Microeconomia

Revisiting the Commons: Local Lessons, Global Challenges Elinor Ostrom, et al. Science 284, 278 (1999); DOI: 10.1126/science.284.5412.278 The following resources related to this article are available online at www.sciencemag.org (this information is current as of October 15, 2009 ):
Updated information and services, including high-resolution figures, can be found in the online version of thisarticle at: http://www.sciencemag.org/cgi/content/full/284/5412/278 This article cites 27 articles, 7 of which can be accessed for free: http://www.sciencemag.org/cgi/content/full/284/5412/278#otherarticles This article has been cited by 151 article(s) on the ISI Web of Science. This article has been cited by 17 articles hosted by HighWire Press; see:http://www.sciencemag.org/cgi/content/full/284/5412/278#otherarticles This article appears in the following subject collections: Ecology http://www.sciencemag.org/cgi/collection/ecology Information about obtaining reprints of this article or about obtaining permission to reproduce this article in whole or in part can be found at: http://www.sciencemag.org/about/permissions.dtl

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REVIEW:SUSTAINABILITY

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Revisiting the Commons: Local Lessons, Global Challenges
Elinor Ostrom,1 Joanna Burger,2 Christopher B. Field,3 Richard B. Norgaard,4 David Policansky5 large groups living within a single country, which involve nested institutions at varying scales. These resources continue to be important as sources of sustained biodiversity and human well-being. Some of the most difficultfuture problems, however, will involve resources that are difficult to manage at the scale of a village, a large watershed, or even a single country. Some of these resources— for example, fresh water in an international basin or large marine ecosystems— become effectively depletable only in an international context (10). Management of these resources depends on the cooperation of appropriateinternational institutions and national, regional, and local institutions. Resources that are intrinsically difficult to measure or that require measurement with advanced technology, such as stocks of ocean fishes or petroleum reserves, are difficult to manage no matter what the scale of the resource. Others, for example global climate, are largely selfhealing in response to a broad range of humanactions, until these actions exceed some threshold (11). Although the number and importance of commons problems at local or regional scales will not decrease, the need for effective approaches to commons problems that are global in scale will certainly increase. Here, we examine this need in the context of an analysis of the nature of common-pool resources and the history of successful andunsuccessful institutions for ensuring fair access and sustained availability to them. Some experience from smaller systems transfers directly to global systems, but global commons introduce a range of new issues, due largely to extreme size and complexity (12). In a seminal paper, Garrett Hardin argued in 1968 that users of a commons are caught in an inevitable process that leads to the destruction of theresources on which they depend. This article discusses new insights about such problems and the conditions most likely to favor sustainable uses of common-pool resources. Some of the most difficult challenges concern the management of large-scale resources that depend on international cooperation, such as fresh water in international basins or large marine ecosystems. Institutional diversity may...