Depressing reading.
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.
A report compiled during an April meeting in Oxford of 27 of the world's top ocean experts says that dying coral reefs, biodiversity ravaged by invasive species, expanding open-water 'dead zones', toxic algae blooms and the massive depletion of big fish stocks are all accelerating.
Sponsored by the International Programme on the State of the Ocean, 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 affecting 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 humans' activity: global warming, acidification and 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 begun 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,' Professor Rogers said.
'That degradation is now happening at a faster rate than predicted.'
Indeed, the pace of change is tracking or has surpassed the worst-case scenarios laid out by the UN Intergovernmental Panel on Climate Change 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 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 some 50% of deep-sea life was wiped out, the report said.
Pollution has also taken a heavy toll, rendering the oceans less resilient to climate change.
Run-off from nitrogen-rich fertiliser, 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.
