marine ecosystems. However, it is now obvious that the seas feel the stamp of heavy human use from industries such as fishing and transportation, the effects of waste disposal, excess nutrients from agricultural runoff, and the introduction of exotic species. The cumulative effect on marine ecosystems has attracted public attention and enhanced public concern for ocean resources, unique habitats, and the threats to continuing marine ecosystem productivity.
Most of the world's fish stocks are now heavily exploited. As many as 25 to 30% are overfished, and another 44% are fully exploited (Garcia and Newton, 1997; FAO, 1999; NRC, 1999a). In Europe, the impact of fishing on fish population abundance became evident when naval activities and extensive minefields closed the North Sea fishery during World Wars I and II. While catches prior to the wars were declining, there were dramatic recoveries immediately afterwards when it was safe to resume fishing activity (Gulland, 1974; Cushing, 1975). These recoveries supported the idea that time and area closures could be estabfished to restore and protect overfished stocks.
Given the growing perception that current management of marine resources and habitats is insufficient, interest is growing in approaches to ensure the continuing viability of marine ecosystems. Over the past century, concern about the rapid loss of wilderness lands led to establishment of protected areas, reserves, and parks in terrestrial ecosystems where human activities are much restricted or at least curtailed. Generally, the objective in these areas is to protect or restore ecosystems, to preserve the natural beauty of the landscape, and to support the survival of native species. The public accepts these concepts and cherishes protected areas such as national parks and wildlife refuges. Yet this approach has not transferred to the marine environment. The effectiveness of marine reserves and marine protected areas (MPAs) is debated passionately by advocates and detractors, even though more than a thousand MPAs have been established around the globe. Similar to terrestrial protected areas, advocates promote their benefits as insurance against overexploitation, conservation of biodiversity, and protection of habitat. Their potential as tools for fisheries management is recognized by many scientists (Bohnsack, 1998). However, few MPAs have been evaluated critically to determine to what extent they benefit exploited species.
There have been numerous attempts to develop terms and definitions to encompass the array of applications of MPAs in marine conservation. In principle, the committee accepts the classification scheme developed by the International Union for the Conservation of Nature and Natural Resources (IUCN, see Appendix F) which applies to both terrestrial and marine protected areas (IUCN, 1994). The six categories in this scheme provide a mechanism for assessing the status of protected areas internationally. However, the specificity provided by the IUCN classification makes it impractical for quick reference to the more general goals of MPAs described in this report. Therefore, the committee defined a simplified list of terms for the various types of protected areas, listed here in order of increasing levels of protection: