Vers une vision intgre de la protection de lair et du climat en - - PowerPoint PPT Presentation

SLIDE 1

UCL

Thierry Hance

Vers une vision intégrée de la protection de l’air et du climat en Wallonie : Introduction

SLIDE 2

A safe operating space for humanity

ma mma lsitis0.2–0.5e xtinctionspe rmillion s pe cie spe rye a r16.T

• da

y ,thera teofe xtinction

• fs

pe cie sise s tima te dtobe100to1,000time s

morethan what couldbeconsiderednatural.

Aswithclima techa ng e ,huma na ctivitie sa re thema inca us eof thea cce le ra tion.C ha ng e s inla ndus ee xe rt themos t s ignifica nt e ffe ct. The s echa ng e sincludetheconve rs ionofna tu- ra l e cos ys te msintoa gricultureor intourba n a re a s ;cha ng e sinfre que ncy ,dura tionorma g- nitudeofwildfire sa nds imila r dis turba nce s ; a ndtheintroductionofne ws pe cie sintola nd

andfreshwater environments

17.Thespeedof

clima techa ng ewillbe comeamoreimporta nt drive r ofcha ng einbiodive rs itythisce ntury , le a dingtoa na cce le ra tingra teofs pe cie slos s

18.

Upto30%of a ll ma mma l,birda nda mphib- ia ns pe cie swillbethre a te ne dwithe xtinction

thiscentury19.

Biodive rs ity los soccursa t thelocal to

regional level,but it canhavepervasiveeffects

• nhowtheE

a rths ys te mfunctions ,a nditinte r- a ctswiths e ve ra l othe r pla ne ta rybounda rie s . F

• re

xa m ple ,los sofbiodive rs ityca nincre a s e thevulne ra bilityofte rre s tria la nda qua tice co- s ys te mstoc ha ng e sinclima tea ndoce a na cidity , thusre ducingthes a febounda ryle ve lsofthe s e proce s s e s .The reisg rowingunde rs ta ndingof theimporta nceof functiona l biodive rs ityin pre ve ntinge cos ys te msfromtippingintounde

• s

ire ds ta te swhe nthe ya redis turbe d20.This me a nstha ta ppa re ntre dunda ncyisre quire dto ma inta ina ne cos ys te m ’sre s ilie nce .E cos ys te ms tha tde pe ndonafe wors ing les pe cie sforcriti- ca l functionsa revulne ra bletodis turba nce s ,

suchasdisease,andat agreater risk of tipping intoundesiredstates

8,21.

F roma n E a rth-s ys te mpe rs pe ctive , s e t- tingabounda ryfor biodive rs ityisdifficult. Althoughit isnowa cce pte dtha t arichmix

• fs

pe cie sunde rpinsthere s ilie nceofe cos ys

• te

ms

20,21,littleisknownqua

ntita tive lya bout howmucha ndwha t kindsof biodive rs ity ca nbelos t be forethisre s ilie nceise rode d

22.

Thisispa rticula rlytruea t thes ca leof E a rth a sawhole ,or for ma jor s ubs ys te mss ucha s theBorne

• ra

infore s tsortheAma zonB a s in. Ide a lly ,apla ne ta rybounda rys houldca pture

theroleof biodiversityin regulatingtheresil-

ie nceof s ys te msonE a rth.Be ca us es cie nce ca nnot ye t provides uchinforma tiona t a n a ggre ga tele ve l,wepropos ee xtinctionra te a sa na lte rna tive(but we a ke r)indica tor.Asa re s ult,our s ug g e s te dpla ne ta rybounda ryfor biodive rs ityofte ntime stheba ckg roundra te s

• f e

xtinctionisonlyave rypre limina rye s ti- ma te .Morere s e a rchisre quire dtopindown thisbounda rywithg re a te rce rta inty .Howe ve r, weca ns a ywiths

• meconfide

ncetha t E a rth ca nnots us ta inthecurre ntra teoflos swithout

significant erosion of ecosystem resilience.

Nitrogenandphosphoruscycles Mode rna g ricultureisama jor ca us eof e nvi- ronme nta l pollution,includingla rge

• s

ca le nitrog e n- a ndphos phorus

• induce

de nviron- me nta l cha ng e

23.At thepla

ne ta rys ca le ,the a dditiona l a mountsofnitrog e na ndphos pho- rusa ctiva te dbyhuma nsa renows

• la

rg etha t

theysignificantlyperturbtheglobal cyclesof thesetwoimportant elements

24,25.

Huma nproce s s e s—prima rilythema nu- fa ctureof fe rtilize r for foodproductiona nd thecultiva tionof le guminouscrops—con- ve rt a round120milliontonne sof N2from thea tmos phe repe r ye a r intore a ctiveforms —whichismoretha nthecombine de ffe cts froma llE a rth ’ste rre s tria lproce s s e s .Muchof thisne wre a ctivenitrog e ne ndsupinthee nvi- ronme nt,pollutingwa te rwa ysa ndthecoa s ta l zone ,a ccumula tinginla nds ys te msa nda dd- inganumbe r of ga s e stothea tmos phe re . It s lowlye rode sthere s ilie nceof importa nt E a rths ubs ys te ms .Nitrousoxide ,for e xa m- ple ,isoneof themos t importa nt non-CO

2

gre e nhous ega s e sa ndthusdire ctlyincre a s e s

radiativeforcing.

Anthropoge nicdis tortion of thenitro- g e ncyclea ndphos phorusflowsha ss hifte d thes ta teofla kes ys te msfromcle a r toturbid wa te r26.Ma rinee cos ys te msha vebe e ns ubje ct tos imila r s hifts ,for e xa m ple ,duringpe riods

• f a

noxiaintheBa lticS e aca us e dbye xce s

• s

ivenutrie nts

27.The

s ea ndothe r nutrie nt- ge ne ra te dimpa ctsjus tifytheformula tion

• f apla

ne ta rybounda ryfor nitroge n a nd phos phorusflows ,whichwepropos es hould beke pttog e the r a sonebounda rygive nthe ir clos einte ra ctionswithothe r E a rth-s ys te m

processes.

S e ttingapla ne ta rybounda ryfor huma n modifica tion of thenitroge n cycleisnot

straightforward.Wehavedefinedthebound-

a rybycons ide ringthehuma nfixa tionof N2 fromthea tmos phe rea sag ia nt‘va lve ’tha tcon- trolsama s s iveflowofne wre a ctivenitrog e n intoE a rth.Asafirs tg ue s s ,wes ugg e s ttha tthis va lves houldconta intheflowofne wre a ctive nitrog e nto25%ofitscurre nt va lue ,ora bout 35milliontonne sofnitrog e npe rye a r.G ive n

theimplicationsof tryingtoreachthistarget,

muchmorere s e a rcha nds ynthe s isofinforma

• tionisre

quire dtode te rmineamoreinforme d

boundary.

Unlikenitrog e n,phos phorusisafos s ilmin- e ra l tha ta ccumula te sa sare s ultofg e

• logica

l proce s s e s .It ismine dfromrocka nditsus e s ra ng efromfe rtilize rstotoothpa s te .S

• me20

milliontonne sofphos phorusismine de ve ry ye a r a nd a round 8.5million–9.5million tonne sof it findsitswa yintotheoce a ns

25,28.

Thisise s tima te dtobea pproxima te lye ight

timesthenatural backgroundrateof influx.

R e cordsof E a rthhis torys howtha t la rg e

• scaleocean anoxiceventsoccur when critical

thre s holdsofphos phorusinflowtotheoce a ns a recros s e d.Thispote ntia llye xpla inspa s tma s s e xtinctionsof ma rinelife . Mode llings ug- g e s tstha tas us ta ine dincre a s eofphos phorus flowingintotheoce a nse xce e ding20%ofthe na tura lba ckg roundwe a the ringwa se noughto

inducepast ocean anoxicevents

29.

Our te nta tivemode llinge s tima te ss ugg e s t tha t ifthe reisag re a te r tha nte nfoldincre a s e

in phosphorusflowingintotheoceans(com- pared with pre-industrial levels),then anoxic

• ce

a ne ve ntsbe comemorelike lywithin1 ,000 ye a rs .De s pitethela rg eunce rta intie sinvolve d, thes ta teof curre nt s cie ncea ndthepre s e nt

• bs

e rva tionsofa brupt phos phorus

• induce

d re g iona l a noxice ve ntsindica tetha t nomore tha n11milliontonne sofphos phoruspe rye a r s houldbea llowe dtoflowintotheoce a ns— te ntime sthena tura l ba ckgroundra te .W e e s tima tetha t thisbounda ryle ve l will a llow

humanitytosafelysteer awayfrom therisk of

• ce

a na noxice ve ntsformoretha n1,000ye a rs , a cknowle dgingtha t curre nt le ve lsa lre a dy e xce e dcritica l thre s holdsfor ma nye s tua rie s

andfreshwater systems.

Delicatebalance Although the plane tary boundaries are de s cribe dinte rmsof individua l qua ntitie s a nds e pa ra teproce s s e s ,thebounda rie sa re

tightlycoupled.Wedonot havetheluxuryof concentratingour effortson anyoneof them

inis

• la

tionfromtheothe rs .If onebounda ry istra ns g re s s e d,the nothe rbounda rie sa rea ls

• unde

r s e riousris k.F

• r ins

ta nce ,s ignifica nt la nd-us echa ng e sintheAma zoncouldinflu- e ncewa te r re s

• urce

sa sfa r a wa ya sTibe t30. Theclima te

• cha

ng ebounda ryde pe ndson s ta yingonthes a fes ideofthefre s hwa te r,la nd, a e ros

• l, nitroge

n–phos phorus , oce a n a nd s tra tos phe ricbounda rie s .Tra ns g re s s ingthe nitrog e n–phos phorusbounda ryca ne rodethe re s ilie nceofs

• mema

rinee cos ys te ms ,pote n- tia llyre ducingthe ir ca pa citytoa bs

• rbCO

2

and thusaffectingtheclimateboundary.

Thebounda rie swepropos ere pre s e ntane w a pproa chtode finingbiophys ica l pre condi- tionsfor huma nde ve lopme nt.F

• r thefirs

t time ,wea retryingtoqua ntifythes a felim- itsouts ideofwhichtheE a rths ys te mca nnot continuetofunctioninas ta ble ,Holoce ne

• like

state.

Thea pproa chre s tsonthre ebra nche sofs ci- e ntifice nquiry .Thefirs t a ddre s s e sthes ca le

• f huma

na ctioninre la tiontotheca pa city

• f E

a rthtos us ta in it. Thisisas ignifica nt fe a tureofthee colog ica l e conomicsre s e a rch a g e nda

31,dra

wingonknowle dg eofthee s s e n- tia l roleof thelife

• s

upport prope rtie sof the

474

NATURE|Vol 461 |24 September 2009

FEATURE

472-475 Opinion Planetary Boundaries MH AU.indd 474 18/9/09 11:12:44

Rockström et al.

A

lthough E a rth ha sunde rg

• nema

ny pe riodsof s ignifica nt e nvironme n- ta l cha ng e ,thepla ne t’se nvironme nt ha sbe e nunus ua llys ta blefor thepa s t 1 ,0 ye a rs

1 –3.Thispe

riodof s ta bility—knownto g e

• log

is tsa stheHoloc e ne—ha ss e e nhum a n civiliza tionsa ris e ,de ve lopa ndthrive .S uch s ta bilityma ynowbeunde r thre a t.S inc ethe Indus tria l R e volution,ane we raha sa ris e n, theAnthropoce ne

4,inwhichhuma

na ctions ha vebe c

• methema

indrive r of g loba l e nvi- ronme nta l cha ng e

• 5. Thiscoulds

e ehuma n a ctivitie spus htheE a rths ys te mouts idethe s ta blee nvironme nta l s ta teof theHoloce ne , withcons e que nce stha t a rede trime nta l or

even catastrophicfor largepartsof theworld.

