Covering almost three-quarters of the planet, the ocean plays an essential role in supporting life on Earth. This is particularly true of the high seas—the massive area beyond the boundaries of any country. These waters, which account for nearly two-thirds of the world’s ocean, provide ecosystem benefits that extend to every corner of the globe. The high seas are responsible for nearly half of the ocean’s biological productivity,1 and their health is closely linked to the health and resilience of coastal regions.2
At the same time, the human impact on these waters is increasing in range and intensity. This escalation means that the international community needs an array of tools to counter threats to ocean life beyond national boundaries.
Currents carry tons of plastics and other debris thousands of kilometers from shore into the open ocean, where the waste can harm marine organisms and fundamentally change the way healthy ecosystems function. Industrial-scale fishing is also taking a toll. Worldwide, some 4 million vessels catch more than 90 million metric tons of fish every year. This activity has led to a global decline of fisheries; 90 percent are either depleted or fully exploited.3 To make matters worse, new technologies, such as those used for deep-sea bottom trawling or more efficient fish aggregating devices, are degrading important ocean habitats and increasing bycatch. Climate change and emerging uses of the ocean, including oil and gas exploration and extraction in the deep sea and seabed mining, also pose major risks.
Because of the interconnected nature of ocean ecosystems, declines on the high seas will bring corresponding declines in coastal ecosystems. For example, over 40 percent of commercially important fish species are caught both in coastal waters and on the high seas. As a result, overexploitation of marine life on the high seas will ultimately reduce catches along the coasts and degrade coastal food webs and ecosystems.4 And any harm to coastal fisheries can have significant implications for food security. More than 4 billion people worldwide depend on fish as a key source of animal protein.5
Fully protected marine reserves are among the management tools available to help address some of the critical challenges to ocean health. Like national parks on land, these reserves protect ocean areas from extractive and destructive human activities to conserve species, habitats, and ecosystem processes. To date, though, only 1 percent of the world’s ocean has been fully protected. Even less of the high seas is highly protected, in large part because no overarching laws exist to allow countries to establish reserves that will be universally recognized and respected in waters beyond national jurisdictions.
Scientists see marine reserves as critical tools for safeguarding biodiversity, habitats, and crucial ecosystem processes. Research shows that reserves boost ecological resilience against environmental stressors occurring across the globe, such as overexploitation of resources, climate change, and ocean acidification.
Marine reserves have proved to:
Recent science also shows that the cumulative impact of human activities matters to ocean ecosystems and that reserves yield the greatest conservation benefits when they are large, highly protected, isolated, well-enforced, and long-standing. The benefits increase exponentially when all five features are in place. For example, marine protected areas with all of these characteristics have 14 times as much shark biomass, twice as many large fish, and five times as much fish biomass than fished areas. In comparison, marine protected areas with only one or two of these characteristics were largely indistinguishable from fished areas.11
Negative human influences touch every part of the ocean, but the harm can be reversed.
Fully protected marine reserves can help conserve biodiversity and valuable habitats that maintain ecosystem function and counter environmental change. A system of marine reserves on the high seas would protect the unique marine life in these waters, as well as the interconnected coastal and ocean ecosystems beyond.