June 13, 2014
The Rise And Fall Of Prehistoric Penguin Populations, And What It Means To Modern Penguins
Gerard LeBlond for redOrbit.com - Your Universe Online
The penguin population from the last ice age to about 1,000 years ago has been on an up and down trend. However, due to a warming climate and retracting ice, certain penguin populations have steadily declined, according to a recent paper which was published in the journal Scientific Reports.
The team of scientists from the Universities of Southampton and Oxford used a genetic technique to estimate penguin populations of the past. Before human interaction influenced the climate about 30,000 years ago, Antarctica gradually warmed and three species of penguin - Chinstrap, Adelie and southern Gentoo penguins - actually saw an increase in their populations. During the same period, the Falkland Island Gentoo penguin population remained stable.
Also involved on the project were scientists from the British Antarctic Survey, US scientists from Oceanites Inc, Woods Hole Oceanographic Institution, and the University of North Carolina, Wilmington.
“Whereas we typically think of penguins as relying on ice, this research shows that during the last ice age there was probably too much ice around Antarctica to support the large populations we see today. The penguins we studied need ice-free ground to breed on and they need to be able to access the ocean to feed. The extensive ice-sheets and sea ice around Antarctica would have made it inhospitable for them. What is particularly interesting is that after the ice age, all of these penguin populations were climate change 'winners', that is to say the warming climate allowed them to expand and increase in number. However, this is not the pattern we're seeing today. Adélie and Chinstrap penguins appear to be declining due to climate change around the Antarctic Peninsula, so they've become 'losers'. Only the Gentoo penguin has continued to be a 'winner' and is expanding its range southward,” explained study author Gemma Clucas of the University of Southampton in a recent statement.
Co-author of the paper Tom Hart from the Department of Zoology at the University of Oxford added, “We are not saying that today's warming climate is good for penguins, in fact the current decline of some penguin species suggests that the warming climate has gone too far for most penguins. What we have found is that over the last 30,000 years different penguin species have responded very differently to a gradually warming world, not something we might expect given the damage current rapid warming seems to be doing to penguins' prospects.”
The study consisted of collecting feathers and blood samples from 537 penguins from different colonies in the Antarctic Peninsula. The scientists sequenced a region of DNA that evolves quickly. By using the mutation rate as a calibration point, they were able to estimate the penguins genetic diversity. The team charted how population sizes differentiated over time by analyzing the data collected.
“During the last ice age Antarctica was encircled by 100 percent more winter sea ice than today. As ice retreated, these penguins had access to more breeding sites and more open ocean to feed,” Hart stated.
“Despite historic warming clearly opening up new opportunities for penguins, we should not assume that current rapid warming caused by human activity is good for penguins as a whole. Evidence from other studies shows that climate change today is creating lots of losers and few winners – with chinstrap and Adélie populations around the Antarctic Peninsula declining fast. This is probably as a result of reductions in sea ice causing stocks of the krill they feed on to shrink, whilst populations of Gentoo penguins, which don't rely on krill as much, grow and expand,” Clucas concluded.