

Integrated assessments o vulnerabilities to climate change are required at multiplespatial and temporal scales and or various types o human systems. For example, an

understanding o system vulnerabilities is required at national, regional, and local scales.Methods and approaches are required that consider the vulnerabilities o di erent typeso human systems to climate change, including orest management systems, protectedareas, and orest-based communities.

2. Increa e re ource for i pact and adaptation cience and al o increa e re ource to onitor the i pact of cli ate change.

Climate change is a reality and it has major implications or the uture state o orests.Foresters rely on prediction models (e.g., growth and yield and timber supply) to manage

orests to achieve social objectives or public orests. In the past, historical data was used

in estimating prediction models. This is no longer valid. Historical conditions are notrepresentative o uture conditions. Decisions made today that are based on expectationsthat uture conditions will match historical conditions will likely ail. Thus, our success atmanaging orests depends on our ability to predict the uture impacts o climate changeon orests. However, the di culty that orest managers ace is that although climatechange produces a greater need to predict the uture (under changing conditions), it alsoproduces greater uncertainty surrounding predictions o the uture. Increased resources

or monitoring the impacts o climate change and or impacts and adaptation research canreduce this uncertainty. More reliable prediction methods, lower uncertainty regardingpredictions, and the ability to provide projections at scales relevant to decision-makers


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will be essential i we are to develop e cient and e ective strategies or adapting toclimate change.

3. Review fore t policie , fore t planning, fore t anage ent approache , and in titution to a e our ability to achieve ocial objective under cli ate change

The Canadian orest sector has been hesitant to incorporate climate change into policyand planning. This may in part be due to the high levels o uncertainty that are associatedwith the uture impacts o climate change, especially at the stand and orest levels.Nevertheless, orest companies are already beginning to experience some impacts thatmay be related to climate change (e.g., a shorter winter-harvest season and the expansiono the mountain pine beetles range). Moreover, the long growth cycles o trees puts orestmanagement in a unique position in terms o the need to include climate changeconsiderations in current planning and decision-making. Thus, consideration o climatechange is not something that should be de erred in the orest sector.

There are a number o areas in which uture climate change has important implications orcurrent orest management. There is a need to:

incorporate climate change into growth and yield forecasts. incorporate climate change into long-term timber supply analysis and forest

management planning. incorporate climate change into reforestation choices. consider climate change in identifying protection program requirements and in

speci c types o adaptations, such as reducing vulnerability by managinglandscape con gurations (e.g., re-smart landscapes, insect-proo edlandscapes).

incorporate climate change considerations into sustainable forest managementobjectives and into the practices that orest managers use or may use to

achieve modi ed objectives.

A cumulative e ects approach may, in some cases, be needed to determine appropriateactions. For example, some areas will be subject to increased risk o both drought and reand there ore a shi t in species composition toward more jack pine could providemultiple bene ts.

4. E bed principle of ri k anage ent and adaptive anage ent into fore t anage ent

Climate change will increase the risk and uncertainty associated with orest managementobjectives. A change in risk may have implications or orest values and or choices made.

It can be argued that the current approach to orest management is prescriptive anddeterministic. A prescriptive and deterministic approach that is based on historicalexperience may be satis actory when conditions are stable but this approach hassomewhat less applicability when conditions could change in multiple possible uturedirections.

Increased timber supply risk resulting rom climate change has the potential to have realeconomic impacts and also to infuence optimal harvest plans. Accounting or andmanaging risk will be an important adaptation to climate change. Risk managementstrategies include risk prevention, risk reduction, risk spreading (e.g., insurance schemes),and port olio diversi cation.


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In addition to the need to manage risk, there is a need to be better prepared to deal withunanticipated and unpredictable events. The mountain pine beetle event, or example,was not anticipated and not predicted. Functional diversity, fexibility, managementsystems that recognize and account or uncertainty and unpredictability, and socialstructures that encourage adaptive management are important eatures in systems thatare vulnerable to unpredicted and unanticipated events.