During the Holoce ne , e nvironme ntal c ha ng eoccurre dna tura llya ndE a rth ’sre g u- la toryca pa cityma inta ine dtheconditions tha t e na ble dhuma nde ve lopme nt.R e g ula r te mpe ra ture s , fre s hwa te r a va ila bility a nd

biogeochemical flowsall stayedwithin arela-

tive lyna rrowra ng e .Now ,la rg e lybe ca us eof ara pidlyg rowingre lia nc eonfos s il fue lsa nd indus tria lize dformsof a g riculture ,huma n a ctivitie sha vere a c he dale ve ltha tcouldda m

• a

g ethes ys te m stha tke e pE a rthinthede s ira ble Holoc e nes ta te .There s ult c

• uldbeirre

ve rs

• iblea

nd,ins

• m

ec a s e s ,a brupte nvironm e nta l cha ng e ,le a dingtoas ta tele s sconduciveto huma nde ve lopme nt6.W ithoutpre s s urefrom huma ns ,theHoloce neise xpe cte dtocontinue

for at least several thousandsof years

7.

Planetary boundaries T

• me

e t thecha lle ngeof ma inta iningthe Holoce nes ta te , wepropos eafra me work bas e d on ‘pla ne ta ry bounda rie s ’. The se

Asa feope ra tingspa ceforhum a nity

Identifyingandquantifyingplanetaryboundariesthat must not betransgressedcouldhelpprevent human activitiesfromcausingunacceptableenvironmental change,argueJ

• hanR
• c

ks trÖ m and colleagues.

Figure1| Beyond the boundary. Theinner green shadingrepresentstheproposed safeoperating spacefor nineplanetary systems. Thered wedgesrepresent an estimateof thecurrent position for each variable. Theboundariesin threesystems(rateof biodiversity loss, climatechangeand human interferencewith thenitrogen cycle), havealready been exceeded.

A t m

• s

p h e r i c B i

• d

i v e r s i t y l

• s

s C h a n g e i n l a n d u s e G l

• b

a l P h

• s

p h

• r

u s N i t r

• g

e n ( b i

• g

e

• c

h e m i c a l S t r a t

• s

p h e r i c O c e a n a c i d i fi c a t i

• n

C l i m a t e c h a n g e C h e m i c a l p

• l

l u t i

• n

( n

• t

y e t q u a n t i fi e d ) a e r

• s
• l

l

• a

d i n g ( n

• t

y e t q u a n t i fi e d )

• z
• n

e d e p l e t i

• n

f r e s h w a t e r u s e fl

• w

b

• u

n d a r y ) c y c l e c y c l e

SUMMARY

• New approachproposedfordefiningpreconditionsfor human

development

• Crossingcertain biophysical thresholdscouldhavedisastrous

consequencesfor humanity

• Threeof nineinterlinkedplanetaryboundarieshavealreadybeen
• verstepped

bounda rie sde finethes a feope ra tings pa ce for huma nitywithre s pe ct totheE a rths ys te m a nd a rea s s

• cia

te d with thepla ne t’sbio- phys ic a l s ubs ys te msor proce s s e s .Althoug h E a rth ’sc

• m

ple xs ys te m ss

• me

time sre s pond s moothlytoc ha ng ingpre s s ure s ,it s e e m stha t thiswill provetobethee xc e ptionra the r tha n therule .Ma nys ubs ys te msof E a rthre a ct in anonline a r,ofte na brupt,wa y ,a nda repa r- ticula rlys e ns itivea roundthre s holdle ve lsof c e rta inke yva ria ble s .If the s ethre s holdsa re cros s e d,the nim porta nt s ubs ys te ms ,s ucha sa mons

• ons

ys te m,c

• ulds

hift intoane ws ta te ,

• fte

n with de le te riousor pote ntia lly e ve n

disastrousconsequencesfor humans

8,9.

Mos t of the s ethre s holdsc a nbede fine dby acritica l va luefor oneor morecontrol va ri- a ble s ,s uc ha sca rbondioxidec

• nc

e ntra tion. Nota llproc e s s e sors ubs ys te m sonE a rthha ve we ll-de fine d thre s holds , a lthough huma n a ctionstha t unde rminethere s ilie nc eof s uc h proce s s e sor s ubs ys te ms—for e xa m ple ,la nd a ndwa te rde g ra da tion—ca nincre a s etheris k tha t thre s holdswill a ls

• becros

s e dinothe r

processes,such astheclimatesystem.

