europe’s forests and forestry in a changing climate part 2 ... · forests belonging to the...

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Europe’sforestsandforestryinachangingclimatePart2:Biodiversity

andhealth

Biodiversity

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MediterraneanforestsBiodiversity

AmongallEuropeanregions,theMediterraneanappearsmostvulnerabletoglobalchange.Multiplepotentialimpactsarerelatedprimarilytoincreasedtemperaturesandreducedprecipitation.Theimpactsincludedwatershortages,increasedriskofforestfires,andnorthwardshiftsinthedistributionoftypicaltreespecies.AmajorconcernisraisedbythehighlyfragmentedconditionsofforeststandsintheMediterraneanzone;thelackof“green”connectionsandcorridorsintheMediterraneanlandscapemaybecomeveryharmfulinthefutureenvironmentifthepresentforestvegetationmayberequiredtomigratetowardsmoresuitableareas.


Portugal:Thereisatendencythatcurrentspeciesaredisplacedbythosewhicharemoretoleranttodrought,fromsouthtonorthandfrominlandtocoastalareas.Ariseintemperaturemayallowspeciessuchascorkoakandpinetoprosperathigheraltitudesexpandingtheirpotentialdistribution.Presently,inmorearidareas(forexampleininlandsouthernregions),theenvironmentallimitsforforestsurvivalmaybeexceeded;vegetationspeciesbetteradaptedtodroughtandhightemperatureswillbefavouredbyclimatechange,leadingtoanincreaseinbiomassproductivityinthenortherncountry(withgreaterincidenceinthecoastalcomparedtoinlandareas).

Montenegro:Theparticularlyvulnerableforestsincludespruceandbeechinthesubalpinebelt,beechandfirforestsbelongingtotheDinaricvegetationzone,andsub-Mediterraneanforestsofoakandhornbeam.InthesouthernandwesternareasofMontenegrofirstandsareparticularlythreatened.Climatechangecouldaffecttheexpansionofsub-Mediterraneandeciduousforests,bothtowardstheinteriorandtowardshigheraltitudes.

MediterraneanforestsBiodiversityExamplesacrossEurope

Italy:Theactualpossibilitiesfortheforestecosystemstoshiftarescarce,becauseclimatechangeratefarexceedstherateofcolonizationofnewareas,andthepotentialcorridorsareoftenobstructedbyhuman-inducedterritorialfragmentation.Hence,aprogressivedisruptionofforestecosystemscanbeexpected.Studiesindicateaprogressivedeclineofmountainhabitatsforhighaltitudeconifers(redfir,larch,Swisspine)infavourofbeech,oakchestnutanddeciduousoaks,whichrepresentsafirstclearsignofbreak-upoftheItalianforestheritage.


Extremeclimateeventshavehadamajorimpactontemperateforestsoverthelastdecade.Thecomplexinteractionsbetweenclimateandforestmanagementindeterminingsusceptibilitytoextremeeventsmakeitdifficulttounequivocallyattributetheseeventstorecentclimatewarming.

TemperateforestsBiodiversity

Therangesofnortherntemperateforestsarepredictedtoextendintotheborealforestrangeinthenorthandupwardonmountains.Thedistributionoftemperatebroadleavedtreespeciesistypicallylimitedbylowwintertemperatures.SincethelatterareprojectedtorisemorerapidlythansummertemperaturesinEuropeandNorthAmerica,temperatebroad-leavedtreespeciesmayprofitandinvadecurrentlyborealareasmorerapidlythanothertemperatespecies.Spruceisrelativelyvulnerabletoclimatechangeduetoitsshallowrootsystem.Europeanbeech,ontheotherhand,willsubstantiallygrowdueitsrelativelygoodadaptabilityandstresstolerance.