5. maintain or i prove the capacity for co unication , networking, and infor ationharing with the Canadian public and within the fore t ector

Improving communications, networking, in ormation sharing, collaboration, andcooperation is one way to e ectively address the many challenges aced under achanging climate. Social capital is essentially the degree to which elements o a socialsystem are networked and the degree to which constituents o the social system trusteach other. Social capital provides individuals and groups with in ormation and resourcesto which they might not otherwise have access. It contributes to resiliency and adaptivecapacity.

c uThe purpose o this report is to raise awareness about climate change, its impacts onCanadas orest sector, and its implications or orest management and the orest sector inCanada. Canadas orest sector is experiencing and will continue to experience theimpacts o rapid climate change. This has important implications or Canadas ability tomanage orests in an economically and environmentally sustainable ashion. Ultimately,

orest managers will need to adapt. The in ormation presented in this report should helpto in orm the orest management community and contribute to a more constructivedebate about adaptation requirements.

One strong nding is that we ace signi cant levels o uncertainty regarding the impactso uture climate change. Uncertainty should not be a barrier or prevent adaptation, but itdoes make adaptation somewhat more challenging. Science can help to reduce thisuncertainty over time. Climate change is undamentally a scienti c issue with verysigni cant potential socioeconomic impacts and important policy implications. A stronger,better unded, and more ocused science-based research e ort will be required. However,this scienti c e ort cannot and should not proceed independently o the needs o policy-makers and orest managers. Mechanisms must be put in place to directly link science topolicy, planning, and decision making.


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i n t r o d U c t i o n

c H a p t E r 1

Climate changes naturally over time in response to changes in the earths orbit, changes insolar activity, volcanic activity, and changes in the composition o the atmosphere

(Girardin et al. 2006). Most o these actors, however, result in climate changes occurringover long time periods. The rate o climate change over the last 100 years cannot beexplained by natural actors. According to the Intergovernmental Panel on ClimateChange (IPCC), anthropogenic change in the composition o the atmosphere is the main

actor contributing to recent rapid climate change and will be the principal actor orcingclimate change over the next 100 years (IPCC 2007).

The IPCCs Fourth Assessment Report (IPCC 2007) con rms earlier assessments thatclimate change resulting rom the actions o humans is real and signi cant. The IPCCstates in this report that warming over the last 100 years is unequivocal, with anestimated 0.74 C (0.18 C)increase in mean global temperature during the period 19062005. The report also provides best estimates o projected increases in temperature or the2090s (compared with the period 19801999) ranging rom 1.8 C, assuming the mostoptimistic scenario o uture greenhouse gas emissions, to 4.0 C i emissions were toincrease under the worst-case scenario. For Canada, particularly in the midcontinentalregions, the general circulation models typically project a level o warming that is greaterthan the global average (Kirschbaum and Fishlin 1996; Weber and Flannigan 1997).

Forests are sensitive to climate. Present-day latitudinal and elevation di erences intemperature, precipitation, wind, and radiation explain much o the large-scale spatialvariation in species composition and productivity o orest ecosystems (Iverson andPrasad 1998; Aber et al. 2001; Hansen et al. 2001; Jackson 2004). Climate has a directinfuence on biological and ecological processes. Climate a ects regeneration, phenology,

synchrony in phenology o interacting species, photosynthesis, respiration, water uptakeand transpiration, disturbances (i.e., re, insects, diseases, storms, and drought), thecompetitive success o particular species, and the rates o accumulation anddecomposition o dead organic material. Be ore the onset o signi cant anthropogenicgreenhouse gas emissions, changes in climate were generally slow enough to allowlong-lived tree species to acclimatize, adapt, or migrate. Since then, the climaticenvelopes in which Canadas diverse orest ecosystems developed have begun to shi t atunprecedented rates. The implications o a rapidly warming climate or long-livedorganisms (such as trees) and or human management systems with long planninghorizons (such as orestry) are signi cant (Dale et al. 2000; McNulty and Aber 2001;Chuine et al. 2004).