W eha vetrie dtoide ntifytheE a rth-s ys te m proce s s e sa nda s s

• c

ia te dthre s holdswhic h,if cros s e d,couldg e ne ra teuna cce pta blee nvi- ronme nta l c ha ng e .W eha vefoundnines uc h proce s s e sfor which webe lie veit isne ce s

• s

a rytode finepla ne ta rybounda rie s :c lima te cha ng e ;ra teof biodive rs itylos s(te rre s tria l a ndma rine );inte rfe re ncewiththenitrog e n a ndphos phoruscycle s ;s tra tos phe ricozone de ple tion;oce a na cidifica tion;g loba l fre s h- wa te r us e ;c ha ng einla ndus e ;che mica l pol- lution;a nda tmos phe rica e ros

• l loa

ding(s e e

Fig.1and Table). In general,planetaryboundariesarevalues

for control va ria ble stha t a ree ithe r a t a‘s a fe ’ dis ta ncefromthre s holds—for proce s s e s withe vide nceof thre s holdbe ha viour —or a t da ng e rousle ve ls—for proce s s e swithout

472

Vol 461 |24 September 2009

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SLIDE 3

e vide nceof thre s holds .De te rminingas a fe dis ta nceinvolve snorma tivejudg e me ntsof hows

• cie

tie schoos etode a l withris k a nd unce rta inty .W eha veta ke nacons e rva tive , ris k-a ve rs ea pproa c htoqua ntifyingourpla n- e ta rybounda rie s ,ta kingintoa ccountthela rg e unce rta intie stha t s urroundthetruepos ition

• f ma

nythre s holds .(Ade ta ile dde s cription

• f thebounda

rie s—a ndthea na lys e sbe hind

them —isgiven in ref.10.)

Huma nityma ys

• onbea

pproa chingthe bounda rie sfor g loba l fre s hwa te r us e ,c ha ng e inla ndus e ,oce a na c idific a tiona ndinte rfe r- e nc ewiththeg loba l phos phorouscycle(s e e

Fig.1).Our analysissuggeststhat threeof the

E a rth-s ys te mproc e s s e s—c lima tec ha ng e ,ra te

• f biodive

rs itylos sa ndinte rfe re nc ew iththe nitrog e ncycle—ha vea lre a dytra ns g re s s e d the ir bounda rie s .F

• r thela

tte r twoof the s e , thec

• ntrolva

ria ble sa rethera teofs pe cie slos s a ndthera tea t whic hN

2isre

move dfromthe a tm

• s

phe rea ndc

• nve

rte dtore a ctivenitrog e n forhuma nus e ,re s pe ctive ly .The s ea rera te sof c ha ng etha t c a nnot c

• ntinuew

ithout s ig nifi- ca ntlye rodingthere s ilie nceofma jorcom po- ne ntsof E a rth-s ys te mfunctioning .He rewe

describethesethreeprocesses.

Climatechange Anthropog e nicc lima tec ha ng eisnowbe yond dis pute , a nd in therun-up to theclima te ne g

• tia

tionsinC

• pe

nha g e nthisDe c e mbe r, theinte rna tiona l dis cus s ionsonta rg e tsfor c lima temitig a tionha veinte ns ifie d.The reis ag ro wingc

• nve

rg e nc etowa rdsa‘2°Cg ua rd- ra il’ a pproa ch,tha t is ,conta iningtheris ein g loba l me a nte m pe ra turetonomoretha n2°C

abovethepre-industrial level.

Our propos e dclima tebounda ryisba s e d

• n twocritical thresholdsthat separatequali-

ta tive lydiffe re nt c lima te

• s

ys te ms ta te s .It ha s twopa ra me te rs :a tmos phe ricc

• nc

e ntra tion

• f ca

rbondioxidea ndra dia tiveforcing(the ra teof e ne rgy cha ng epe r unit a re aof the g lobea sme a s ure da t thetopof thea tmos

• phe

re ).W epropos etha t huma ncha ng e sto a tmos phe ricC O

2 conc

e ntra tions s hould not e xc e e d3 5 0pa rtspe r millionbyvolume ,a nd tha tra dia tiveforc ings houldnote xc e e d1wa tt pe r s qua reme trea bovepre

