Image: Bleached coral
Great Barrier Reef Park  /  AFP - Getty Images file
This section of Australia's Great Barrier Reef in 2009 saw "bleaching" of coral caused by warmer than normal ocean temperatures. Bleaching can kill reefs if it is prolonged. staff and news service reports
updated 6/22/2011 1:14:44 PM ET 2011-06-22T17:14:44

Mass extinctions of species in the world's oceans are inevitable if current trends of overfishing, habitat loss, global warming and pollution continue, a panel of renowned marine scientists warned Tuesday.

The combination of problems suggests there's a brewing worldwide die-off of species that would rival past mass extinctions, the 27 scientists said in a preliminary report presented to the United Nations.

Vanishing species — from sea turtles to coral — would upend the ocean's ecosystem. Fish are the main source of protein for a fifth of the world's population and the seas cycle oxygen and help absorb carbon dioxide, the main greenhouse gas from human activities.

"Things seem to be going wrong on several different levels," said Carl Lundin, director of global marine programs at the International Union for Conservation of Nature, which helped produce the report with the International Programme on the State of the Ocean.

Some of the changes affecting the world's seas — which have been warned about individually in the past — are happening faster than the worst case scenarios that were predicted just a few years ago, the report said.

"It was a more dire report than any of us thought because we look at our own little issues," Lundin said. "When you put them all together, it's a pretty bleak situation."

Climate and coral
Coral deaths alone would be considered a mass extinction, according to study chief author Alex Rogers of the University of Oxford. A single bleaching event in 1998 killed one-sixth of the world's tropical coral reefs.

Lundin pointed to deaths of 1,000-year-old coral in the Indian Ocean and called it "really unprecedented."

"Not only are we already experiencing severe declines in many species to the point of commercial extinction in some cases, and an unparalleled rate of regional extinctions of habitat types (e.g. mangroves and seagrass meadows), but we now face losing marine species and entire marine ecosystems, such as coral reefs, within a single generation," the experts said.

The chief causes for extinctions at the moment are overfishing and habitat loss, but global warming is "increasingly adding to this," the report said.

Carbon dioxide from the burning of fossil fuels ends up sinking in the oceans, which then become more acidic, devastating sensitive coral reefs. Warmer ocean temperatures also are shifting species from their normal habitats, Rogers said. Non-native species moving into new areas can cause havoc to those ecosystems.

Jelle Bijma, of the Alfred Wegener Institute, said the seas faced a "deadly trio" of threats of higher temperatures, acidification and lack of oxygen that had featured in several past mass extinctions.

Runoff from fertilizers into rivers and seas has reduced oxygen in those areas, creating dozens of "dead zones" around the globe. The U.S. Geological Survey earlier this month said it expects the dead zone from the Mississippi River to set a record when it builds later this summer due to flooding runoff.

"From a geological point of view, mass extinctions happen overnight, but on human timescales we may not realize that we are in the middle of such an event," Bijma wrote.

Chemicals and plastics from daily life also are causing problems for sea creatures, the report said. Overall, the world's oceans just cannot bounce back from problems — such as oil spills — like they used to because of all the compounding factors, scientists said.

Confounding the most dire predictions, the Gulf of Mexico has bounced back from last year's major oil spill, but it is still dealing with the growing "dead zone" and above average sea temperatures.

Similar 'stressors' in past extinctions
Describing the multiple events affecting the world's oceans as high intensity "stressors," the experts said similar compounding led to the previous five mass extinction events in the past 600 million years — most recently when the dinosaurs vanished 65 million years ago, apparently after an asteroid struck.

Data: The rise and fall of Earth's species (on this page)

The conclusions follow an international meeting this spring in England to discuss the fate of the world's oceans. A full report will be published later this year, the panel said.

Lundin said that "some of these things are reversible if we change our behavior."

Overfishing is the easiest for governments to address, the experts said.

"Unlike climate change, it can be directly, immediately and effectively tackled by policy change," said William Cheung of the University of East Anglia. "Overfishing is now estimated to account for over 60 percent of the known local and global extinction of marine fishes."

Among examples of overfishing are the Chinese bahaba. Its swim bladder is desired in Asia as a medicinal product, and the cost per kilo (2.2 pounds) has risen from a few dollars in the 1930s to $20,000-$70,000 today.

Listed as critically endangered, the bahaba is just one of more than 500 marine species threatened by overfishing, Cheung noted. "The only chance for many of these species to recover is to stop overfishing and protect them so that the populations can rebuild," he added.

"If action is not taken immediately, our generation will see many more species follow the footsteps of the Chinese bahaba," Cheung said.

Fisheries improvement ignored?
On fisheries, at least, the report had some critics.

"It ignores all of the recent fisheries research showing stability or even recovery in fish populations as overfishing is reversed in many areas," said Trevor Branch, a University of Washington fishery sciences assistant professor.

He said he could only find one expert on the panel working on fisheries,  Daniel Pauly of Canada's University of British Columbia, "and his inclination to apocalyptic rhetoric is well known."

Steve Murawski, a University of South Florida professor and previously chief science advisor for the U.S. National Marine Fisheries Service, said that "it's difficult to judge the veracity of the results or the scientific support" for the findings because the full report hasn't been published.

But he noted that in the United States "a strong set of management requirements backed by the force of law have resulted in an end to domestic overfishing."

"This is of course a very hopeful sign because the USA is such an important fishing nation," he added. "Is the record commensurate globally? No it is not, and thus I would certainly support" the panel's advice to reduce global fishing "to levels commensurate with long-term sustainability of fisheries and the marine environment."

The Associated Press and Reuters contributed to this report.

Video: Biologist: 'Epic' decline of aquatic life

Photos: Census of Marine Life

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  1. Census of the seas

    The Census of Marine Life has issued its final report on the 10-year effort to document the diversity of the world's oceans. More than 2,700 scientists cataloged 28 million observations of new species as well as old favorites such as the octopus. This octopus specimen was collected at Lizard Island on Australia's Great Barrier Reef in an Autonomous Reef Monitoring System, or ARMS, at a depth of 30 to 36 feet (10 to 12 meters). The ARMS system is one of the legacies of the census. (Julian Finn / Museum Victoria) Back to slideshow navigation
  2. Jam-packed jellyfish

    The ultimate role of a jellyfish is to reproduce. The brown granular core in this jelly, Bouganvillia supercilliaris, is stuffed to the breaking point with hundreds of eggs. (Russ Hopcroft / Univ. of Alaska-Fairbanks / COML) Back to slideshow navigation
  3. Tree of the sea

    This Christmas tree worm (Spirobranchus giganteus) was found at Lizard Island on Australia's Great Barrier Reef. (John Huisman / Murdoch Univ.) Back to slideshow navigation
  4. Seal of approval

    A young Weddell seal (Leptonychotes weddellii) gets his final diving lessons. He is already the size of his mother, who is waiting under the water. Soon, he'll be on his own. The Census of Marine Life cataloged marine mammals as well as other types of creatures ranging from fish to microbes. (Galatee Films) Back to slideshow navigation
  5. Floating ... and stinging

    Sea nettles (Chrysaora fuscescens) float in the water of California's Monterey Bay. The nettle's sting is deadly to small prey but not potent enough to kill humans - except in the case of an allergic reaction. (Richard Hermann / Galatee Films) Back to slideshow navigation
  6. Vampire of the deep

    The vampire squid, also known by the scientific name Vampyroteuthis, is a cephalopod that lives in the oxygen minimum zone of California's Monterey Bay at depths of 2,000 to 3,000 feet (600-900 meters). (Kim Reisenbichler / MBARI) Back to slideshow navigation
  7. Coral complexity

    Researchers with the Census of Marine Life conducted an inventory of octocorals, named for the eight tentacles that fringe each polyp. This is a soft coral, Dendronephthya, from the coral gardens off Lizard Island on Australia's Great Barrier Reef. (Gary Cranitch / Queensland Museum) Back to slideshow navigation
  8. A string of stomachs

    This physonect siphonophore (Marrus orthocanna) was photographed during NOAA’s "Hidden Ocean Expedition." The colonial animal is made up of many repeated units, which include tentacles, and multiple stomachs. Many specimens were observed at depths between 1,000 and 5,000 feet (300 to 1,500 meters). (Kevin Raskoff / COML) Back to slideshow navigation
  9. Long-haired crab

    South of Easter Island, the Census of Marine Life's vent explorers discovered a crab so unusual it warranted a whole new family designation, Kiwidae. Beyond adding a new family to the wealth of known biodiversity, its discovery added a new genus, Kiwa, named for the mythological Polynesian goddess of shellfish. Its furry or hairy appearance justified its species name, hirsuta. (A Fifis / Ifremer via AP) Back to slideshow navigation
  10. Painful beauty

    This type of anemone lives in a mucous tube on the muddy bottoms of coastal waters, estuaries and soft seabeds. They're found in tropical and subtropical waters throughout the world, where they can grow up to 6 inches (15 centimeters) across and a foot (30 centimeters) tall. When the anemone is threatened, the animal retracts into its tube for protection. The beautiful stinging tentacles of the tube anemone vary from a vibrant purple to a creamy brown. (Karen Gowlett-Holmes / COML) Back to slideshow navigation
  11. Two little urchins

    Bottom-dwelling animals often release their larvae into the water for feeding and dispersal as "meroplankton." These two larvae from Russia's Chukchi Sea measure less than a tenth of an inch (1 millimeter) but will eventually grow into sea urchins or sand dollars. (Russ Hopcroft / Univ. of Alaska-Fairbanks / COML) Back to slideshow navigation
  12. The single snail

    This snail (Alviniconcha sp.) inhabits deep-sea hydrothermal vents along the Suiyo Seamount, off the coast of Japan. It's probably a new species, and only a single specimen has been discovered to date. Where are its peers? (Yoshihiro Fujiwara / JAMSTEC) Back to slideshow navigation
  13. Snazzy snail

    The flamingo tongue snail, Cyphoma gibbosum, was photographed near Grand Cayman in the British West Indies, and is listed in the Gulf of Mexico biodiversity inventory. (Kacy Moody / COML) Back to slideshow navigation
  14. Behold the squidworm

    In October 2007, U.S. and Filipino scientists traveled to the Celebes Sea in Southeast Asia, searching for new species living in its deep water. When they discovered this extraordinary worm — which they named "Squidworm" — they knew they had something special. (Laurence Madin / WHOI) Back to slideshow navigation
  15. Fragile star

    The acantharians are one of the four types of large amoebae that occur in marine open waters. Their fragile skeletons are made of a single crystal of strontium sulfate that quickly dissolves in the ocean water after the cell dies. (Linda Amaral Zettler / MBL (micro*scope)) Back to slideshow navigation
  16. Green banners

    Nereocystis, a marine alga commonly referred to as bull kelp, is often found in the nearshore and shallow gulf areas of North America's Pacific Coast. (Brenda Konar / COML) Back to slideshow navigation
  17. Flea gets its close-up

    Hyperoche capucinus is a common sand flea that swims in polar waters. This specimen is about the width of a finger. (Russ Hopcroft / Univ. of Alaska-Fairbanks / COML) Back to slideshow navigation
  18. A different kind of flytrap

    This striking creature, a Venus flytrap anemone (Actinoscyphia sp.), was photographed in the Gulf of Mexico. The anemone is so named because it resembles the land-based Venus flytrap, a carnivorous plant. (Ian Macdonald / Florida State University) Back to slideshow navigation
  19. Alien in earthly waters

    Gary Cranitch's photographs for CReefs were recognized for excellence by the Australian Institute of Professional Photographers. This spectacular jellyfish inhabits the water of Australia's Great Barrier Reef off Lizard Island. (Gary Cranitch / Queensland Museum) Back to slideshow navigation
  20. Seaweed? Look again

    The leafy seadragon, Phycodurus eques, is camouflaged to resemble a piece of drifting seaweed. (Karen Gowlett-Holmes / COML) Back to slideshow navigation
  21. Pretty in pink?

    This pink see-through fantasia, Enypniastes, is a swimming sea cucumber seen about a mile and a half (2,500 meters) deep in Southeast Asia's Celebes Sea. (Laurence Madin / WHOI) Back to slideshow navigation
  22. A golden lace nudibranch, Halgerda terramtuentis, was collected in the waters of the northwestern Hawaiian Islands. (Cory Pittman / NOAA / PIFSC / NHIMN) Back to slideshow navigation
  23. Red jelly

    This specimen of the jellyfish species known as Crossota norvegica was collected from the deep Arctic Canada Basin with a remotely operated vehicle. (COML) Back to slideshow navigation
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  1. Julian Finn / Museum Victoria
    Above: Slideshow (23) Wonders from the Census of Marine Life
  2. Francesco Zizola / Consequences by NOOR
    Slideshow (11) Rising ocean levels threaten Maldives


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