that are directly affected by the local actions of individuals and organizations. Local actions are shaped by local, regional, national, and global institutions. The challenge is to design institutional forms capable of accommodating the demands of governance at all the relevant levels while sustaining resources.
The challenge of linkage, as Young (Chapter 8) and Berkes (Chapter 9) both point out, is not to identify an appropriate institutional level for resource management—institutions at different levels all may have essential contributions to make—but to determine how institutions at various levels can be vertically linked. Linking institutions vertically is a challenge because of the different objectives of governance at different levels. For example, spatially heterogeneous resources create divergent interests in different localities within higher levels of governance, and higher level institutions respond to different economic and political interests than local institutions. Ostrom (1990) proposed a nesting of institutions as a design principle for making needed linkages, but other approaches are also possible. Young and Berkes (Chapters 8 and 9) begin to conceptualize the issues and to propose arrangements that can maintain the benefits of each level of organization.
The case-based research makes it clear that effective resource management institutions adapt to variation and change in the resources they manage and to changes in the resource user groups. However, despite much interest in adaptive management approaches (e.g., Holling, 1978; Lee, 1993; Berkes, Chapter 9), how institutions adapt has not received much systematic research attention. Institutional adaptation and flexibility are likely to become increasingly important for common-pool resource management because of increasing rates of change in the stocks of some resources and in the institutional environment, particularly at the international level. These issues are discussed further in the section on understudied issues at the end of the chapter.
Research on common-pool resource management institutions has made great strides since the 1980s. In the next decade, research can progress further by continuing in established directions and by addressing some key understudied issues. We believe the state of the field is such that an investment in these areas will produce results that are both sound science and useful to practitioners.
We have noted that the field is following a path of development typical for this stage of the science. Progress is likely to accelerate if the research commu-