Concern is growing about the impacts o climate change in the orest sector and the needor adaptation (e.g., see Standing Senate Committee on Agriculture and Forestry 2003;

Lazar 2005; Snetsinger 2006; Lemprire et al. 2008). The Canadian Council o ForestMinisters (CCFM) has identi ed climate-change mitigation and adaptation along withtrans ormation o the orest sector as two priorities o national importance or Canadas

orest sector (CCFM 2008). Canada is in a uniquely vulnerable position relative to othercountries because o the expected magnitude o climate change, the sensitivity o oreststo climate change, the long growing cycles o trees, and the socioeconomic importance toCanadians o orests and the orest sector. Early action, however, has the potential toreduce our vulnerability to climate change. Adaptation may reduce the current negative


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impacts o climate change and may maximize the bene ts rom climate change. Moreover,given that orestry investments mature over long time rames and are generallyirreversible, early adaptation is needed to minimize long-term uture negative impacts oclimate change. There ore, it is important that oresters are aware o climate change andbegin to identi y and incorporate adaptation strategies and approaches in policy,management decisions, and long-term plans.

This report complements and updates previous synthesis documents on the impacts oclimate change on Canadas orests (e.g., Saporta et al. 1998; Forget et al. 2003; Lemmenand Warren 2004; Juday et al. 2005; Johnston et al. 2006; Lemprire et al. 2008). The reportis based on orestry author contributions to the recent Canadian national assessmentreport on climate change impacts (Lemmen et al. 2008). The purpose o the report is toraise awareness about climate change and to provide in ormation to orest managers toassist them in beginning to identi y and assess adaptation requirements and options. Thereport provides a summary o changes and events that have occurred in Canadian orestryover the last 30 years that may be at least partially related to recent climatic trends. It thendescribes how uture climate change might a ect orests and the orest sector both in

general terms and in various regions throughout Canada. The potential implications oclimate change or orest management, orestry operations, the orest industry, and

orest-based communities are considered. Finally, adaptation challenges, considerations,and options are discussed and recommendations are provided.


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Climate change is already a ecting Canadas orests (Lemmen et al. 2008). This chapterdescribes recent changes in Canadian orests that are related in some way to recent

climate change. The most visible e ects o climate change in the Canadian orest sectorover the last 30 years are in the orm o changes in the requency, severity, or geographiclocation o disturbances (see gure 1). However, changes in the length o the growingseason, tree lines, and phenology are also being observed. The examples discussed inthis chapter were chosen because they provide evidence that climate change is having animpact now. Moreover, the kinds o climate change and impacts that are currently beingobserved may be precursors o even more signi cant events in the uture as our climatecontinues to warm at a potentially accelerating rate.

o a a , , a

Climate change is increasing the length o the growing season. Zhou et al. (2001) oundthat the average length o the growing season (expressed as period o vegetationgreenness) increased 12 days in North America and 18 days in northern Eurasia between1981 and 1999. Similarly, McDonald et al. (2004) ound that the mean date o spring thawin North American boreal orest ecosystems advanced by 13 days between 1988 and 2001;Goetz et al. (2005) reported similar patterns in tundra regions o Canada and Alaska.

Trees are starting to respond to climate change. Bernier and Houle (2005) noted that budburst or sugar maples is occurring several days earlier than it did a hundred years agoand Colombo (1998) reported similar results or white spruce in Ontario. Beaubien andFreeland (2000) reported that the fowering period or aspen poplar is now occurring 26

days earlier than it did in the last century. Danby and Hik (2007) ound that tree lines haveexpanded upward in elevation and stand densities have increased in the Yukon as a resulto warming during the 20th century. Roland and Matter (2007) also noted that the tree lineis increasing in elevation. The result is encroachment on alpine ecosystems. Soja et al.(2007) described a similar result or Siberia. Gamache and Payette (2004) reported thatblack spruce trees have been growing taller in the northern oresttundra o easternCanada since 1970.

t 20012003 uA speci c event that may be tied to recent climate change is the nationwide drought in

