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Half of All Marine Life Lost in Just 40 Years

Close to one-third of the planet's fish stocks are overfished and one in four species of sharks, rays and skates are threatened with extinction.

In just four decades, marine species have declined by 49 percent, according to one of the most extensive surveys of marine life ever compiled.

The "Living Blue Planet Report," just released by World Wildlife Fund in collaboration with the Zoological Society of London, documents the extraordinary losses, which occurred from 1970 to 2012. Alarmingly, some fish species were found to have declined by almost 75 percent.

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The authors of the report attribute the dramatic population drops to human-driven climate change as well as to habitat loss, overexploitation and pollution.

"In less than a human generation, we can see dramatic losses in ocean wildlife -- they have declined by half -- and their habitats have been degraded and destroyed," Brad Ack, senior vice president for Oceans at WWF, told Discovery News. "Driving all these trends are humans actions: from overfishing and resource depletion, to coastal development and pollution, to the greenhouse gas emissions causing ocean acidification and warming."

The findings were determined after researchers surveyed more than 10,000 populations of 3,038 marine species, including fish, birds, mammals and reptiles. The report estimates that close to one-third of the world's fish stocks are overfished, and 1 in 4 species of sharks, rays and skates are threatened with extinction.

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Several shark species "have declined dramatically around the world due to overfishing," and other human-driven causes, confirmed Mahmood Shivji, director of the Guy Harvey Research Institute at Nova Southeastern University, who was not involved with the study.

Yet another key finding from the report is that three-quarters of the world's coral reefs are currently threatened. At current projected levels of warming and ocean acidification, all coral reefs are projected to be lost by the year 2050.

"Corals are suffering from poor water quality due to deforestation and coastal agriculture, along with increasing fishing pressure on beneficial animals that help them stay healthy, such as reef fish," Ack said.

"Ocean warming from climate change and ocean acidification from excess carbon absorption significantly threaten reefs over the long-term," Ack said. "At current rates of temperature rise, oceans will become too warm for coral reefs by 2050, resulting in the loss of the world's most biologically diverse marine ecosystem."

Currently some coral reefs are able to bounce back from disturbances, such as bleaching events, cyclones and outbreaks of damaging crown-of-thorns starfish. Ocean acidification, however, slows down the ability of corals to recover from these and other threats, adding to the downward trend.

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Ack and his colleagues call for immediate measures to curb the decline, such as ending illegal fishing and protecting coral reefs, mangroves and other critical ocean habitats.

This month, world leaders are meeting at a United Nations summit in New York to develop goals for global sustainable development. Ack said the meeting will provide "an opportunity for the international, concerted action we need for ocean conservation." Ack also said the United Nations Conference on Climate Change, to be held later this year in Paris, was an opportunity to "slash the emissions contributing to the climate and ocean crisis."

In the report, Marco Lambertini, director-general of WWF International, wrote that "humanity is collectivity mismanaging the ocean to the brink of collapse."

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"Considering the ocean's vital role in our economies and its essential contribution
to food security -- particularly for poor, coastal communities -- that's simply unacceptable," he added. "Could the economic implications of the collapse of the ocean's ecosystems trigger the next global recession or undermine the progress we have made on eradicating poverty?"

Lambertini concluded, "We can and we must correct the current course now."

A school of bigeye trevallies swim by the Liberty Wreck in Tulamben, North Bali, Indonesida.

Expansion of the Pacific Remote Islands Marine National Monument establishes 490,000 square miles of protected tropical marine habitat. This will benefit its many species ranging from delicately beautiful corals to toothsome sharks. President Obama designated the expansion this week because science has shown that large marine protected areas can help rebuild biodiversity, support fish and other marine populations, and improve overall ecosystem resilience. The Pacific Remote Islands Marine National Monument is now the largest marine reserve in the world. Greg Stone, executive vice president and chief scientist for Conservation International, told Discovery News, "The national monument shares a maritime border with the Republic of Kiribati, one of which is adjacent to the Phoenix Islands Protected Area, another protected area which, as of January 1, 2015, will be closed to commercial fishing." That is good news for this blacktip shark, photographed in the region. Both it and the prey it hunts will gain protection.

This manta ray was also photographed in the south-central Pacific. Manta rays frequently have been killed, both directly and indirectly, by fisheries. Closure to commercial fishing in the region will prevent manta rays from being captured with nets, trawls, harpoons and more.

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Gentle green sea turtles are endangered, so protection of their habitat is all the more crucial. They must migrate long distances between feeding grounds and hatching beaches, putting them at risk throughout the journeys. Hopefully the newly expanded marine reserve will help to stabilize their populations.

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Many different kinds of sharks exist in the south-central Pacific, including the bull shark. It is near threatened so, as for green sea turtles, extra protection is needed to increase the shark's numbers.

The marine reserve, Stone said, "is a part of the ocean that is home to some of the largest tuna stocks in the world. Expanding the area of the monument will help fish stocks recover to a healthy level, which is vital in order to meet the food needs for the growing world population."

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Reef fish such as the Napoleon wrasse, the bohar snapper and the long-nosed parrotfish, shown here, will gain protection, according to Stone. The Waitt Foundation and Oceans 5 recently pledged $5 million dollars to support the Phoenix Islands Protected Area. Stone said that such private support remains essential because the marine reserve includes many developing nations. They are leading conservation projects, but require funding in order to ensure the long-term success of their efforts.

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Marine mammals often travel long distances, requiring widespread protected regions to ensure their safety. As Stone explained, "Sea turtles, sharks, whales, dolphins and seabirds travel through this (south-central) part of the Pacific, and protected areas can help conserve these marine animals and strengthen the marine ecosystem in the Pacific."

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Habitat for several frigatebirds exists within the Pacific Remote Islands Marine National Monument, according to Stone. Frigatebirds are a family of seabirds that tend to be large and with iridescent black feathers. Major nesting populations of this particular species, the great frigatebird, are found in the Pacific.

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Both the Phoenix Islands Protected Area and the expanded marine reserve declared by the Obama administration are home to over 50 species of coral. One of the most distinctive and eye-catching is pearl bubble coral. It's not difficult to see how this beautiful coral got its name.

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Apex ocean predators, such as great white sharks, will gain additional protection too as a result of the announced marine reserve expansion. "The creation of these kinds of marine protected areas and reserves in the ocean help to create safe travel corridors for migratory species, which recognize no boundaries in our oceans," Stone said.

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