Antarctic penguins have benefitted from climate warming in the past, but the balance is now tipping too far in the other direction for some penguins, a study published in Scientific Reports this week suggests. The study compares the historical responses and more recent trends in response to climate change in Antarctic penguins to distinguish between the impacts of natural variation and climate change linked to human activity.

Climate change poses a threat to biodiversity and can produce ‘winners’ (species that benefit from the change) and ‘losers’ (species that decline or become extinct). Gemma Clucas and colleagues used DNA sequencing techniques to assess the historic demographics and population structure of three species of Pygoscelis penguin (Gentoo, chinstrap and Adelie), presenting evidence that all three species responded positively to climate warming after the Last Glacial Maximum (LGM) by expanding their population range. However, more recent trends suggest that while the more generalist Gentoo penguins appear to be benefiting from the current climate change, expanding their range and population size, Adelie and chinstrap penguins seem to be suffering a ‘reversal of fortunes’ and are declining in the Antarctic peninsula, the opposite response to that shown after the LGM.

One potential reason for the reversal of fortunes shown by Adelie and chinstrap penguins is their dependence on the declining Antarctic krill as a food source, whereas Gentoo penguins have a more diverse diet making them less sensitive to the decline in krill. The authors postulate that this may show that the added effects of anthropogenic influences, outside the normal range of past climate variation, may alter past population responses.