Reporter: Jane CowanELIZABETH JACKSON: If you thought the drought ravaging Australia was the worst manifestation of climate change, think again.
The Pacific Ocean lapping our shores is in trouble, according to an international group of scientists.
The marine biologists say the Pacific Ocean is facing ecological peril, with half of the sea's biodiversity now at risk.
Jane Cowan reports.
JANE COWAN: As a marine scientist and a yachtsman Dr Mark Orams has spent more time than most of us on the open sea.
MARK ORAMS: It's quite something to be on a boat thousands of miles from land. You, of course, are struck by the scale and the grandeur.
JANE COWAN: But through his work at Massey University in New Zealand Mark Orams has come to a slow realisation that all is not well with the largest ocean on the planet. There are worrying signs that weren't there just 15 years ago.
MARK ORAMS: From the moment you get off a small boat and go ashore, you note at the high water mark debris that's been brought ashore, plastic and other human-made products that have been broken down and washed over the hundreds and thousands of miles.
JANE COWAN: Dr Orams is one of 350 researchers from 30 countries who have signed a document they hope will be a wake-up call for the Pacific.
The Pacific Ocean Scientific Statement says that the combined threats of over-fishing, nutrient and sediment run-off, habitat destruction, and climate change are damaging the sea. Populations of some species of large tuna, sharks, and turtles are in decline.
And climate change is already creating pulses of warm water, hypoxic dead zones, and acidic conditions. The effects on small island communities dependent upon fisheries for their livelihoods are obvious.
But an ailing Pacific Ocean stands to affect everyone because of the sea's role in moderating climate change. It's a huge carbon sink, but if the water temperature warms significantly, it actually releases carbon rather than sucking it out of the atmosphere.
MARK ORAMS: They talk about tropical rainforests as being the lungs of the planet; well the ocean is almost the heartbeat.
JANE COWAN: Another signatory to the document is Professor Ove Hoegh-Guldberg, a coral reef biologist specialising in climate change and the director of the Centre for Marine Studies at the University of Queensland.
He says what's needed is an alliance of countries across the Pacific, with Australia playing a leading role.
OVE HOEGH-GULDBERG: Things like helping nations proclaim marine protected areas. How can we help nations fight the scourge of overfishing? There are many, many people in this area who depend on their marine resources for their daily food.
JANE COWAN: But Australia also has room to improve its own behaviour for the sake of the ocean.
OVE HOEGH-GULDBERG: We happen to be the world's highest emitters of CO2 per capita. That particular problem is going to become the most significant problem to the Pacific over the next 50 years ...
ELIZABETH JACKSON: Coral reef biologist Professor Ove Hoegh-Guldberg with Jane Cowan