HANOI  - The future food security of millions of people is at risk because over-fishing, climate change and pollution are inflicting massive damage on the world’s oceans, marine scientists warned this week.

The two-thirds of the planet covered by seas provide one fifth of the world’s protein — but 75 percent of fish stocks are now fully exploited or depleted, a Hanoi conference that ended Friday was told.

Warming seas are bleaching corals, feeding algal blooms and changing ocean currents that impact the weather, and rising sea levels could in future threaten coastal areas from Bangladesh to New York, experts said.

“People think the ocean is a place apart,” said Peter Neill, head of the World Ocean Observatory. “In fact it’s the thing that connects us — through trade, transportation, natural systems, weather patterns and everything we depend on for survival.”