• indus

tria l le ve ls . T ra ns g re s s ingthe s ebounda rie sw ill inc re a s e theris kofirre ve rs iblec lima tec ha ng e ,s uc ha s thelos sof ma jor ices he e ts ,a cce le ra te ds e a

• le

ve l ris ea nda brupt s hiftsinfore s t a nda g ri- cultura l s ys te ms .C urre nt C O

2 c

• nc

e ntra tion s ta ndsa t3 8 7p.p.m.v .a ndthec ha ng einra dia

• tiveforcingis1.5W m−2 (ref. 11).

The rea rea t le a s t thre ere a s

• nsfor our pro-

pos e dclima tebounda ry . F irs t, curre nt cli- ma temode lsma ys ig nific a ntlyunde re s tima te thes e ve rityof long

• te

rmc lima tec ha ng efor ag ive nconc e ntra tionof g re e nhous eg a s e s

1 2.

Mos t mode ls

11 s

ugg e s t tha t adoublingin a tmos phe ricC O

2 c

• nc

e ntra tio n will le a d to a g loba l te mpe ra tureris eof a bout 3°C(witha proba bleunc e rta intyra ng eof 2 –4 .5°C )onc e thec lima teha sre g a ine de quilib rium.B utthe s e mode lsdonot inc ludelong

• te

rmre inforc ing fe e dba c kproc e s s e stha t furthe r w a rmthec li- ma te ,s uc ha sde c re a s e sinthes urfa c ea re aof ic ec

• ve

rorc ha ng e sinthedis tributionofve g

• e

ta tion.If the s es lowfe e dba c ksa reinc lude d, do ublingC O

2le

ve lsg ive sa ne ve ntua lte m pe ra

• tureincre

a s eof 6°C(withaproba bleunc e r- ta intyra ng eof 4 –8°C ).Thiswouldthre a te n thee c

• log

ica l life

• s

upport s ys te mstha t ha ve de ve lope dinthela teQua te rna rye nviro nme nt, a ndw

• ulds

e ve re lyc ha lle ng ethevia bilityof

contemporaryhuman societies.

Thes e c

• ndc
• ns

ide ra tionisthes ta bilityof thela rg epola r ic es he e ts .P a la e

• c

lima teda ta fromthepa s t 100million ye a rss howtha t C O

2

conc e ntra tions w e re a ma jor fa ctor in the long

• te

rmcoolingofthepa s t5 0millionye a rs . More

• ve

r,thepla ne twa sla rg e lyic e

• fre

euntil CO

2conce

ntra tionsfe ll be low450p.p.m.v . (±1 0p.p.m.v .),s ug g e s tingtha tthe reisacrit- ica l thre s holdbe twe e n3 50a nd55 0p.p.m.v . (re f.1 2 ).Our bounda ryof 3 50p.p.m.v .a ims

toensurethecontinued existenceof thelarge polar icesheets.

Third,wea rebe g inningtos e ee vide nc etha t s

• meof E

a rth ’ss ubs ys te msa rea lre a dymov- ingouts idethe ir s ta bleHoloc e nes ta te .This include sthera pidre tre a t of thes umme r s e a

icein theArcticocean13,theretreat of moun-

ta ing la cie rsa roundtheworld

11,thelos

sof

massfrom theGreenland and West Antarctic

ic es he e ts

1 4 a

nd the a c ce le ra ting ra te s

• f s

e a

• level riseduringthepast 10–15years

15.

Rateof biodiversityloss S pe cie se xtinctionisana tura l proce s s ,a nd would occur without huma n a ctions . How- e ve r,biodive rs itylos sintheAnthropoc e neha s a c ce le ra te dma s s ive ly .S pe cie sa rebe c

• ming

e xtinct a t ara tetha t ha snot be e ns e e ns inc e

thelast global mass-extinction event16.

