XTENSIONS OF
A
AMERICAN
AsSOCIA,TION
FOR
THE
THEHE
ADVANCEMENTOF
SCIENCE
OF
TRAGEDY
R G D
THE
COMMONS
150 YEARS * 1848-1998
omm
W0
It is easyto call for interdisciplinary
synthewouldnot crystallize.
Repeatedly,I foundfault a:0
ses,butwill anyonerespond?
Scientistsknow
withmy own conclusions.
how to trainthe youngin narrowlyfocused
With AdamSmith'sworkasa model,I had
work;but how do you teachpeopleto stitch
assumedthat the sumof separateego-servingz
togetherestablishedspecialtiesthat perhaps
decisionswouldbe the bestpossibleone forthe a:
shouldnot have been separatedin the first
populationas a whole.ButpresentlyI discov- 0
place?Earlyin this centurythe specialtiesof
ered that I agreedmuch morewith William
biologyand chemistrywere joined to form
ForsterLloyd'sconclusions,asgivenin hisOxbiochemistry;
similarly,
economicsandecolofordlecturesof 1833.Citingwhathappenedto
gy arenow in the processof beingcombined
leftopen to manyherdsof cattle,
pasturelands
into ecologicaleconomics.
Lloydpointedout that,with a resourceavailanalMy firstattemptat interdisciplinary
able to all, the greediestherdsmenwould
ysis led to an essay,"The Tragedyof the
gain-for a while. But mutualruin was just
Commons."Since it firstappearedin Science GARRETT HARDIN is
aroundthe comer. As demandgrew in step
25 yearsago,it hasbeenincludedin antholo- professoremeritusof human
with population (while supply remained
gies on ecology, environmentalism,
health
fixed), a time wouldcome when the herdscare,economics,populationstudies,law,po- ecologyat the Universityof
men,actingas Smithianindividuals,
wouldbe
liticalscience,philosophy,ethics,geography, California,SantaBarbara.He
trappedby their own competitiveimpulses.
psychology,andsociology.It becamerequired is theauthorof a dozenbooks
The unmanaged
commonswouldbe ruinedby
readingfor a generationof students and basedon manyshortpapers,the overgrazing;
competitiveindividualism
would
teachersseekingto meldmultipledisciplines
be helplessto preventthe socialdisaster.
in orderto come up with betterwaysto live bestknownof whichare "The
So mustit alsobe, I realized,with growing
Tragedyof theCommons"and humanpopulationswhen there is a limit to
in balancewith the environment.
I didnot startout intendingto forgean in- "Livingon a Lifeboat."
availableresources.
The directpsychicgainsof
terdisciplinary
link,butratherto presenta reareoffsetbyeconomiclosseschanparenthood
tiringpresident's
addressto the Pacificdivisionof the American neledthroughthe wholepopulation.It wasso in Lloyd'sday;it
Associationforthe Advancementof Science.Buteven aftersix is even moreso today.I rewrotethe essayfor what I thought
revisions,eachquitedifferentfromthe one before,mysumma- wouldbe the lasttime.
ryof an ecologist'sview of the humanoverpopulation
problem
But in a final reading to my family and friends at a
3,
I_
Zm)
z=M
zn
0o
"Freedom in a Commons
Brings Ruin to All"
The essence of Hardin'soriginalessay.
Picturea pastureopento all.Itis expectedthateach
herdsmanwilltryto keepas manycattleas possible
on [this]commons....Whatis the utility..
.of adding
one moreanimal?....Sincethe herdsmanreceives
allthe proceedsfromthe sale of the additional
animal,the positiveutility[to the herdsman]is nearly
+1....Since, however,the effectsof overgrazing
are
sharedby all the herdsmen,the negativeutilityfor
any particular
decision-making
herdsmanis onlya
fractionof -1. Addingtogetherthe...partialutilities,
the rationalherdsmanconcludes that the only
sensiblecourseforhimto pursueis to add another
animalto [the]herd.And another;and another....
Thereinis the tragedy.Each man is locked into
a system that [causes] himto increasehis herd
withoutlimit-ina worldthat is limited....Freedom
ina commonsbringsruinto all.
-G. Hardin,
"TheTragedyof the Commons"
Science 162, 1243 (1968), p. 1244
SCIENCE * VOL. 280 * 1 MAY 1998 * www.sciencemag.org
stopoveron our way to the meetingin Utah, I was encouragedto modifyit again.I scribbledin the changes,mostnotably the suggestionthat the way to avoid disasterin our
globalworldis througha frankpolicy of "mutualcoercion,
mutuallyagreedupon."Under conditionsof scarcity,egocenteredimpulsesnaturallyimposecosts on the group,and
hence on all its members.
A crudeexamplemakesthe point:I mightliketo robbanks,
but I am unwillingto allowothercitizensto do so. So mostof
us, actingtogether,passlawsthat infringeon the individual's
freedomto robbanks.Foran examplecloserto home,thinkof
0
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domof the seas,butthe freedomof the atmosphere,
whichacts
asa commonsinkforaerialgarbage.
