Imagine the view from South Africa’s west coast during the Last Glacial Maximum (LGM) more than 20,000 years ago: In the distance you can see at least 15 major islands, the largest of which, with an area of ​​300 square kilometers, filled with hundreds of millions. seabird and penguin colonies. Now imagine that between 15,000 and 7,000 years ago the sea level rose a hundred meters and gradually covered these large islands, until only small hills and ledges remained above the water. Over the last 22,000 years, this has caused suitable nesting habitats for African penguins to decline tenfold and their populations to decline.

This is a paleo-historical picture of the geographic range of African penguins, created by scientists from the Evolutionary Genomics Research Group in the Department of Botany and Zoology and from the School of Climate Studies at Stellenbosch University (SU). They hope the effort will provide new insight into the current vulnerability of Africa’s last remaining penguin species.

The study, titled “Natural late-Pleistocene decline in African penguin populations increases risk of anthropogenic extinction,” was published in Africa. marine science journal April 20, 2023. First author of the paper and PhD candidate in the university’s School of Climate Studies, Dr. Heath Beckett says this paleo-historical image of several million is in stark contrast to the current reality of post-1900 declines in African penguin populations.

In 1910, Dassen Island (an island off the west coast, an area of ​​about three square kilometers) was populated with approximately 1.45 million penguins. However, in 2011 the entire population of African penguins in South Africa fell to 21,000 breeding pairs, down to just 13,600 in 2019. About 97% of the current penguin population in South Africa lives in just seven breeding colonies. In May 2005, the International Union for Conservation of Nature classified African penguins as endangered.

Paleo-historical estimates of penguin population size

So what were the south and west coasts of South Africa like during the last ice age? And what can this tell us about the size of the penguin population?

Because penguins prefer to breed on islands to avoid predators from the mainland, the researchers used topographic maps of the ocean floor off the coast of South Africa to identify potential historic islands that lie between 10 and 130 meters below current sea level. To qualify as penguin-friendly, the islands had to be protected from terrestrial predators and surrounded by foraging areas suitable for sardines and anchovies within a radius of 20 kilometers.

Assuming sea levels were significantly lower during the last ice age, the researchers identified 15 large islands off the west coast; largest island 300 km² It is located 130 meters below the sea surface. Then, taking into account sea level rise over the past 15,000 to 7,000 years, they identified 220 islands that would provide nesting conditions for penguins. Of the 216 islands, the area is less than one square kilometer, some as small as 30 m.²little more than a rock.

Today, the five largest islands off the west coast of South Africa are Robben Island (~5 km²), Dassen Island (~3 km²), Property Island (~1.8 km²) and Seal Island and Penguin Island (both under 1 km)²). Possession, Seal, and Penguin Island are located off the coast of Namibia.

The researchers calculated penguin population estimates based on the current area of ​​the island, assuming that penguins typically nest no more than 500 meters from the shore, based on initial available population density estimates.

Following this approach, they estimate that between 6.4 million and 18.8 million people may have lived in southern Cape waters during the Last Glacial Maximum. However, due to sea level rise between 15,000 and 7,000 years ago, African penguins’ nesting habitat was greatly reduced.

According to Dr Beckett, the main aim of the study is to show that there has been a significant change in habitat availability over the past 22,000 years. “It could have had a huge impact on penguin populations. These populations are now under additional human pressure in the form of climate change, habitat destruction and competition for food,” he explains.