How Acid Rain Affects Forests, Crops and Wildlife

10 Pages·1992·0.21 MB·English

by  Ontario Ministry of Environment and Energy

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ENVIRONMENT
ENVIRONNEMENT
Environment
WINTER1992 Environnement HIVER1992
HOW
ACID RAIN LES EFFETS DES PLUIES
AFFECTS FORESTS, ACIDES SUR LES FORETS,
CROPS AND WILDLIFE LES CULTURES,
LA FAUNE ET LA FLORE
INTRODUCTION INTRODUCTION
Symptomsofforestdeclinehavebeenobservedin IIyadenombreusesann^esqu'onobserveun
areasofNorthAmericaformanyyears. Thevisible d^rissementdesfordtsdanscertainesr^ionsde
signsincludediebackoftwigsandbranchesinthe I'Amdriquedu Nord. Lessymptdmesduph^nomdne
treecrown,theproductionofsmallerleavesand comprennentledesstehementdesrameauxdela
prematureautumncolorationinfoliage. Thecun-ent cimedesarbres, ladiminutiondelatailledesfeuilles
declineofmapleandhardwoodinCanadaappearsto etleurdecolorationpr^coce. Led^lindes
bemoresevereandmoreextensivethanthoseofthe peuplementsd'drablesetd'autresfeuillusquenous
past. StudiesconductedinOntarioandQuebec observonskI'heureactuelleaupayssembledtre
indicatethataciddeposKion-andotherairpollutants plusmarqu^etplusr^anduqueparlepassd. Des
transportedoverlongdistances--n»ybe ^udesmensesenOntarioetauQuebecr^v^lent
contributingtoforestdecline. quelesd§p6tsacidesetletransportkgrande
distanced'autrespolluantsatmosphdriques
pourraientcontribuerauddp^rissementdesfordts.
THE ROLEOFTHEFOREST
LEROLEdesF0R£TS
Forestsplayavitalroleinthelifeofourplanet.
Throughphotosynthesis,cartx>ndioxideandwater Lesfordtsjouentunr6levitaldansI'dquilibre
reactwithsunlighttofomnorganicmatterand biologiquedelaplan^e. Ellesconvertissent,kI'aide
generateoxygen. Thisprocessallowsplantstostore delalunr^^resolaire, legazcarboniqueetI'eauen
energyderivedfromthesunandprovidethebasic mati^resorganiquesetenoxyg^ne. Ceprocessus,
cartxjnmaterialswhichbecomeplanttissues. appeiephotosynth^se, leurpermetd'emmagasiner
r^nergietir6edusoleiletleurfoumitlecartx>ne
Plantsproducefoliage,woodytissues, roots,flowers, n^cessaire^lafabricationdetissusv^g^aux.
fruitandseeds. Eventually,allthesetissuesfallto
thesoil. Deadleaves,treelitter,fallenwoodand Lefeuillage,lestissusligneux,lesracines,lesfleurs,
deadrootsprovidethesourcesofenergyand lesfruitsetlesgrainesproduitsparlesv6g6taux
nutrientsforfungi,t>acteria,insects, earthwonnsand finissentparsedecomposerdanslesol. Lesfeuilles,
otheranimals. Thelivingforestprovidesshelter, lesracinesetleboisrTX>rtsfoumissentdnergieet
nestingsitesandfoodformanyanimalspeciesand mati^resnutritivesauxchampignon;,bact^ries,
helpstostorewater. insectes,versdeterreetautresanimaux. Lafor§t
procureunabri,unlieudenidificationetdela
Inaddition,forestssupporttheeconomythroughthe nouniture^ungrandnombred'espdcesanimaleset
lumberindustry, hunting,fishingandrecreational aidedconserverlesreserveseneau.
activities.
THE EFFECTSOFACID RAIN Deplus, lesfor§tsrepr6sententunfacteur
6conomiqueimportant : I'industriedu bois, lachasse,
Sulphurdioxide(SOj), isamajorsourceofacidityin lap§cheetdenombreusesactivit6sr6cr6ativesen
rain. Insufficientconcentrations,sulphurdioxidecan dependent.
betoxictofoliage. Inthepresenceofwater,sulphur
dioxideisconvertedtosulphuricacid. Intheformof LESEFFETSPESPLUIESACIDES
acidrain, sulphuricacidisdepositedonsoiland
affectssoilchemistry. L'anhydridesulfureux (SO^)estI'unedes principales
causesde I'acidificationdespluies. Acertaines
Theothermajoracidiccomponentofacidrainisnitric concentrations, leSO^peutetretoxiquepourle
acidwhichisderivedfrom nitrogenoxides(NOx). feuillage. AucontactdeI'eau, ilsetransformeen
Contrarytotheeffectsofsulphurdioxide, nitrogen acidesulfurique. LorsqueI'acidesulfuriqueretombe
compounds maystimulateplantgrowth. This sousformedepluieacide, ilmodifielacomposition
stimulationmaybebeneficialonashorttermbasis chimiquedessols.
but inthelongterm,theeffectsareharmfuland
nitrogenmaybereleasedtotheaquaticsystem. L'acidenitrique,qui estund6riv6desoxydesd'azote
(NOx), est I'autrecompos6acide important.
