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Ocean Life Facing Mass Extinction–Time For Change Is Now

By Kim Robson:

A groundbreaking new study published last month in the journal Science shows that ocean life is facing an

picture from http://www.buckinghampost.com
picture from http://www.buckinghampost.com

unprecedented level of damage and possible mass extinction. A team of scientists analyzed data from hundreds of sources, including discoveries in the fossil record and statistics on modern container shipping, fish catches, and seabed mining, creating a clearer overall picture of the ocean’s health. Much of this data already existed but had never been analyzed side by side.

“We may be sitting on a precipice of a major extinction event,” said Douglas J. McCauley, one of the study’s authors and an ecologist at the University of California, Santa Barbara.

Humans are harming the oceans far more than we realized. Some ocean species have been heavily overharvested, leading to the rapid influx of fish farms, which are expected to provide most of the fish we eat within the next 20 years. But even greater damage results from large scale habitat loss. Coral reefs, for example, have declined by 40% worldwide, not in small part due to climate-change-driven warming.

Carbon emissions are altering the chemistry of seawater, making it more acidic. “If you cranked up the aquarium heater and dumped some acid in the water, your fish would not be very happy,” said Malin L. Pinsky, a marine biologist at Rutgers University a co-author of the report. “In effect, that’s what we’re doing to the oceans.”

bottom-trawlingBottom trawlers employ large nets to scrape the sea floor, virtually sterilizing 20 million square miles of seabed and destroying sections of the continental shelf. While it’s a victory that whales are no longer widely hunted, they now are suffering collisions more often with container ships.

Mining operations also have the ability to destructively transform the ocean environment. Seabed mining contracts now encompass 460,000 square miles of underwater land, up from zero in 2000. Seabed mining would ruin unique and fragile ecosystems, and introduce pollution to the deep sea.

Some species are already migrating to cooler waters. Black sea bass, once common off the coast of Virginia, have begun appearing up north in New Jersey. Less fortunate species may not be able to find new ranges. Marine reserves will have to be designed with climate change in mind, so that species escaping high temperatures or acidity will be able to find a place to go. “It’s creating a hopscotch pattern up and down the coasts to help these species adapt,” Dr. Pinsky said.

Over the past 500 years, biologists have recorded 514 animal extinctions on land. But documented marine extinctions are far more rare. Nonetheless, the fossil record shows that global disasters have wrecked the seas in the past. Many of the marine species that have become extinct or endangered depend on land for survival — for example, seabirds that nest on cliffs, or sea turtles that lay their eggs in beach sand.

Luckily, there is still time for humans to halt the damage, Dr. McCauley noted, if we implement effective programs limiting ocean exploitation. “There are a lot of tools we can use,” he said. “We better pick them up and use them seriously.” Compared with the continents, the oceans are still wild enough to bounce back to ecological health.

Limiting ocean industrialization to specific regions could allow threatened species to recover in other ones. Slowing extinctions in the oceans will mean reducing carbon emissions, not just adapting to them. “We’re lucky in many ways,” remarked Dr. Pinsky. “The impacts are accelerating, but they’re not so bad we can’t reverse them.”

About Kim Robson

Kim Robson lives and works with her husband in the Cuyamaca Mountains an hour east of San Diego. She enjoys reading, writing, hiking, cooking, and animals. She has written a blog since 2006 at kimkiminy.wordpress.com. Her interests include the environment, dark skies, astronomy and physics, geology and rock collecting, living simply and cleanly, wilderness and wildlife conservation, and eating locally.

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One comment

  1. My name is Joe and I am currently a fisheries student at university. I would like to comment on the depiction of bottom trawling in the article above.
    First, it is true that bottom trawl nets stir up the sea floor and cause mud clouds. This is due to the otter doors that scrape along the seabed, creating the dust cloud to provide a herding effect so it maximizes the fishing area. That, however, is all it stirs up. If pollutants are in the mud and dirt, they must have already been settled on the ocean floor from another source. While it is true also that trawl nets scar the sea bed, it has been shown that the scars often cover themselves back up with natural tidal currents the blow sand and dirt around in the ocean. Also, I am interested in knowing where you discovered the part about the clouds being seen from space, as bottom trawls are at the bottom of the ocean, literally on the seabed, and it is difficult to see to the bottom of the ocean from space. If you are referring to satellite images specifically focusing in on the trawl nets, I may be able to understand that.
    Second, yes, trawl nets can be very large, and yes, they do catch whatever is caught in the codend (the narrow end of the net where the catches are retained). Several trawl nets, however, use Excluder Devices, such as the Eliminator Trawl that is adapted to focus on fish behavior to catch haddock instead of cod, Turtle/Seal Excluder devices that prevent marine mammals from entering the net and push them out, and the mesh sizes are regulated to only catch certain sizes of fish. These are all ways the bycatch is being reduced and prevented.
    Regarding the statement that trawl nets destroy coral reefs, I suppose they could, but trawl nets would become tangled and stuck on the coral, they would not be able to be towed fast enough for it to be efficient, and they work best on soft substrate bottoms, not rocky/coral bottoms. If a fisherman decides to risk the impact and trawl over coral, they would most likely use rockhoppers on the footrope to glide and bounce over the coral.
    Lastly, I cannot say much about whales running into ships, but if they were to run into tow wire, many designs are equipped with weak links to break away under certain pressure, like a whale running into the line. Then, if the net become ghost gear, it more often than not is balled up by oceanic currents and rests somewhere stable, where it becomes home for algal growth and eggs laid by fish.
    Thank you for the interesting article and for raising awareness on the dangers of human impact on the oceans.

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