Map shows toll on world's oceans

[Matt Rogers]

Whoa nelly.

Only about 4% of the world's oceans remain undamaged by human activity, according to the first detailed global map of human impacts on the seas.

A study in Science journal says climate change, fishing, pollution and other human factors have exacted a heavy toll on almost half of the marine waters.

Only remote icy areas near the poles are relatively pristine, but they face threats as ice sheets melt, they warn.

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Complex model

The international team of 20 scientists in the US, Canada and UK built a complex model to handle large amounts of information on 17 different human threats.

They divided the world's oceans into 1km-square sections and examined all real data available on how humankind is influencing the marine environment.

They then calculated "human impact scores" for each location, presenting this as a global map of the toll people have exacted on the seas.

The researchers say they were shocked by the findings.

"I think the big surprise from all of this was seeing what the complete coverage of human impacts was," said Dr Spalding, senior marine scientist at the conservation group, The Nature Conservancy, in Newmarket, UK. "There's nowhere really that escaped. It's quite a shocking map to see."

He said the two biggest drivers in destroying marine habitats were climate change and over-fishing.

"Out on the high seas, climate change and fishing were far and away the strongest influences," he explained. "The least impacted areas are the polar regions but they are not untouched."

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BBC NEWS | Science/Nature | Map shows toll on world's oceans