Themajorityofterrestrialscientistswouldagreethat Contrairementkl'anhydridesulfureux, lescomposes
theimpactofacidraindoes notdirectlydestroythe azot6speuventstimulerlacroissancedesplantes,
abovegroundpartsoftheplants. Whatacidrain mais ilspeuventavoirdeseffetsn6fastesklong
doesisdisruptthenaturalsoilprocesses. This termesurlesv6g6taux, etI'azote risqued'§treIib6r6
includesleachingofsoil nutrientsandareductionin dans lescoursd'eau.
nutrientstatus (calcium, magnesiumandpotassium),
which leadstodecreases insoilpH. Under Lamajoritydessp6cialistesde I'^tudedessols
conditionsoflowsoilpH (lessthan5.2),thereisan s'entendentpourdirequelespluiesacidesne
increasedavailabilityofaluminum. Aluminum, in d6truisentpasdirectementlapartievisibledes
turn,canbetoxictoplantrootsandsoilorganisms. v6g6taux. Lespluiesacidesbouleversentplutdtles
processusnaturelsdusol. Ellesentrainent,entre
Thisisaslowprocess. autres, lelessivagedes mati^res nutritives
contenuesdanslesol (calcium, magnesiumet
Atfirst, soilsareabletocounterinputsofacidic potassium), cequiapoureffetd'abaisserlepHdu
materials. Eventually, however,thebasicsoil sol. LorsquelepHdusolestbas (moinsde5,2),
chemicalswillbeusedupandtheentirebuffering I'apporten aluminiumaugmente. L'aluminiumpeut
capabilityofthesoilwillbelost. Thesoilaciditywill etretoxiquepourlesracinesetlesorganismesvivant
increaseveryrapidlyandadverselyaffectthe danslesol.
terrestrialecosystem. Duetodifferingsoil
composition indifferentregions,thiswillnotoccur L'acidificationdu solestunprocessuslent. Lesol
geographicallyinauniformmanner. Inaddition,the poss6deeneffetunpouvoirneutralisantquilui
timescaleforthisphenomenoncouldvarywidely permetdecontrerleseffetsdespluiesacides.
fromafewyearstoafewcenturies. Toutefois, avecletemps, lessubstances
neutralisantescontenuesdans lesol s'6puisent;
racidit6du solaugmentealorsrapidementet
endommager6cosyst§meterrestre. Gomptetenu
desdifferencesdans lacompositiondessols, I'effet
despluiesacidesn'estpasuniformed'uneregionk
I'autre. Deplus, ladur6edu processusvarie
grandement :ilpeutprendrequelquesann6esou
quelquessidcles.
SUMMARYOFCLASSIFICATION OF SOMMAIRE DE LACLASSIFICATION DE LA
TERRESTRIAL(SOIL)SENSITIVITYTOACID SENSIBILITY DESSOLSAUX D^PCTSACIDES
DEPOSITION INONTARIO ENONTARIO
Thecapacilyofsoilstotolerateacidicinputshas LatolerancedessolskI'acidificationestd6termin6e
beenclassifiedbasedonsoilchemistry,textureand parleurcompositionchimique, leurtextureetleur
depth. Therelativeareasfalling intoeachsensitivity 6paisseur. Letableauci-dessouspr^sente la
classareshowninthetablebelow. sensibilityrelativedusol en Ontario.
Class Totalarea(ktn^) %ofProvince Sensibility Superficietotale Proportiondu
(km') terrttoire(%)
Highlysensitive 335,000
soilswhichareshallow, sandyand/orhavelimited
poolsofbufferingchemicals. Suchconditionsare
prevalentinthe PrecambrianShieldareasofCanada.
Theareas mostlikelytobeaffectedincludethe
Muskokaand ParrySounddistrictsofOntariowhere
acidrain mayenhancethedeclineofsugarmaple
trees. Areasfurthernorth inOntarioorinQuebec
havesimilarsoilconditions, butbecausetheyare
furtherfromthesourceofpollution,theamountsof
aciddepositedarelowerandtheacidificationprocess
proceedsmoreslowly.