20012003. Droughts are normal in Canada: or example, signi cant droughts occurred inthe early 1930s, 1961, and 1988 and most recently in 20012003 (Wheaton 2005). However,the 20012003 drought was unprecedented in terms o length, aerial extent, and (in somelocations) severity (Wheaton 2005). This drought was not restricted to Canada. Forexample, Zeng et al. (2005) and Lotsch et al. (2005) described a drought event thatoccurred over mid-latitude regions across the northern hemisphere rom 1998 to 2002.

c U r r E n t i m p a c t s o n c a n a d a s o r E s t s

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Aspen dieback started to be observed in the early 1990s (Hogg et al. 2002). On the basis oaerial surveys conducted in 2004, Hogg et al. (2005) noted that the 20012003 droughtmay have contributed to widespread mortality o aspen trees in western Saskatchewanand eastern Alberta. This was con rmed in a paper by Hogg et al. (2007) that nds thataspen orests in the western Canadian interior orests are moisture limited and that therecent drought contributed to increased stem mortality and growth decreases in these

orests.

Drought may also have secondary a ects. For example, the devastating re seasons inBritish Columbia and the Yukon in recent years are likely due to a combination oincreased uels (the result o mortality caused by insect in estation) and the hot, dryconditions that are associated with drought. Drought increases tree stress and thesusceptibility o trees to diseases and parasites (Dale et al. 2001). For example, Juday andcolleagues (2005) cited drought as a potential actor contributing to increased mortalitycaused by the spruce bark beetle in the spruce orests o Alaskas southern peninsula.

i a f aFire activity in a speci c region during a particular year is related to the weather in thecurrent and previous years, atmospheric conditions, lightning activity, ocean currents (i.e.,El Nino and La Nina), the availability o uels (i.e., orest vegetation characteristics),decomposition rates (which a ect uel accumulation), land-use activities, topography andterrain eatures, and re management (Flannigan et al. 2001; Podur et al. 2002). These

actors are interrelated and they are in some cases stochastic (e.g., weather). Thus, thelevel o re activity in a particular area can vary widely rom year to year.

One example o how recent climate change is a ecting re activity is that extreme reseasons are occurring more requently and it is becoming more commonplace or severe

burning conditions to occur at times o year when they typically do not occur. Forexample, the 2003 re season in British Columbia was worse than any previous reseason in the provinces history. The total cost o re ghting was estimated at $700million (Filmon 2004). Over 334 homes and businesses were destroyed, and over 45 000

people were orced to evacuate their residences (Filmon2004). Similar abnormal re activity has occurred in otherparts o Canada. The summer o 2004 was the warmest onrecord in the Yukon. The Yukon also experienced belownormal precipitation and a record number o lightning

strikes in that summer. These conditions combined to produce a record re season in theYukon; approximately 1.8 million hectares burned. The previous record (in 1958) was less

than hal this area: 891 000 hectares. Abnormal re weather conditions have also beenobserved in eastern Canada. For example, extreme re weather conditions existed innorthwestern Ontario as late as September 2006. Fire suppression operations are alsobeginning to gear up much earlier in the season than in previous years.

The assessment o trends in orest re activity is complicated by poor data rom the earlypart o the 20th century (i.e., the area burned was probably underestimated be ore 1960[Amiro et al. 2004]) and the highly variable nature o orest re activity rom year to year.Nevertheless, re researchers have established that orest re activity has increasedsigni cantly over the last 40 years (Flannigan and Van Wagner 1991; Podur et al. 2002;Stocks et al. 2002; Gillett et al. 2004; Amiro et al. 2004; Juday et al. 2005; Soja et al. 2007).

extreme fre seasons are occurring more requently


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6

Kasischke and Turetsky (2006) reported that despite concurrent increases in suppressioncapacity, the requency o large re years and the area burned in the North Americanboreal region (i.e., Alaska and Canada) doubled between the 1960s1970s and the1980s1990s. Most o these increases occurred in the western part o the boreal orestregion. In addition, the proportion o the total area burned at the beginning and end othe re season is increasing, suggesting that there has been a general lengthening o thetime period when orests are susceptible to orest re.