Yetto comearemanyother restrictions
as the world'spopulationcontinuesto grow.
The realitythat underliesall the necessarycurtailmentsis
alwaysthe same-populationgrowth.Yetthe slightestattempt
to limit this freedomis promptlydenouncedwith cries of
Elitism!Big-Brotherism!
Despotism!Fascism!andthe like.We
areslowto mendourwaysbecauseethicistsandphilosophers
of the pastgenerallydid not see that numbersmatter.In the
languageof 20th-centurycommentators,
traditionalthinking
wasmagnificently
verbalanddeplorably
nonnumerate.
what is haDDeningto the freedom to
One of today'scardinaltasks is to
make withdrawalsfrom the oceanic
marrythe philosopher'sliterateethics
"INDIVIDUALISM IS
bankof fishes.In 1625,the Dutchscholwith the scientist'scommitmentto nuarHugoGrotiussaid,"Theextentof the
merateanalysis.Wordsare important,
oceanis in factso greatthatit sufficesfor CHERISHED BECAUSE IT but they often requirea numeratecast.
any possibleuse on the partof all peoWhat I have realizedfromreadingnuPRODUCES FREEDOM,
ples for drawingwater,for fishing,for
merouscriticismsof the theoryof the
BUT THE GIFT IS
sailing."Now the once unlimitedrecommonsis that both LloydandI were
sourcesof marinefishes have become
analyzinga subsetof commons-those
CONDITIONAL: THE
scarceand nationsare comingto limit
where"helpyourself"
or "feelfree"attithe freedomof theirfishersin the com- MORE THE POPULATION tudesprevail.This wasthe messageEumons.Fromhereonward,completefreeropean pioneers in North America
dom leads to tragedy.(And still the EXCEEDS THE CARRYING thoughttheyhadbeengivenbythe land
shibboleth,"thefreedomof the seas,"inthey chose to perceive as unpeopled.
CAPACITY OF THE
terfereswithrationaljudgment.)
Even today, laws encouragingprivate
ENVIRONMENT, THE
My addresswasa success,andthe esaccessto publiclandsformining,pastursaywasprinted6 monthslater,trimmed
ing, and forestryperpetuatesubsidies
MORE FREEDOMS
byhalfand,presumably,
moreappealing
thatsupportmalfunctioning
commons.
in its brevityto a wideraudience.The
Numeracydemandsthatwe takeacMUST BE GIVEN UP.'r
600 reprintswereexhaustedin a matter
countof the exponentialgrowthof livof weeks.
ing systems,while acknowledgingthat
Its message is, I think, still true today. Individualismis cherresources,
whenthoroughly
understood,
willproveto be definishedbecauseit producesfreedom,but the gift is conditional: ableby numbersthat arerelativelyconstant.Of course,under
The morethe populationexceedsthe carryingcapacityof the the impactof newscience,the apparentlimitsof resources
may
environment,the morefreedomsmustbe given up. As cities be pushedbackfor a while;but finallywhat E. T. Whittaker
grow,the freedomto parkis restrictedby the numberof park- called"impotenceprinciples"*-forexample,the lawsof thering metersor fee-charging
garages.Trafficis rigidlycontrolled. modynamics-willexerttheirinfluenceon policy.
On the globalscale,nationsareabandoning
not only the freeTo judgefromthe criticalliterature,
the weightiestmistake
in mysynthesizing
paperwasthe omissionof the modifyingadIn correctingthisomission,one cangenM jective"unmanaged."
a.
conclusionin thisway:"A 'managedcomcn~ eralizethe practical
mons'describeseithersocialismor the privatismof freeenterprise.
Eitherone maywork;eitherone mayfail:'Thedevilis in
sz
II
a:i the details.'Butwith an unmanaged
commons,youcan forget
aboutthe devil:As overuseof resourcesreducescarryingca5
X pacity,ruin is inevitable."With this modificationfirmlyin
of the Commons"is well tailoredforfurtLz place,"TheTragedy
x
therinterdisciplinary
syntheses.
A finalwordaboutinterdisciplinary
work-do not underestimateits difficulties.The morespecialtieswe tryto stitchtogether,the greaterare our opportunities
to makemistakesand the morenumerousare our willingcritics.Science has
been definedas a self-correcting
system.In this struggle,our
primary
shouldbe "thenatureof things."As a matter
adversary
of policy,we mustnot replyin kindto thosecriticswholove to
indulgein name-calling.(Theyareall too numerousin interButcriticswho, ignoringpersonalidisciplinary
undertakings.)
ties, focus on the underlyingnatureof things are the true
friendsof science.
LU
tr
tL
a.
I
The author is professor emeritus of human ecology at the University of
California, Santa Barbara, 399 Arboleda Road, Santa Barbara, CA 93110,
USA. E-mail: [email protected]
*E. T. Whittaker, From Euclid to Eddington (Dover, New York, 1958), p. 59.
www.sciencemag.org * SCIENCE* VOL.280 * 1 MAY1998