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The notorious `tragedy of the commons' is incorrectly held to be the eventual fate of all resources that are used collectively rather than by individual private owners. This essay reviews several examples around the world of successful collective management of environmental resources - institutional regimes that have operated for decades or even centuries without resulting in degradation of resources. It then explores the features shared by these historically unconnected institutional regimes in order to begin specifying the characteristics of regimes that circumvent tragedy. Successful systems usually have well defined communities of eligible user-managers and clear, easily enforced and environmentally cautious rules to constrain resource use. But they vary greatly in terms of the allocation of the harvested supply of the resource, from hierarchical systems of rights with unequal allocation of the resource to very egalitarian systems that assign equal shares by lottery.

An important proportion of the world's biodiversity is found on oceanic islands. Island endemics frequently have small populations and are known to be sensitive to habitat and community changes, making them prone to extinction. In this paper, we assess the habitat distribution of the terrestrial birds of Pemba, an oceanic island that has been classi®ed has an``Endemic Bird Area''. Most of Pemba has been profoundly altered by human activities and only small patches of natural vegetation remain. However, we found that the six endemic birds (four species and two sub-species) have colonised several of the man-made habitats, including clove plantations and farmland, and remain widespread. Species richness was not reduced in these heavily managed areas when compared to the remnants of tropical forest. Nonetheless, the main strongholds of some endemic species are in habitats which have substantially declined in recent years, and which are likely to be further reduced in area in the medium and long term. For these endemics, particularly the Pemba scops owl (Otus pembaensis), the conversion of areas that were formerly clove plantations to open farmland should be considered a serious threat. #

The editorial discusses the status and prospects of the commons of developed industrialized countries, based on the literature. For the traditional commons, one key variable for long-term development prospects of the commons is found in the way ownership to the commons is structured. A second key variable is the way increasing knowledge, including scientific environmental knowledge, has affected our perception of what a resource is within a commons and its value. The way these two variables characterizing commons: "structure of ownership" and "knowledge of valuable resources" are related is illustrated in a process referred to as "the withering away" with potential for widely diverging outcomes. Also new emerging urban commons are commented on and a more indepth study of both traditional and new urban commons is called for.

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