Unchecked global warming may lead to greater ‘dead zones’ in oceans


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Unchecked global warming would lead to a rapid expansion of oxygen-starved “dead zones” in the world’s oceans by a factor of 10 or more, according to researchers at the University of Copenhagen.

Dead zones are low-oxygen areas in the ocean where sea life including fish, crabs and clams cannot survive. In shallow coastal regions, dead zones can be caused by air pollution and runoff of excess fertilizers from farming. The expansion of dead zones would lead to more fish and shellfish deaths, said Gary Shaffer of the University of Copenhagen’s Niels Bohr Institute, who led a team of researchers at the Danish Center for Earth System Science. The study was published online in Nature Geoscience.


While dead zones in coastal areas can be mitigated by controlling the use of fertilizer, expanded dead zones caused by global warming will remain for thousands of years and have harmful long-term effects on ocean ecosystems, Shaffer said.

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

The number of dead zones in coastal waters has doubled every decade since 1960, killing fish, crustaceans and other marine life, according to a 2008 study published in the journal Science.

Dead zones off the coast of Oregon and Washington are likely to be linked to global warming.

--Catherine Ho