June 21, 2011
World’s Oceans Face ‘Shocking’ Decline, Mass Extinction
The world's oceans are declining much faster than previously believed, a consortium of ocean experts warned on Monday.
Ocean life is "at high risk of entering a phase of extinction of marine species unprecedented in human history," the scientists said in their report, blaming the problem on pollution, overfishing and other man-made causes that are acting simultaneously in ways not seen before.The panel of 27 of the world's top ocean experts said these conditions are pushing the oceans to the brink of a mass extinction of marine life unseen for tens of millions of years.
Dying coral reefs, biodiversity devastated by invasive species, growing open-water "dead zones," toxic algae and a vast depletion of big fish stocks are all accelerating, the scientists warned in their report, which was compiled during an April meeting in Britain.
Sponsored by the International Programme on the State of the Ocean (IPSO), the analysis was based on a review of recent science, and concluded that ocean health has declined further and faster than the most ominous forecasts of only a few years ago.
All five of Earth's mass extinctions of life were preceded by many of the same conditions now impacting the ocean environment, the experts said.
"The results are shocking," said co-author Alex Rogers, an Oxford professor and head of the IPSO.
"We are looking at consequences for humankind that will impact in our lifetime," Rogers told the AFP news agency.
The scientists identified three primary drivers that are sickening the global marine environment: global warming, acidification and a dwindling level oxygen, a condition known as hypoxia. All three are a direct consequence of human activity.
Until now, these and other factors have typically been studied individually, in isolation. It has only been recently that scientists have started looking at how these forces interact.
"We have underestimated the overall risks, and that the whole of marine degradation is greater than the sum of its parts," Rogers told AFP.
"That degradation is now happening at a faster rate than predicted."
The chain reaction leading to increased acidification of the oceans starts with a vast influx of carbon into Earth's climate system.
The oceans, which act as a massive sponge, absorb more than a quarter of the carbon dioxide people emit into the atmosphere.
However, when the sponge becomes too saturated, it can disrupt the delicate balance of the ecosystems upon which marine life depends.
"The rate at which carbon is being absorbed is already far greater now than during the last globally significant extinction of marine species 55 million years ago," when roughly half of deep-sea life was wiped out in an event known as the Paleocene-Eocene Thermal Maximum (PETM), the experts said.
Pollution has also caused the oceans to be less resilient to climate change. Indeed, runoff from nitrogen-rich fertilizer, toxic microbes and hormone-disrupting chemicals have all contributed to the mass die-off of corals, which are vital for marine ecosystems and hundreds of millions of people.
Meanwhile, the harvesting up to 90 percent of some species of large fish and sharks has significantly disrupted food chains throughout the ocean, leading to imbalanced growth of algae, jellyfish and other "opportunistic" flora and fauna.
"We now face losing marine species and entire marine ecosystems, such as coral reefs, within a single generation," co-author Daniel Laffoley told the AFP news agency.
"And we are also probably the last generation that has enough time to deal with the problems," he said.
On the Net: