Only the world's biggest economies top the bounty of the seas. According to a new report by the World Wildlife Fund, the world's oceans are worth a whopping $24 trillion. If the ocean was a country, it would be the seventh largest economy.

Scientists at WWF, with help from researchers at the University of Queensland's Global Change Institute and the Boston Consulting Group, calculated the economic numbers by quantifying the ocean's assets -- including good and services like fisheries, tourism and coastal protections.

Researchers placed the annual value of the ocean's goods and services at $2.5 trillion. But the report claims the ocean's health, and therefore its economic value, is declining.

"Our oceans are the planet's natural capital, a 'factory' producing an incredible array of goods and services that we all want and need," Brad Ack, senior vice president for oceans at WWF, explained in a press release. "But every day we are degrading, over-consuming, and polluting this productive asset to a point of ever diminishing returns."

Especially vulnerable are coral reefs, researchers say. Reefs anchor large and diverse food chains, supporting valuable and productive fisheries, as well as provide protections against erosion and storm surges.

Report authors say pollution, global warming and over-exploitation are the factors putting the world's oceans most at risk.

"The ocean rivals the wealth of the world's richest countries, but it is being allowed to sink to the depths of a failed economy," said Marco Lambertini, the director general of WWF International. "As responsible shareholders, we cannot seriously expect to keep recklessly extracting the ocean's valuable assets without investing in its future."

In order for the ocean to continue offering such tremendous economic value, scientists argue world leaders need to do more to counteract climate change, as well as protect habitat and more diligently manage fisheries.