© Felix Marquez/AP
A fisherman on a beach in Temuco, Chile that is blanketed with dead sardines, a result of algal blooms that suck oxygen out of the water.
Areas starved of oxygen in open ocean and by coasts have soared in recent decades, risking dire consequences for marine life and humanity
Ocean dead zones with zero oxygen have quadrupled in size since 1950, scientists have warned,
while the number of very low oxygen sites near coasts have multiplied tenfold. Most sea creatures cannot survive in these zones and current trends would lead to mass extinction in the long run, risking dire consequences for the hundreds of millions of people who depend on the sea.
Climate change caused by fossil fuel burning is the cause of the large-scale deoxygenation, as warmer waters hold less oxygen. The coastal dead zones result from fertiliser and sewage running off the land and into the seas.
The analysis, published in the journal
Science, is the first comprehensive analysis of the areas and states: "Major extinction events in Earth's history have been associated with warm climates and oxygen-deficient oceans." Denise Breitburg, at the Smithsonian Environmental Research Center in the US and who led the analysis, said: "Under the current trajectory that is where we would be headed. But the consequences to humans of staying on that trajectory are so dire that it is hard to imagine we would go quite that far down that path."
"This is a problem we can solve," Breitburg said. "Halting climate change requires a global effort, but even local actions can help with nutrient-driven oxygen decline." She pointed to recoveries in Chesapeake Bay in the US and the Thames river in the UK, where better farm and sewage practices led to dead zones disappearing.
However, Prof Robert Diaz at the Virginia Institute of Marine Science, who reviewed the new study, said: "Right now, the increasing expansion of coastal dead zones and decline in open ocean oxygen are not priority problems for governments around the world. Unfortunately, it will take severe and persistent mortality of fisheries for the seriousness of low oxygen to be realised."
Comment: The Gulf of Mexico is now the largest dead zone in the world - and we have factory farming to blame for it. Perhaps increased methane outgassing and undersea volcanic activity (it is estimated there are up to one million of these 'submarine volcanoes') are also contributory factors to these devastating 'dead zones'?
The significant increase of fish die off's and strange migratory behaviour of marine life could be considered other potential signs of such activity.