TheAlps:Inthelongterm,thecompositionofmanyforestsintheAlpswillchange.Thiswillbethecombinedresultofchangingclimaticconditionsandcase-by-casehumaninterventioninducedbytheimpactsofclimatechange,e.g.,afforestationwithbetteradaptedtreespeciesafterstorm,fire,droughteventsorinsectcalamities.Itisexpectedthattheshareofdeciduoustreeswillincreaseandconiferoustreesdecrease.Droughtresistantspeciesmayexpandrapidlybytheendofthiscentury.Thisconcernsextantspecies,speciesarrivingfromtheneighbouringMediterraneanregion,andalsoexoticsthathaveprogressivelyspreadintheSouthernAlpssincethe1970sdueinparttoincreasingwintertemperatures.Furthermore,broadleaftreesthataresensitivetolatefrostsduringbud-breakwillextendtheirrangeupward.



UK:Temperatedeciduousforestsandtemperate/borealmixedforestswillexpandandtemperateconiferandborealevergreenforestswillreduce.Underahighendscenarioofclimatechange,theareaoftemperateconiferforestisrestrictedtothehighlandsofScotland.

Estonia:NodrasticchangesareexpectedinthespeciescompositionofEstonianforestsoverthenext100-200years.Theintra-speciesgenomediversityprovidesadditionalflexibilitytohandletheresultsofawarmingclimateduringthenextcentury.

Poland:Oakproductionwilleitherremainthesameasnoworwillincrease.Futureproductionofbeechseemsuncertainandmightdecline,whilespruceproductionislikelytoincrease.

Slovakia:TheproportionofNorwaySpruceintotalcompositionofforestsisexpectedtodecreasefromthecurrent27%tolessthanhalfthispercentageduetoclimatechange.

Slovenia:InthesecondhalfofthiscenturyhighertemperaturesfavourgrowthofEuropeanbeech,incontrasttodrought-inducedgrowthreductionsinbothsilverfirandNorwayspruceconifers,especiallyatlowelevations.

Bulgaria:Atlowerelevationsdrought-sensitivespeciessuchasNorwaysprucewillprobablybereplacedbymoredrought-tolerantspeciessuchasScotspineandblackpine,andforestdiversitywilldecrease.

Hungary:Theappearanceofplantspeciesofsoutherncharacter,suchaseasternhornbeam,Turkeyoak,Hungarianoakisexpected.ThemostdisadvantageousclimaticchangesmaybeexperiencedbylowlandconiferousstandsaswealreadycanseeintheblackpineforestsoftheBalatonhills.

TheNetherlands:Sofarnodoomscenariosareforeseen.

Denmark:AmajorityofexistingtreespeciesthatthrivewelltodayareexpectedtopersistinDenmark,exceptforNorwayspruce.

Alps:AdaptationtoforthcomingclimatechangesmightnotrequireashiftintreespeciescompositionintheAlpsofGermanyandAustria.Thegeneticvariabilityofmostcommontreespeciesisprobablylargeenoughtoaccommodatethemeanchangesintemperatureandprecipitation.

ExamplesacrossEurope


Borealforests

Tundra

BorealforestsandtundraBiodiversity

Underawarmerclimate,itisexpectedthatthenorthernrangelimitsofmostnativetreespeciesinEuropewillexpand.Thesouthernboundaryofsomespecieswillshifttonorthspecificallyattheboundaryofsteppeandforestzones.Climateprojectionssuggestadisplacementofclimaticzonessuitableforborealforestsby150-550kmthiscentury.Thisshiftisfasterthantheestimatedpotentialofmanyspeciestomigrate(20-200kmpercentury)orthecapabilityofmanysoilstodevelopanewstructure.Coniferoustreesarelikelytoinvadetundraregionsunderwarmerconditions.By2100,suitableNorwaysprucehabitatswillberestrictedtothehigherelevationsincentralEuropeandtoareasinnorthernSweden,FinlandandNorway.Broadleavessuchasoakandbeechareexpectedtoshiftfromtoday'srangesinwesternEurope(France,Netherlands,Germany)andthelowerelevationsincentralandeasternEuropetocentral,northernandnorth-easternEurope.

Foresttype:


Norway:ThegeneticvariationinNorwegianforestsislarge,sothebasisfornaturalselectionshouldbefairlygood.SpeciesrequiringwarmsummerswillexpandattheexpenseofNorwayspruce,whileScotspine,usuallygrowingonshallowandnutrientpoorsoils,willbemorecompetitiveandstaymorestable.Themountainforestswillrespondgreatlyresultinginimprovedgrowthandreproduction.

