Sick oceans threaten NZ's seas

Whales are at high risk of extinction. Photo / Ingrid Visser-Orca Research Trust

Mark Costello New Zealand's marine life will not be spared a looming phase of extinction which scientists have predicted is closer and more alarming than first thought.

An international study has found that fish, sharks and whales are at high risk of an extinction crisis at a scale not seen in human history.

The study by the International Programme on the State of the Ocean (Ipso), which includes research from the University of Canterbury, concludes that mass extinctions are inevitable if human impacts are unchanged.

An interdisciplinary workshop at Oxford University used existing research to measure the collective effect of stresses on the world's oceans including pollution, acidification, ocean warming, over-fishing and oxygen loss.

Ipso's scientific director, Alex Rogers, said the findings were shocking.

"As we considered the cumulative effect of what humankind does to the ocean, the implications became far worse than we had individually realised."

New Zealand marine experts said this country had relatively low pollution and over-fishing problems, but was still vulnerable to mass events.

Coral reef destruction and changes in alkalinity on the other side of the world would eventually hurt New Zealand's marine ecosystems.

Associate Professor Mark Costello of the University of Auckland said acute problems such as over-fishing could be managed at a local level but climate change was far more difficult.

He said depleted fish stocks and dirty oceans were visible, everyday issues easily grasped by government and the public. But inertia around sea and atmosphere temperature change made it harder to spur a groundswell.

"We don't seem to be able to put the brakes on. And that could have impact across whole oceans."

Warming seas could be beneficial to New Zealand fish productivity in the short term but little is known about how the entire food web could be affected.

Ipso found that hypnoxia (low oxygen levels) and anoxia (absence of oxygen), a warming ocean and acidification are the three factors in every mass extinction event in the Earth's history.

The group of 27 scientists noted that the last time these factors combined - 55 million years ago - half of some species of deep-sea animals were wiped out. Ten million years earlier, the same combination meant major planktonic extinction.

Researcher Jelle Bijma said: "At that point there were no humans around, so there was no over-fishing, no pollution and this deadly mix was enough. What we can expect for the future is that it's going to be worse."

Another researcher said the pH levels observed in the oceans had not been seen "since the time of the dinosaurs".

Nutrient run-off from farming is creating "dead zones" in the ocean where fish cannot get enough oxygen.

Some stresses were the result of modern technology. Chemicals from flame retardants and detergents are being found in the Polar seas and are being ingested by marine animals.

The report sets out recommendations for governments and the United Nations to conserve ocean ecosystems and urges better governance of the high seas.

THE SITUATION

FINDINGS
* The combination of stresses on the world's oceans is creating conditions comparable to every major extinction in the Earth's history.
* The speed and rate of degeneration have been greater than most scientists predicted in worse-case scenarios.
* The first steps to globally significant extinctions may have already begun.

EFFECTS
* Over-fishing has reduced some commercial fish stocks and populations of by-catch by more than 90 per cent.
* Record high temperatures in 1998 led to mass coral bleaching, killing 16 per cent of all coral reefs.
* Pollutants such as flame retardants are being found in the polar seas and are making their way into marine food chains.