Muchoftherecentseverediebackofsugarmaplesin
Ontariowasassociatedwiththedefoliationbythe
ForestTentCaterpillar, especiallyintheMuskoka/
Haliburtonareas. Experimentshaveshownthat
growthoftheinsectwasgreateronfoliagesubjected
toacidicconditionsandthecaterpillarsmatured
earlier, in recentyears,theGypsy Mothhasbeen
spreadingnorthwardinOntarioandcouWcreatean
additionalproblemfortheforests.
Severediebackofwhitebirchtrees intheshoreline
areaofLakeSuperior,especially intheWawaarea
andatothersitesinOntario, iscurrentlyunder
investigation. Potentialcausesofthediebackmay
haveinvolved acidicprecipitationoracidicmarine
fog. Soils inthisareaarecoarselytexturedand
extremelyacidic. Naturalsuccessionofplant
communitiesandchangesinducedbyclimaticshift
cannotbediscounted.
ECONOMICCONSEQUENCES provenantdulacpourraientetreaI'originedece
OFHARDWOOD DECLINE phenomene. Lessolsdelaregion presententune
texturegrossiereetsonttresacides. IIsepeutaussi
• Associatedwiththeacidrainquestionistherapid quelasuccession naturelledescommunautes
reductioningrowthrateofsugarmapletreessince vegetalesetleschangementsentralnesparles
about 1960. Reducedgrowth ratesaremore variationsclimatiquesaI'echelleplanetairesoienten
evidentinareassubjectedtoatmospheric cause.
contaminants. InsouthwesternOntario, acidrain CONSEQUENCES ECONOMIQUES DU DECLIN
andozoneareco-depositedanditisdifficultto DESPEUPLEMENTS DEFEUILLUS
assesstheirrelativecontributionstothereduced
growthrate.
• Onassocielespluiesacidesaladiminutionrapide
With reducedratesofgrowth, lesstimberwillbe dutauxdecroissancedeserablesasucredepuis
producedforfutureharvests. Salvagecuttingof environ 1960. Lephenomeneestplusmarque
affectedtreesinareaswherediebackis dcoanntsalmeisnarnetgisoantsmqousiphsoenrtiqeuxepso.seLeessauudx-ouestde
encounteredisashorttermsolutionanddisrupts rOntarioetantexposeauxdepotsacidesetaux
timberharvestplans.
depotsd'ozone, ilestdifficiled'evaluerI'impact
• Quebecproducesabout70%oftheworld'smaple rcerloatiisfsdaenccehdaecsunardberecs.esdeuxfacteurssurla
syrupandsome 15,000producersinNorth
Americarelyonthesugarbushforatleastpartof Leralentissementdestauxdecroissancedes
theirincome. arbreslaissepresagerunediminutiondesrecoltes
futuresdeboisd'oeuvre. Lacoupede
• Althoughitisdifficulttoassess, lossofforestcover recuperationdesarbresatteintsestunesolutiona
couldhaveamajorimpactonnon-timberforest courtterme, maiselleperturbelesplans
resourceutilizationsuchashuntingandtourism. d'exploitationforestiere.
RISKSFORAGRICULTURALPRODUCTION • Environ70p. 100delaproduction mondialede
siropd'erableprovientduQuebecetI'erablea
Resultsofexperimentalstudiesindicatethatrepeated Sucreconstitueunesourcederevenuspour
occurrencesofhighlyacidicrainorfogwithapHof quelque 15000producteursenAmeriqueduNord.
lessthan3.0willincreasethelikelihoodoffoliar
damagetoagriculturalcrops. (Rain intheabsenceof • Bienqu'ilsoitdifficiled'enfaireuneevaluation
pollutionisexpectedtohaveapH of5.6, resulting precise, ladiminutiondelacouvertureforestiere
fromdissolvedcarbondioxidewhichisnaturally pourraitavoirun impactmajeursurlesfonctions
presentintheatmosphere.) Directdamagehasnot desforetsautresquelarecoltedeboisd'oeuvre,
beenverifiedundernaturalconditionsasthepHof dontlachasseetletourisme.
typicalrainfallisabout4.2insouthernOntario. IMPACTSSURLAPRODUCTIONAGRICOLE
AcidicdepositioncouldresultinsoilpHdepression.
Thiswouldincreasethefrequencyofapplicationof Lesresultatsd'etudesexperimentalesrevelentque
valgeirmrieycuadliptfpfuliricaucllattltiioomneastwtthroienbneuttneooartnhmyealicnracogrprieclauaslnetddu.rdaIletwmproaauncltddicfeboser, sppllouuusssllfeeossrdpmroeemcdimepaitpgaletuiiseoncosauturdseeessabrcaoiuudxielslcaur(ldptuHsroednsetsmforoneitqnusendtees3,)
importants. (En I'absencedepollution, lapluieaun
includingapplicationofnitrogen-basedfertilizers,will pH de5,6, enraisondugazcarboniquequiest
alsoresultinsoilacidification. presentnaturellementdans I'atmosphere.) Onn'apu
RISKS FORWILDLIFE __^ determinerlesdommagescausesparlespluiesdans
desconditionsnaturelles, carlepHdespluiesdans
lesuddeI'Ontarioestgeneralementde4,2.