BorealforestsandtundraBiodiversity

Finland:60-80%oftheforestsinsouthernFinlandmayconsistofbirchbytheyear2100.Norwaysprucewilldeclineinthesouth,butincreaseinthenorth.ThewarmingmayalsodecreasetheamountofScotspineinsouthernFinland.

Borealforests

Tundra


Foresttype:

Health


TemperateforestsHealthofforestecosystems

Theimpactofthesummerof2003toGermanforests:Intheyear2004,72%ofalltreesexhibiteddistinctcrowntransparencyorwereratedas“instageofalert”.Thiswasthehighestlevelofrecordeddamagesincethebeginningofforestdamageinventories.Forthefirsttime,themainreasonforthishighlevelofdamageisnotthoughttobepollution,buttheweatherconditionsinthehotanddry“recordsummer”of2003,anditsside-andafter-effects.Theseare•  directdamagethroughdroughtandradiation;•  damagethroughincreasedozonecontentoftheair,asa

consequenceofintensivesolarradiation;•  thespreadofcalamitiesasaconsequenceofthemildwinterin

2003;•  priordamagesthroughdirectweatherimpacts.

DroughtstressTheheatwaveinthesummerof2003showshowstronglyyieldpotentialcanbethreatenedbydroughtstress.Droughtandhightemperaturesledtoaneartotaldepletionofthewaterreservesinforestsoilsavailabletoplants.

LongtermeffectsDamagesthroughextremeweatherconditionssuchasintheyear2003cancontinuetohaveaneffectovermorethan10years,andcanleadtochangesingrowthtrendsinthelongterm,beyondactualreducedgrowthrates.In2003,theconnectionbetweendrought,heatandriskofpestinfestationbecamealsoapparent.Anexplosivepropagationofpests,particularlybarkbeetlesandnunmoths,wasaconsequenceofhightemperaturesanddecreasedvitalityofforestsin2003.



Alps–Airpollution:Duringthelastfewdecadesdifferentairpollutants(especiallyozone)haveleadtosignificantdamagetothemountainforests.TheaveragedamageratefortheentireAustrianforestareaamountsto33%withapproximately7%ofthetreesdamagedmoreseriously.Alps– Droughts:LargenumbersofScotspinearedyinginthedryinner-alpinevalleysoftheEuropeanAlps;inSwitzerland,locallyalmosthalftheScotspinepopulationhasdiedsince1995.Switzerland’stemperaturehasincreasedatmorethantwicetheglobalaverageinthe20thcenturyandmostofthisincreasehasoccurredduringthelast20years.Itwasshownthatthestrongclimaticwarmingthathasoccurredinrecentyearsmaywellbetheindirectcauseofthemortalityobservedintheseforests.Whereassingledroughtyearshadanegativeimpactontreegrowthwithasubsequentfastrecovery,multipledroughtyearsresultedinlong-lastinggrowthdepressions,laggedrecovery,andincreasedriskoftreedeath.Alps– Pestsanddiseases:ScotspinemortalityinValaisresultedfromthecombinedeffectsofdrought,pests,anddiseases.Likewise,theon-goingsprucedeclineinlow-elevationSwissforestswastriggeredbystormsandsubsequentbarkbeetleinfestationsandaggravatedbydrysummers.Alps– Forestsfires:Alsoforestfiresareaffectedbydrought.InregionslikethedryvalleysofthecantonofValais,thedrought-induceddiebackofpinesenhancestheamountofdeadwoodinforestsandthereforetheriskforforestfires.



WindthrowForeststandsdamagedbywindareespeciallyimportantprecursorstooutbreaksastheyquicklyprovidelargequantitiesofoptimalbreedingmaterial.Thusaprojectedincreaseinthewindstormfrequencycouldalsoescalatethebarkbeetlethreattoforestsinthefuture.

