A two degree hike would threaten 50 percent of breeding grounds of emperor penguins, and 75 percent of Adelie penguin colonies, said the study, released by the World Wildlife Fund (WWF) at the World Conservation Congress in Barcelona.

The United Nation's panel of climate change scientists has warned that earth's average temperature could increase more than two degrees Celsius by century's end even if major efforts are made curb greenhouse gases, and twice as fast under "business-as-usual" scenarios.

A reduction in the sea ice is also likely to have a knock-on effect on the abundance of krill, which is a vital food source for penguins, concludes the report.

"Penguins are very well adapted to living in the cold and extreme conditions of Antarctica," said the WWF's Juan Casavelos, noting that warming has already contributed to a reduction in populations.

"If temperatures increase by another two degrees these icons of the Antarctic will be seriously threatened," he said.

A two-degree increase above pre-industrial temperatures is widely viewed among scientists as the threshold beyond which climate change will have severe consequences for Earth's ecosystems, including for humans.

While curbing global warming is the only viable long-term solution, conservationists have called for an expanded network of marine protected areas to reduce pressure on penguins, and for tighter management of krill and finfish fisheries the Southern Ocean.

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