Thefos s il re cord s howstha t theba ck- g rounde xtinctionra teforma rinelifeis0 .1 –1 e xtinctionspe r millions pe cie spe r ye a r;for

PLANETARY BOUNDARIES

E arth-system process P arameters Proposed boundary Current status Pre-industrial value

Climatechange (i) Atmospheric carbondioxide concentration (partsper million by volume) 350 387 280 (ii) Changein radiativeforcing (watts per metresquared) 1 1 .5 R ateof biodiversity loss E xtinctionrate(number of species per million speciesper year) 1 >1 00 0.1 –1 Nitrogen cycle(part

• f aboundary with the

phosphoruscycle) Amount of N2 removed from theatmospherefor human use (millions of tonnesper year) 35 1 21 Phosphoruscycle(part

• f aboundary with the

nitrogencycle) Quantity of Pflowinginto the

• ceans(millions of tonnesper year)

1 1 8.5–9.5 ~ 1 S tratospheric ozone depletion Concentration of ozone(Dobson unit) 276 283 290 Ocean acidification Global mean saturation state of aragoniteinsurfaceseawater 2.75 2.90 3.44 Global freshwater use Consumptionof freshwater by humans(km3 per year) 4,000 2,600 41 5 Changein land use P ercentageof global land cover converted tocropland 1 5 1 1 .7 Low Atmospheric aerosol loading Overall particulate concentration in theatmosphere,on aregional basis T

• bedetermined

Chemical pollution F

• r example,amount emitted to,
• r concentration of persistent
• rganic pollutants, plastics,

endocrinedisrupters,heavy metals and nuclear wastein,theglobal environment,or theeffectson ecosystem and functioningof E arth system thereof T

• bedetermined

Boundariesfor processesin red havebeencrossed.Datasources:ref.1 0 and supplementary information

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NATUR E|Vol 461 |24 September 2009

FEATURE

472-475 Opinion Planetary Boundaries MH AU.indd 473 18/9/09 11:12:44

SLIDE 4

Sciences, janvier 2015

SLIDE 5

• Fig. 3. The current status of the control variables for seven of the nine

planetary boundaries. Green zone is the safe operating space (below the boundary), yellow represents the zone of uncertainty (increasing risk), and red is the high-risk zone. The planetary boundary itself lies at the inner heavy

• circle. The control variables have been normalized for the zone of uncertainty

(between the two heavy circles); the center of the figure therefore does not represent values of 0 for the control variables. The control variable shown for climate change is atmospheric CO2 concentration. Processes for which global-level boundaries cannot yet be quantified are represented by gray wedges; these are atmospheric aerosol loading, novel entities and the functional role of biosphere integrity. Modified from (1).

SLIDE 6

• Fig. 2. The global distributions and current status of the control

variables for (A) biogeochemical flows – P, (B) biogeochemical flows – N, (C) land-system change, and (D) freshwater use. In each panel, green areas are within the boundary (safe); yellow areas are within the zone of uncertainty (increasing risk); and red areas are beyond the zone of uncertainty (high risk). Gray areas in (A) and (B) are areas where P and N fertilizers are not applied, in (C) are areas not covered by major forest biomes, and in (D) are areas where river flow is very low so that environmental flows are not allocated. See Table 1 for values of the boundaries and their zones of uncertainty, and 33 for more details on methods and results.

SLIDE 7

• Basculement

majeur et irréversible de l’écosystème terre

 Transformation de 43 % de l’écosystème terrestre en écosystème agricole  Fragmentation et dégradation des écosystèmes naturels  Pollution des Océans avec l’apparition de zones mortes

 450 zones mortes représentant 6,6 millions de Km2  Changements climatiques  Pollution de l’air

SLIDE 8

Quelques réflexions:

 Les 9 élements qui posent les limites des conditions de vie sur terre sont étroitement liés et interdépendants

• Climat et biodiversité
• Climat et acidification des océans
• Pollution chimique et biodiversité
• Occupation de l’espace et biodiversité

 Agir sur le climat

• Urgence
• Aura des impacts sur les autres compartiments
• Peut sembler une contrainte économique à court terme
• Mais est indispensable à moyen terme, y compris pour des

raisons économiques  Repenser l’économie

• Économie circulaire
• Produire localement, consommer les productions locales
• Revoir notre consommation d’énergie dans toutes nos activités

SLIDE 9

Merci de votre attention