The world’s penguin population is in dramatic decline with more than a fifth of species facing extinction, according to research.

A study warns that the sharp reduction in penguin numbers is symptomatic of “catastrophic changes” occurring in the oceans caused by climate change, as well as damaging human activities such as commercial fishing and oil production.

The global penguin population has fallen by half since the beginning of the 20th century and now stands at 10m birds.

Of the 19 species that live at 43 different sites in the southern hemisphere, at least four are facing extinction. Experts believe that a further six species have experienced a decline in numbers.

The public’s fascination with the birds was recently revived by the Oscar-winning film March of the Penguins.

Narrated by Morgan Freeman, the American actor, it depicted the emperor penguins of Antarctica – one of the species in decline – as they leave their normal ocean habitat every autumn and walk inland to their ancestral breeding grounds to engage in courtship.

Conservationists are especially concerned about the future of yellow-eyed penguins and fiordland crested penguins – both native to New Zealand – whose populations have respectively dwindled to 1,500 and 3,000 pairs.

The numbers of Humboldt penguins, which are found in Chile and Peru, are also in steep decline, with only 12,000 pairs remaining.

Yesterday it emerged that scientists have developed technology allowing them to identify individual birds in a 20,000-strong colony of jackass penguins. They hope the camera software, which recognises spots on the bird’s chest, will help them understand why the population in South Africa is declining.

“Penguins are among those species that show us that we are making fundamental changes to our world,” said Dee Boersma, a professor of environmental science at the University of Washington, who has carried out the new research.

“The fate of all species is to go extinct, but there are some species that go extinct before their time and we are facing that possibility with some penguins.”

Her research reveals that the population of Magellanic penguins, found on the Atlantic coast of Argentina, has halved in less than 50 years. In the 1960s there were an estimated 400,000 pairs. Now there are only 200,000.

African penguins, native to South Africa and Namibia, have plummeted from 1.5m pairs a century ago to just 63,000 pairs today.

Boersma says that climate change is slowly killing Galapagos penguins in the south Pacific by changing the course of ocean currents which carry their fish supplies.

Their numbers have fallen to about 2,500 pairs – about a quarter of the size of their population in the 1970s when Boersma first studied them.

The report states that climate change is the principal cause of a 50% collapse in adélie and chinstrap penguin numbers in the Antarctic. When the ice melts, the chicks do not have sufficient fur or fat to survive in freezing water.

Boersma also blames an increase in commercial fishing and oil drilling and spills for destroying some penguin populations, particularly off the coast of Africa.

Not all penguin species, however, are on the decline. Phil Trathan, of the British Antarctic Survey, said: “In the Antarctic in the 1920s there were 700 pairs of king penguins – now there are 150,000.”

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