DOI: 10.1126/science.1091015 , 1907 (2003); 302Science et al.Thomas Dietz,The Struggle to Govern the Commons www.sciencemag.org (this information is current as of April 24, 2009 ):The following resources related to this article are available online at http://www.sciencemag.org/cgi/content/full/302/5652/1907version of this article at: including high-resolution figures, can be found in the onlineUpdated information and services, http://www.sciencemag.org/cgi/content/full/302/5652/1907/DC1 can be found at: Supporting Online Materialfound at: can berelated to this articleA list of selected additional articles on the Science Web sites http://www.sciencemag.org/cgi/content/full/302/5652/1907#related-content http://www.sciencemag.org/cgi/content/full/302/5652/1907#otherarticles, 10 of which can be accessed for free: cites 41 articlesThis article 202 article(s) on the ISI Web of Science. cited byThis article has been http://www.sciencemag.org/cgi/content/full/302/5652/1907#otherarticles 22 articles hosted by HighWire Press; see: cited byThis article has been http://www.sciencemag.org/cgi/collection/sociologySociology : subject collectionsThis article appears in the following http://www.sciencemag.org/about/permissions.dtl in whole or in part can be found at: this articlepermission to reproduce of this article or about obtaining reprintsInformation about obtaining registered trademark of AAAS. is aScience2003 by the American Association for the Advancement of Science; all rights reserved. The title CopyrightAmerican Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by theScience on April 24, 2009 www.sciencemag.orgDownloaded fromREVIEWThe Struggle to Govern the CommonsThomas Dietz,1Elinor Ostrom,2Paul C. Stern3*Human institutions—ways of organizing activities—affect the resilience of the environ-ment. Locally evolved institutional arrangements governed by stable communities andbuffered from outside forces have sustained resources successfully for centuries, al-though they often fail when rapid change occurs. Ideal conditions for governance areincreasingly rare. Critical problems, such as transboundary pollution, tropical deforesta-tion, and climate change, are at larger scales and involve nonlocal influences. Promisingstrategies for addressing these problems include dialogue among interested parties,officials, and scientists; complex, redundant, and layered institutions; a mix of institu-tional types; and designs that facilitate experimentation, learning, and change.In 1968, Hardin (1) drew attention to twohuman factors that drive environmentalchange. The first factor is the increasing de-mand for natural resources and environmen-tal services, stemming from growth in humanpopulation and per capita resource consump-tion. The second factor is the way in whichhumans organize themselves to extract re-sources from the environment and eject efflu-ents into it—what social scientists refer to asinstitutional arrangements. Hardin’s work hasbeen highly influential (2) but has long beenaptly criticized as oversimplified (3–6).Hardin’s oversimplification was twofold:He claimed that only two state-established in-stitutional arrangements— centralized govern-ment and private property— could sustain com-mons over the long run, and he presumed thatresource users were trapped in a commons di-lemma, unable to create solutions (7–9). Hemissed the point that many social groups, in-cluding the herders on the commons that pro-vided the metaphor for his analysis, have strug-gled successfully against threats of resourcedegradation by developing and maintainingself-governing institutions (3, 10–13). Althoughthese institutions have not always succeeded,neither have Hardin’s preferred alternatives ofprivate or state ownership.In the absence of effective governanceinstitutions at the appropriate scale, naturalresources and the environment are in perilfrom increasing human population, consump-tion, and deployment of advanced technolo-gies for resource use, all of which havereached unprecedented levels. For example, itis estimated that “the global ocean has lostmore than 90% of large predatory fishes”with an 80% decline typically occurring“within 15 years of industrialized exploita-tion” (14). The threat of massive ecosystemdegradation results from an interplay amongocean ecologies, fishing technologies, andinadequate governance.Inshore fisheries are similarly degradedwhere they are open access or governed bytop-down national regimes, leaving local andregional officials and users with insufficientautonomy and understanding to design effec-tive institutions (15, 16). For example, thedegraded inshore ground fishery in Maine isgoverned by top-down rules based on modelsthat were not credible among users. As aresult, compliance has been relatively lowand there has been strong resistance tostrengthening existing restrictions. This is inmarked contrast to the Maine lobster fishery,which has been governed by formal and in-formal user institutions that have stronglyinfluenced state-level rules that restrict fish-ing. The result has been credible rules withvery high levels of compliance (17–19). Acomparison of the landings of ground fishand lobster since 1980 is shown in Fig. 1. Therules and high levels of compli-ance related to lobster appear tohave prevented the destructionof this fishery but probably arenot responsible for the sharprise in abundance and landingsafter 1986.Resources at larger scaleshave also been successfully pro-tected through appropriate inter-national governance regimes suchas the Montreal Protocol onstratospheric ozone and the Inter-national Commission for the Pro-tection of the Rhine Agreements(20–24). Figure 2 compares thetrajectory of atmospheric concen-trations of ozone-depleting sub-stances (ODS) with that of carbondioxide since 1982. The MontrealProtocol, the centerpiece of theinternational agreements on ozone depletion,was signed in 1987. Before then, ODS concen-trations were increasing faster than those of CO2;the increases slowed by the early 1990s and theconcentration appears to have stabilized in recentyears. The international treaty regime to reducethe anthropogenic impact on stratospheric ozoneis widely considered an example of a successfuleffort to protect the global commons. In contrast,international