Flannigan and Harrington (1988), Gillett et al. (2004), and McCoy and Burn (2005) notedthat although many actors infuence re activity, temperature is one o the strongestpredictors o area burned. Westerling et al. (2006) discussed the linkage between globalwarming and orest re activity in the western United States. They ound that snowpacksare melting 14 weeks earlier then they did 50 years ago, summer temperatures arehigher, the re season has increased by 78 days, and the average burn duration o reshas increased rom 7.5 days to 37.1 days. These changes have resulted in a 4- old increasein the requency o large res and a 6- old increase in area burned in the westernUnited States.

Although there is evidence that climate change has contributed to increased re activityover the last 40 years, there is a need or some quali cation and historical context. First,in addition to varying over time, orest re activity varies by region. In general, the recycle (i.e., average number o years between stand-replacing res) is longer in easternportions o the boreal orest than in western portions (Bergeron et al. 2006). Second,although orest re activity has increased in recent years, re activity in the early part othe 20th century may have been much lower than in the 19th century (Bergeron andFlannigan 1995; Bergeron et al. 2004, 2006; Girardin et al. 2006).

m u a The mountain pine beetle is native to North America. The primary host o the mountainpine beetle is mature lodgepole pine but this pest does attack other species o pine,including Ponderosa pine and jack pine (Cerezke 1995; Carroll et al. 2004). Beetles eed onlive phloem tissue under the bark, eventually killing the tree through girdling. They alsocarry the blue stain ungus. This ungus spreads through a trees sapwood and eventuallystops the movement o water rom the roots to the crown.

The mountain pine beetle is normally an innocuous orest pest. However,outbreaks occasionally occur that result in widespread pine mortality over largeareas. There have been our major outbreaks o mountain pine beetle in BritishColumbia over the last 120 years (Taylor et al. 2006; Carroll 2006). The currentoutbreak is by ar the most widespread. As o 2005 over 8.7 million hectares opine orest in British Columbia were a ected (BC Ministry o Forests and Range2006). This area is 10 times larger than that a ected by any o the previousin estations (Carroll 2006). Moreover, the regions currently being a ected havenever previously been exposed to mountain pine beetle attacks. To date thebeetle has killed about 40% o the provinces inventory o mature lodgepole pine(Walton et al. 2007). Projections suggest that the in estation could result in theloss o 77% o the provinces mature pine by 2014 (Walton et al. 2007). The mountain pinebeetle has recently spread rom British Columbia into regions o northwestern Albertathat have never be ore been in ested. Signi cant populations have become established in


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areas around Grande Cache and Grande Prairie and on the border o Alberta and BritishColumbia west o Peace River.

Two actors have contributed to the current outbreak: the presence o large areas omature lodgepole pine, and an unprecedented number o abnormally warm winters inconsecutive years (Carroll et al. 2004). Previously, the geographic range o the mountain

pine beetle was limited by climate. Recent changes in British Columbias climate haveresulted in a greater than 75% increase in climatically optimal beetle habitat (Carroll et al.2004). The impacts on timber supply and consequently on British Columbias oresteconomy and orest-based communities are signi cant (see Chapter 5 on impacts on the

orest sector).

s u a The Yukon is currently experiencing the largest outbreak o spruce bark beetle everrecorded. Although the beetle is endemic to the area, population levels have traditionallybeen low, the area in ested has been small and impacts have been limited. Historically,

the main actors limiting beetle distribution were cool, wet summers and cold winters.The beetle required two ull years to complete its li e cycle because the summers werecool. Consecutive cold winters generally resulted in beetle mortality and reducedpopulations (Juday et al. 2005; Berg et al. 2006). The scale o the current outbreak isunprecedented. Forests covering over 340 000 hectares in southwest Yukon have beena ected ( accessed 5 March 2007) and therehas been some tree mortality in 1.6 million hectares in Alaska because o this outbreak aswell (Juday et al. 2005). The primary host o the beetle is mature spruce (i.e., Sitka spruce,white spruce, and hybrids). The current outbreak is directly related to the recent droughtand the unprecedented warm summer and winter conditions in the Yukon and Alaska(Berg et al. 2006; Soja et al. 2007). Beetle populations are beginning to decline in Alaska,primarily because o reduced availability o live host trees.

d a The mountain pine beetle in estation, the spruce bark beetle outbreak, and the increase in

orest re activity are three disturbances related to climate change that are occurring overrelatively large spatial scales. Other equally unprecedented impacts o recent climatechange on orests are occurring at smaller scales. Dothistroma needle blight is a ungusthat attacks the oliage o lodgepole pine and other pine species (Woods et al. 2005). The

ungus normally has a minor impact on orests. However, it has recently become anepidemic in northwestern British Columbia, attacking bothyoung lodgepole pine plantations and mature lodgepolepine orests. It is causing extensive mortality in lodgepolepine plantations and some mortality in mature pine (thedamage in mature pine is unprecedented). Woods et al.(2005) conducted aerial surveys rom 2002 to 2004. O the41 000 hectares they surveyed, 92% were in ected. Nine

percent o the area will need to be replanted because o pine plantation ailure, and 7% othe area has trees that have been killed by the needle blight (Woods et al. 2005). Hostavailability and changes in environmental conditions that avor the pathogen are the main

actors contributing to the increase in damage caused by dothistroma needle blight. The

Other equally unprecedented impacts o recent climate change on orests are occurring at smaller scales.


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8

environmental change associated with the outbreak is an increase in the requency owarm rain events during the summer compared with the mid-1990s (Woods et al. 2005);this may be due to recent climate change.

i aThe examples in this chapter show that climate change is already a ecting Canadas

orests and they illustrate two general characteristics o the impacts o climate change.First, events such as the mountain pine beetle in estation are o ten the result o a numbero interacting actors. Changes in local climate may contribute to the event, but manyother actors (e.g., characteristics o speci c disturbance agents, interactions betweendisturbances, tree and orest-ecosystem characteristics, and previous management)may also combine to create a set o circumstances that lead to a particular event orimpact. This underscores the multi aceted nature o the assessment o the impacts oclimate change and the many challenges that we ace in predicting impacts resulting romcomplex interactions. It also illustrates that it is possible to reduce the sensitivity o

orests to climate change by managing the landscape.A second eature o climate change that is illustrated by recent experiences is that it hasthe potential to result in multiple, interacting impacts that occur simultaneously. Changesin drought risk, re risk, risk o insect and disease disturbance, growth and yield, andextreme weather risk will all occur at the same time. This has important implications or

orest management. First, orest managers will need to recognize, understand, and adaptto the cumulative impacts o climate change. Assessment

rameworks and adaptation strategies that arecomprehensive, holistic, and integrated are required. Thereis also the potential that the signi cant complexities o therisks associated with climate change could result in under-or over-estimation o risk by decision-makers (Davidson etal. 2003). Surveys o orest managers in British Columbiaand Ontario ound that orest managers elt that the impacts o climate change on orestecosystems were not well understood by the public or the orest-managementcommunity (Ogden and Innes 2007a; Colombo 2006; Williamson et al. 2005). There is,there ore, a need or education, communication, generation o new databases and toolsthat can be used by and will be use ul to orest managers; these initiatives will improveand enhance our basic scienti c understanding o the impacts o climate change.However, because the results o climate change are multidimensional, the research that isundertaken and the knowledge and tools that are produced by scientists will need to bemultidisciplinary, holistic, and integrated.

Climate change has the potential to result in multiple,interacting impacts that occur

simultaneously.


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The impacts described in the previous chapter illustrate that orests are sensitive to rapidclimate change. An understanding o the current impacts o climate change provides a

basis or understanding how uture climate change may a ect Canadas orests. Canadasclimate will continue to warm into the next century. The IPCC reports best-estimate globaltemperature increases o 1.8 C (in the IPCCs B1 scenario, which is its lowest emissionsscenario) to 4.0 C (in the IPCCs A1F1 scenario, which is a ossil- uel-intensive scenario)by 2100 (IPCC 2007). Warming trends will be signi cantly more pronounced at northernlatitudes (Lemmen et al. 2008). The rate o uture warming experienced by Canadas

orests will be signi cantly higher than what was experienced in the last 100 years inCanada and also signi cantly higher than the rate o increase in global averagetemperature over the next 100 years.

