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RECOGNIZING THE LIMITS

The ocean inspires awe; its vast expanse of water spans most of the earth's surface and fills the deep basins between continents. From the surface, the ocean appears uniform and limitless, seemingly too immense to feel the impacts of human activities. These perceptions led to the philosophy expressed by Hugo Grotius, a Dutchman in the 1600s, that the seas could not be harmed by human deeds and therefore needed no protection. His thinking established the principle of “freedom of the seas,” a concept that continues to influence ocean policy despite clear evidence that human impacts such as overfishing, habitat destruction, drainage of wetlands, and pollution disrupt marine ecosystems and threaten the long-term productivity of the seas.

The flaw in the reasoning expressed by Grotius has been uncovered by research on the biology, chemistry, geology, and physics of the ocean. The sea is not a uniform, limitless expanse, but a patchwork of habitats and water masses occurring at scales that render them vulnerable to disturbance and depletion. The patchiness of the ocean is well known by fishers who do not cast their nets randomly but seek out areas where fish are abundant. There has been an increase in technology and fishing capacity that has led to a corresponding increase in the number of overfished stocks. Destruction of fish habitat as the result of dredging, wetland drainage, pollution, and ocean mining also contributes to the depletion of valuable marine species. As human populations continue to grow, so too does the pressure on all natural resources, making it not only more difficult, but also more critical to achieve sustainability in the use of living marine resources. These concerns have stimulated interest in and debate about the value and utility of approaches to marine resource management that provide more spatially defined methods for protecting vulnerable ocean habitats and conserving marine species, especially marine reserves and protected areas. Based on evidence from existing marine area closures in both temperate and tropical regions, marine reserves and protected areas will be effective tools for addressing conservation needs as part of integrated coastal and marine area management.

MANAGING MARINE RESOURCES

Management of living marine resources presents numerous challenges. The conventional approach typically involves management on a species-by-species basis with efforts focused on understanding population-level dynamics. For example, most fisheries target one or a few species; hence, managers and researchers have concentrated their efforts on understanding the population dynamics and effects of fishing on a species-by-species basis. Although this approach seems less complex, it does not resolve the difficulties of either managing multiple stocks or accurately assessing the status of marine species. This is compounded by the relative inaccessibility of many ocean habitats, the prohibi-



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