From: Romi Elnagar <bluesapphire48@yahoo.com>
Date: Fri, Jun 24, 2011 at 1:41 AM
Subject: [bangla-vision] GOOD READ: Scientists ring death knell for Earth's oceans
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Scientists ring death knell for Earth's oceans The pace of the decline surpasses worst-case scenarios laid out by UN Climate Change panel Agence France-Presse and Reuters All five mass extinctions of life on the planet have been preceded by many of the same conditions now afflicting the ocean environment, including pollution such as this garbage near Manila, says a recent massive review by the world's top ocean experts. Pollution and global warming are pushing the world's oceans to the brink of a mass extinction of marine life unseen for tens of millions of years, a consortium of scientists has warned. Dying coral reefs, biodiversity ravaged by invasive species, expanding open-water "dead zones," toxic algae blooms, the massive depletion of big fish stocks -all are accelerating, they said in a report compiled during an April meeting in Oxford of 27 of the world's top ocean experts. Sponsored by the International Program on the State of the Ocean (IPSO), the review of recent science found that ocean health has declined further and faster than dire forecasts only a few years ago. These symptoms, moreover, could be the harbinger of wider disruptions in the interlocking web of biological and chemical interactions that scientists now call the Earth system. All five mass extinctions of life on the planet, reaching back more than 500 million years, were preceded by many of the same conditions now afflicted the ocean environment, they said. "The results are shocking," said Alex Rogers, an Oxford professor who heads IPSO and co-authored the report. "We are looking at consequences for humankind that will impact in our lifetime." Three main drivers are sickening the global marine environment, and all are a direct consequence of human activity: global warming, acidification and a dwindling level oxygen, a condition known as hypoxia. Up to now, these and other impacts have been studied mainly in isolation. Only recently have scientists began to understand 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 said. "That degradation is now happening at a faster rate than predicted." The pace of the decline in the oceans is tracking or has surpassed the worst-case scenarios laid out by the UN Intergovernmental Panel on Climate Change (IPCC) in its landmark 2007 report, according to the new assessment. The chain reaction leading to increased acidification of the oceans begins with a massive influx of carbon into Earth's climate system. Oceans act as a massive sponge, soaking up more than a quarter of the CO2 humans pump into the atmosphere. But when the sponge becomes too saturated, it can disrupt the delicately balanced ecosystems on which marine life -and ultimately all life on Earth -depends. "Unless action is taken now, the consequences of our activities are at a high risk of causing, through the combined effects of climate change, over-exploitation, pollution and habitat loss, the next globally significant extinction event in the ocean," it said. "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 some 50 per cent of deepsea life was wiped out, the report said. That event, called the Paleocene-Eocene Thermal Maximum, may be an ancient dress rehearsal for future climate change that could be even more abrupt and more damaging, some scientists fear. Pollution has also taken a heavy toll, rendering the oceans less resilient to climate change. Run-off from nitrogen-rich fertilizer, killer microbes, and hormone-disrupting chemicals, for example, have all contributed to the mass die-off of corals, crucial not just for marine ecosystems but a lifeline for hundreds of millions of people too. The harvesting up to 90 per cent of some species of big fish and sharks, meanwhile, has hugely disrupted food chains throughout the ocean, leading to explosive and 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," said Daniel Laffoley, head of the International Union for Conservation of Nature's (IUCN) World Commission on Protected Areas, and co-author of the report. "And we are also probably the last generation that has enough time to deal with the problems." The study said that over-fishing is the easiest of the problems for governments to reverse -countering global warming means a shift from fossil fuels, for instance, towards cleaner energies such as wind and solar power. "Unlike climate change, it can be directly, immediately and effectively tackled by policy change," said William Cheung of the University of East Anglia. "Over-fishing is now estimated to account for over 60 per cent of the known local and global extinction of marine fishes," he wrote. Among examples of overfishing are the Chinese bahaba that can grow up to two metres long. Prices per kilo for the bahaba's swim bladder -meant to have medicinal properties -have risen from a few dollars in the 1930s to $20,000-$70,000. © Copyright (c) The Vancouver Sun http://www.vancouversun.com/technology/Scientists+ring+death+knell+Earth+oceans/4985332/story.html?id=4985332 |
Palash Biswas
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