This chapter provides an overview o expected uture impacts o climate change onCanadas orests. However, the inter- and intra-relatedness o the site, disturbance, andphysiological actors that contribute to the nal impacts o climate change and the largenumber o these actors make it di cult to systematically describe impacts in astraight orward and integrated way. Climate change will have primary, secondary, andtertiary e ects on orest ecosystems. The many interactions and eedbacks between thesee ects make the story complex. Nevertheless, it is possible to identi y drivers o changeon orests, interactions between these drivers, and some o the overriding variables thatwill ultimately a ect or determine the scale o impacts on orests (Figure 2). The remaindero this chapter discusses many o the items identi ed in Figure 2: the drivers o change(i.e., the items identi ed in the three boxes on the le t side o Figure 2) and then thepotential impacts on orests (i.e., the items within the box on the right side o Figure 2).

Given what we are already seeing in orests, we can predict that changes in disturbanceregimes will be one o the key ways by which climate change will a ect orests in the

uture. The potential e ects o uture climate change on extreme weather, orest res,insects, and disease will be summarized in this chapter. However, climate change will alsoa ect resources required by trees (i.e., moisture, nutrients, heat units), site conditions,and biological processes in individual organisms. These changes will have implications orgrowth, mortality, and regeneration; they will also put pressure on trees to acclimatize,adapt, or migrate. The ways in which climate change will a ect biological processes,productivity, and the composition and structure o orests will be discussed later in thischapter. Next, orest zones will be identi ed where the actors described in the previouschapters combine in such a way that these zones will be particularly sensitive andvulnerable to climate change. This will be ollowed by a review o the literature on theimpacts o climate change on Canadas boreal orest. The chapter concludes with adescription o sources o uncertainty in predicting uture impacts.

e a a a a aAn increase in risk associated with increases in the requency and intensity o extremeweather and climatic events was identi ed by the IPCC as one o ve key categories oreasons or concern about uture climate change (Smith et al. 2001). (The other ourcategories are risk to unique ecosystems, distribution o impacts, aggregate impacts, and

U t U r E i m p a c t s o n c a n a d a s o r E s t s

c H a p t E r 3


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1

risk rom large-scale discontinuities.) Mastrandea and Schneider (2004) suggested that aslightly higher than 2 C increase in average temperature may result in large increasesin the risk o extreme weather and climate. Under a worst case climatic scenario, a 2 Cincrease in Canadas average temperature is possible as early as 2030 (see Figure SPM.6in IPCC 2007).

It seems probable that a warmer atmosphere (i.e., containing more stored heat energy)will generate increased requencies and intensities o extreme events both in weather(e.g., storms) and climate (e.g., droughts) (Berz 1993; Meehl et al. 2000; Easterling et al.2000; Smit et al. 2000; Smit and Pilosova 2002). Examples o extreme phenomena likelyto increase in a warmer climate include thunderstorms and windstorms, hailstorms,intense precipitation events leading to fooding, tornadoes, hurricanes (and tropicalstorms), abnormally warm winters, and periods o hot, dry weather (leading to extreme

orest re conditions, extended re seasons, heat waves, and droughts lasting months oreven years).

Graumlich (1993) and Parmesan et al. (2000) suggested that extreme weather and climatic

variability (and patterns o disturbance related to extreme weather and climatic variability)a ect growth and species morphology and is a actor explaining stand composition andstructure. Changes in extreme weather, climatic variability, and related disturbancepatterns are likely to a ect terrestrial biota in a number o ways: they may orceorganisms to change their reproduction strategies, they may avor species that are betteradapted to increased climatic variability a

Documents

Global Warming and Canada's Forests: from Impacts to Adaptation