• Largescalelossesofthetreecanopyarepredicted
toleadtoadecreasedabundanceofbirdsthatrely Lesdepotsacidespeuventcauserladiminutiondu
onthecanopyforfoodandshelter. pHdessols, cequientra?ne lanecessitedetrailer
plussouventlesterresagricolesavecdelapierrea
chaux. IIseraitcependanttresdifficiled'attribueraux
• Conversely, somebirdspeciesthatfeedamong pierrekchauxsurlesterresagricoles, carles
shrublayersonthegroundmay haveincreased pratiquesagricolesnormales,dontI'application
habitat. d'engraisazot6s,contribuentaussi^I'acidification
dessols.
• Followingsoilacidification, metalsandother
contaminants, especiallycadmium, becomemore INCIDENCESUR LAFAUNE
availableforuptakethrough rootsoftheplantson
whichanimalsfeed. Asaresult,thesemetalscan • Onpr6voitqu'unediminution importanteducouvert
beaccumulatedinthetissuesofwildlifeinremote forestierentraineraund6clindespopulations
areaswhicharesensitivetoacidification. d'oiseaux,carlesarbressontlasourcede
nourritureetI'abridesoiseaux.
• Mareetaalsfoaordeskonuorwcnetfoorawcilcdulmifuel.atMeooinsleicahnednsdweheirchhave • qDueiftraoguovnenrt6ciiepurroqnuoeu,rrcieturrteaidnaensseslepskibeuissds'oonisseoauuxsur
accumulatedsuchhighconcentrationsofcadmium leso!profiteraientd'unhabitatplusvaste.
intheirliversandkidneysthattheseorganshave
beendeclaredunfitforhumanconsumption in • L'acidificationdessolsentrainelamobilisationde
severalprovincesinCanada. m6tauxetd'autrescontaminants, enparticulierle
cadmium. Cessubstancessontabsorb6esparles
FOR MOREINFORMATION racinesdesplantesdontlesanimaux se
nourrissent. Des m6tauxpeuventparconsequent
EnvironmentOntariohasseveral informationpieces s'accumulerdanslestissusdesanimauxvivant
aboutacid rainandothertopics. Theseareavailable dans les r6gions6loign6essensiblesauxeffetsde
throughtheministry's Public Info/'mationCentre, l'acidification.
located at 135St.ClairAve. W., Toronto,Ontario
M4V1P5. ThePublic InformationCentreisopen • Les m6taux s'accumulentaussidansleslichens,
Mondaythrough Friday,from9;00 a.m.to4:30p.m. dontsenourrissent lesanimaux. Les
concentrationsdecadmiumdanslefoieet lesreins
Orcall: desorignauxetdeschevreuiissonttenement
6lev6esquecesorganesont6t6d6clar6s
OutsideofToronto 1-800 565-4923 impropresklaconsommationdansplusieurs
inToronto323-4321 provincescanadiennes.
RENSEIGNEMENTSADDITIONNELS
REFERENCES
EnvironnementOntarioapubli6plusieursdocuments
GeorgeH.Tomlinson "EffectsofAcid Depositionon d'informationsurlespluiesacidesetsurd'autres
theForestsofEuropeandNorthAmerica" 1990. sujets. Vouspouvezvous lesprocurerau Centre
d'informationdu Minist6re,situ6au rez-de-chauss6e
The1990CanadianLong-RangeTransportofAir du 135,avenueSt. Clairouest,Toronto(Ontario)
PollutantsandAcid DepositionAssessmentReport, M4V 1P5. LeCentred'information estouvertdu
Part5,Terrestrial Effects. 1990 iundiauvendredi,de9h^ 16h
Acid PrecipitationinOntarioStudy(APiOS)Annual T6I.: 1-800-565-4923 (deI'ext6rieurdeToronto)
Program Report. 1989/1990. 323-4321 (kToronto)
BIBLIOGRAPHIE
GeorgeH.Tomlinson EffectsofAcidDepositionon
theForestsofEuropeandNorthAmerica, 1990.
Rapportcanadiend'6valuationde 1990surle
o transportAdistancedespolluantsatmosphdriqueset
surlesdepotsacides.partie5. effetssurlesmilieux
terrestres.
RECPYRCIILfElDEPDOANPO
DUMPP«>f1lElRuRCEeCUYRCti^ EtudessurlesprecipitationsacidesenOntario
PIBS1736b (EPAO), rapportannuel1989-1990.
01/92
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