Satellite imagery has been used to estimate the population of an animal species for the first time, in a survey that discovered surprising new information about the emperor penguin population of Antarctica.

By counting penguins in images taken from space, scientists estimate the population of emperor penguins was around 595,000 in 2009 — roughly double previous estimates of between 270,000 and 350,000, reports a study led by the British Antarctic Survey.


Peter Fretwell talks to Quirks & Quarks on Saturday, April 21, at noon on CBC Radio One

That is valuable baseline information that will help scientists track how the birds are affected by climate change, Peter Fretwell, a geographic information scientist with the British Antarctic Survey, said in an interview with Quirks & Quarks that airs Saturday.

Emperor penguins, which stand as tall as a six-year-old child, breed and spend much of their lives on sea ice that is expected to melt significantly in coming decades.

"But it's very hard to predict how this will affect emperor penguin numbers if you don't have an idea of how many there are in the first place," Fretwell said.

Previously, it had been very difficult to get an accurate count of emperor penguins because the birds breed in such harsh, remote areas during the Antarctic winter, and it's hard for scientists to get there, Fretwell said.

The recent satellite count located four previously unknown colonies, and two or three others that had been thought to exist, but had never been located. The results show that colonies exist all the way around the Antarctic coastline, not just in certain areas where researchers had found previously known colonies.

Even though there are more penguins than previously believed, Fretwell thinks there is still reason to worry about them. Some scientists predict the population of emperor penguins will be halved in coming decades because of their reliance on the shrinking sea ice. Therefore, the fact that there are more to begin with "means we will actually lose more penguins," Fretwell said.

"But we will at least be left with a larger number at the end."

Sea ice extent is currently shrinking in some areas of Antarctica and growing in others. Climate models predict that overall, Antarctic sea ice will decrease 24 per cent in total extent by 2100, according to the Australian Antarctic Division.

Fretwell said the use of satellites to count penguins has only become possible in the past few years because of recent improvements in the resolution of satellite imagery, which can now distinguish objects on the ground just 50 centimetres apart.

Penguin colonies were identified in the images by the large brown stains of their feces on the white sea ice. The researchers zoomed in and were able to see black dots representing individual penguins or clusters of penguins, which were used to estimate the population.

The results were published earlier in April in the journal PLoS ONE.

Fretwell suggests the technique might soon be used to count other types of animals in a variety of ecosystems.


In satellite images, penguins were visible as black dots on the white sea ice. (DigitalGlobe)