By Kim Robson:
A groundbreaking new study published last month in the journal Science shows that ocean life is facing an
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 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.”