Researchers at the University of Copenhagen revealed that unchecked global warming would raise the number of oxygen-starved “dead zones” in large areas of the world’s oceans by a factor of 10 or more.

Dead zones are hypoxic (low-oxygen) regions in the ocean, the observed rates of which have been rising since oceanographers started observing them in the 1970s. These take place near inhabited coastlines, where aquatic life including fish, crabs and clams cannot survive. Such zones can be caused through air pollution and runoff of excess nutrients, mainly nitrogen and phosphorus, enter coastal waters and assist fertilize blooms of algae.

Mr. Gary Shaffer of the University of Copenhagen’s Niels Bohr Institute, who led research team at the Danish Center for Earth System Science, said that if large areas of the world’s oceans will become oxygen depleted (dead zones), it would cause more fish and shellfish deaths.

The study appeared in the journal ‘Nature Geoscience’.

Shaffer stated that dead zones in coastal areas can be diminished by putting control over the fertilizers use.

At the same time, he also said that expanded dead zones, which took place by global warming, will stay for thousands of years and have negative long-standing effects on ocean ecosystems.

“The future of the ocean as a large food reserve would be more uncertain,” Shaffer added.

A 2008 study, which was published in the journal Science, showed that the number of dead zones worldwide has approximately doubled each decade since the 1960s.

Dead zones off the coast of Oregon and Washington are expected to be connected to global warming.