Around 70 percent of the world's current king penguin population could face extinction in the near future if proper steps are not taken to constrain climate change, a new study has said.

In a report published in the journal Nature Climate Change, scientists have warned that climate change and overfishing can cause a major reduction in the birds' population. They studied the birds' fragmented population in the Southern Ocean.

The report, titled "Climate-driven range shifts of the king penguin in a fragmented ecosystem," said the species "could disappear" unless urgent steps were taken.

"Our work shows that almost 70 percent of king penguins — about 1.1 million breeding pairs — will have to relocate or disappear before the end of the century because of greenhouse gas emissions," said Céline Le Bohec, co-author of the paper and an ecologist at the French National Centre for Scientific Research (CNRS) and the University of Strasbourg.

"If no actions aiming at halting or controlling global warming, and the pace of the current human-induced changes – climate change, overfishing – stay the same, the species may disappear in the near future," she said.

Le Bochec added: "Unless current greenhouse gas emissions drop, 70 percent of king penguins — 1.1 million breeding pairs — will be forced to relocate their breeding grounds, or face extinction before the end of the century."

The total king penguin population was more than 2 million breeding pairs worldwide just a decade ago, but now it is 1.6 million. And, out of that, nearly 1.1 million birds may be forced to relocate due to increasing forage.

According to the study, their foraging ground — the Antarctic polar front (APF), which is filled with fish and krill — is being pushed further south.

"Penguins, like other seabirds and marine mammals, occupy higher trophic levels in the ecosystems: they are what we call bio-indicators of their ecosystems," she said.

"Thus, penguins, as sensitive indicators of changes in marine ecosystems, are key species for understanding and predicting impacts of global change on the marine biome, and on polar regions for species living in sub-Antarctic and Antarctic areas."

The international team of researchers used computer modeling to study the king penguins' habitat and where they can shift in the near future. Their research also looked at how climate change might affect the birds' breeding success.

If greenhouse gas emissions continue at the current pace, almost half of the breeding pairs on the Crozet and the Prince Edward Islands of Antarctica will decline within the coming decades as a consequence of "longer foraging trips and associated increase in energy expenditure."

"Marion and Prince Edward Islands, and Crozet island will have the biggest difficulty in the next 50 years, I would say. These are major population centers," Le Bohec told BBC News.

"But if we continue with the addition of greenhouse gases then Kerguelen, Falkland and Tierra del Fuego islands will also have difficulty."

The group of scientists has also studied a particular requirement of king penguin — second-largest of the 17 penguin species. These birds species prefer sub-antarctic islands, which are free of sea-ice and also have smooth sandy and pebble beaches to bring up their chicks.

"The problem is the pace of change. It is really very fast, and that will make it hard for the penguins to adapt," said Le Bohec.

"It is difficult to predict the outcome, but there will surely be losses on the way – if we are to save anything, proactive and efficient conservation efforts but above all coordinated global action against global warming should start now."

Speaking about the study, Dr Norman Ratcliffe (he is not directly involved in the research) from the British Antarctic Survey told BBC, "Long-term projections of the type presented here are always crude caricatures but I like this study because it does take a more mechanistic approach based on the known habitat requirements of the species rather than using a more traditional and simplistic thermal envelope model."

"For the time being, we know king penguin populations are still increasing across their range, probably due to them recovering from hunting pressure during the sealing era. So while it is possible that reduced accessibility of foraging habitat might cause loss of northern colonies in the future, there is no evidence that we have yet reached a tipping point at which this occurs," he said.