PestsClimatechangecouldchangethebehaviourofrelativelyunimportantpests,whichcancauselargedamagesinthefuture.Evensmalloscillationsintemperaturemighthaveextensiveimpactsonforests.Besidesthechangesindistributionsitesofpests,climatechangealsoinfluencesthenumberofrealizedgenerationswithinoneyear.Ifwarmingprolongsvegetationperiod,thenumberofgenerationsofseveralspeciesisexpectedtobehighertothenorthandinhigheraltitudes.

DroughtstressParticularlyinCentralEurope,anincreasedwaterscarcityinteractingwithclimate-sensitivepestdynamicshasbeenrecognizedasthemostsignificantclimatechange-relatedthreattoforests.Theoccurrenceofbarkbeetlesinfirandspruceforestsismostindicativeafterdryperiodswhenphysiologicallyweakenedtreesbecomeeasilyaccessibletobarkbeetlesassecondarypests.

HeatstressSprucebarkbeetleisthemostimportantforestinsectpestinEuropewhosedevelopmentisstrictlyregulatedbyairtemperature.Morefrequentheatwavesincreasethesprucesusceptibilitytobarkbeetleattacks.



Croatia:AirpollutionisoneofthestressfactorsleadingtothereducedvitalityanddryingofforestsinCroatia.Adirectcorrelationbetweenclimatechangesandtheappearanceofplantdiseasesandpestsonforesttreesintheperiod1996-2004hasbeenobservedinCroatia.

Moldova:Bytheendofthiscenturyclimatearidizationinespeciallythenorthernpartofthecountrymayentailparticularlyseriousdryingeffectswithpossiblegradualdisappearanceofforests.Inthenorthernparttheforestswilldryoutintenselyduringthiscentury.Itisquitelikelythatcurrentspeciesofforesttreesmaycompletelydisappear.

Romania:ThemainimpactsonRomanianforestsareanincreaseofaridityofthesouthernandplainareas,andofthehillareas;forestmigrationtohigheraltitudes;forestproductivitydecreaseafter2040,duetotemperatureincreaseprecipitationdecrease;morefrequentinsectattacks.

Belarus:•  Ananthropogenicincreaseofnear-surfaceozoneconcentration

alonewasresponsiblefora15%reductionofbiomassgrowthofdeciduoustreesinthefirsthalfofthe1990sinsomecountriesofWesternandCentralEurope.ForBelarusthisreductionisestimatedat7-9%.

•  Overwinteringconditionsforforestvegetationwillworsenduetoalackorshorterperiodofsnowcover.

•  Certainsignsofgrowingmassbreedingspotsofforestpestsandanumberofinsectspeciesthatdoconsiderableharmtotreestandshavealreadybeenrecordedinthelastdecadeofthelastcenturyandearlythiscentury.

Slovakia:Increaseofdroughtandinsectdamageshaveoccurredoverthelastyears.Luxembourg:Therather“old”forestof

Luxembourghasdegradedamongotherfactorsduetoclimatechange.TheageingoftheforestalsoincreasestheriskofoutbreakofdiseasesandofinfestationbyinsectsandotherparasitesthatcouldproliferateifmoremildwintersandoverallgeneraltemperaturesarerecordedinLuxembourg.

Belgium:Beechstandshaverecentlybeeninvadedbytimber-boringinsects,theimpactofwhichwasthedestructionofmorethan10%ofstandingvolume.



BorealforestsandtundraHealthofforestecosystems

FortheforestsinnorthernEurope,thecombinationofraisedmeantemperatureandahigherfrequencyofextremeeventswillhavenegativeeffectsthatcouldultimatelybeofgreaterimportancethanthepositiveoutcomesofawarmerclimate.Theborealforests,forexample,maybeseverelyaffectedbysummerdryspellsanddroughts,makingtreesmoresusceptibletofrostdamage,windthrow,stormsandattacksbypestsanddiseases.Insectpestswillbenefitfromincreasedtemperaturesandthelongergrowingseason.Thismayincreasethenumberofinsectgenerationseachyear.AnincreaseinminimumtemperaturesinthewintercouldfacilitatethespreadofpestspeciesinScandinaviafromsouthtonorth.

Borealforests

Tundra

Foresttype:

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