Past studies have suggested penguins actually thrive when the climate is relatively warm, since cold climates increase sea-ice extent, which makes it difficult for the birds to access their beach colonies and food-rich waters.
    
Researchers Liguang Sun and Zhouqing Xie, from the University of Science and Technology of China, analyzed how the populations of Adelie penguins changed over the past 700 years in the Ross Sea, a region in Antarctica that is at a higher latitude than previous study sites.
    
They analyzed sediment samples from multiple depths for cholesterol and cholestanol, which are bio-markers indicating soil contamination by animal feces, 'LiveScience' reported.
    
On the basis of variation in the markers, researchers divided up the timeline into four time periods. The bio-markers suggested penguin populations boomed during Period II (1490 to 1670), declined significantly during Period III (1670 to1950) and increased steadily since then in Period IV (1950 to present).
    
The amounts of vegetation corroborated the penguin data. Antarctic algae require a lot of nutrients from penguin droppings to thrive, whereas penguin trampling endangers lichens, the report said.
    
The evidence shows that algae abundances increased and decreased along with the penguin populations, but lichen abundances showed the opposite trend.
    
The summer temperatures during the Little Ice Age were about 2 degrees Celsius colder than the previous 200 years — this chilly climate promoted more sea-ice extent, which would normally be detrimental to penguins.

(Agencies)

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