It took a decade to get to the negotiating table, and it could easily take another to finish the job, but UN talks in New York to safeguard life in the high seas finally begin in earnest Monday.

The stakes could hardly be higher, experts and diplomats agree.

Oceans produce half the oxygen we breathe, regulate the weather, and provide humanity's single largest source of protein.

Without them, Earth would be just another barren rock in the Universe.

And yet humanity has harvested marine species upon which we depend to the edge of extinction, and used the seas as a collective garbage dump.

Climate change, meanwhile, has altered the ocean's basic chemistry in ways that raise the spectre of a mass extinction that scientists say is already underway.

Today, a patchwork of agreements and regulatory bodies govern shipping, fishing, and mineral extraction, while the UN Convention on the Law of the Sea, negotiated in the 1970s, lays out rules for how far a nation's zone of influence extends beyond its shores.

But in what may be the biggest legal loophole in history, geographically speaking, there is no international treaty protecting marine areas beyond national jurisdiction -- that's two-thirds of the surface of the oceans, and half the planet's.

The result has been a kind of aquatic "Far West", a case study for what has sometimes been called the tragedy of the commons.

"Very early we decided that the high seas were for everybody and nobody, because everyone owns them and nobody takes responsibility for them," said Callum Roberts, a marine biologist at the University of York in England.

- Anything goes -

For most of human history, the vast expanse of open ocean was seen as a distance to travel across rather than a resource to exploit.

But a global population closing in on 10 billion, along with lethally efficient advances in technology, have created the will and the way to pillage marine flora and fauna as never before.

Currently, about 12 percent of the 90 million tonnes of fish harvested every year come from the high seas, but that percentage could climb quickly.

"On the high seas, anything goes," said a European diplomat who will take part in the talks.

"The aim of this future agreement is precisely to set up a system of governance to constrain the impact of human activity," he said, requesting anonymity.

The meeting Monday of the "preparatory committee" is the first of four two-week sessions scheduled through the end of 2017.

That is when members of the United Nations will decide if they have a foundation for negotiating a legally binding treaty which could -- if the history of UN climate talks is any guide -- take a long time.

As with the two-decade wrangle over how to tackle global warming, which finally yielded a universal deal in December, a half-dozen key issues divide nations grouped in familiar blocs on how best to manage the high seas.

One is the scope of zones in which industrial fishing and mineral extraction would be curtailed or banned.

"Marine protected areas are one of the strongest tools for safeguarding nature and rebuilding fish stocks," said Roberts.

Currently, just over three percent of oceans -- all within national boundaries -- are off limits to commercial exploitation. The UN Convention on Biodiversity has called for a target of 10 percent by 2020.

- Genetic resources -

But many experts cite the World Parks Congress 2014 recommendation that fully 30 percent of oceans should be set aside as de facto international parks.

Even then, according to a study published last week in the journal Conservation Letters, it may not be enough. The loss of marine life is already so advanced that it would take larger areas to protect biodiversity and prevent some fish stocks from collapsing.

Nations also disagree on what rules to set for exploiting marine genetic resources.

"Right now, there are no rules -- it's 'first come, first serve'," said Julien Rochette, a researcher at the Institute for Sustainable Development and International Relations in Paris.

Only three countries -- the United States, Germany and Japan -- hold 70 percent of patents stemming from marine life, he noted.

Opposed to a "freedom on the high seas" approach on this issue is the principle -- upheld by China and the G77 bloc of developing nations -- that such genetic wealth belongs to the "common heritage of mankind," and should thus be shared out.

How to set up environmental impact assessments, enforcement, and technology transfer will also be on the table in New York.

"This is the last major multilateral negotiation for the environment on the UN agenda," Rochette said.