This rapid warming has enormous implications for ecosystem functioning and various geomorphological processes that affect land surfaces – both on Marion Island and its surrounds and as a harbinger of the impacts climate change could have in southern Africa.

“Much of the research and insights we can garner from Marion Island we can use to hypothesise what will happen in southern Africa, giving us a regional perspective of climate change in the southern hemisphere,” says Hedding, who visits the island for six weeks every year and works with scientists from other South African universities, the British Antarctic Survey, the Norwegian Polar Institute and the French Polar Institute, among others.

A simple ecosystem is now under siege

One factor that makes Marion Island ideal as a site for climate change research is its relatively simple ecosystem, consisting mainly of grasses and shrubs, birdlife, and marine mammals. This simplicity makes it easy to monitor changes from climate shifts.

“There are very specialised species on the island, specifically adapted to survive there. If you change the parameters, those native species struggle, whereas invasive species have the plasticity to capitalise on and accommodate changes.”

Marion Island contains approximately 40% of the world’s wandering albatross population. These birds are now under huge pressure from the island’s most prolific and rapacious invasive species, mice.

“Mice typically eat a lot of invertebrates and vegetation. When food is scarce, and they are under stress, they start attacking and eating albatross chicks and adults. Those species are long-lived and endangered, and mice could have a profound impact on their ability to survive,” Hedding says.

“The island is far drier than it has been in the past, causing vegetation dieback, which is essentially exhibiting drought conditions. When you combine heat stress with drought conditions, it does not bode very well for the ecosystems that traditionally function in a very cold, wet environment.”

Specks of land in a vast ocean

Apart from its simple ecosystem, other reasons that make Marion Island so singular as a climate change research site are its geographic location in the mid-latitudes of the southern hemisphere, where there is much more ocean than land.

“If you think of a world map, you have several continents in the southern hemisphere, and then you have a big gap with Antarctica in the south. Because there is so little land in the Southern Ocean, Marion Island provides us a platform from which to assess climate change in this ocean,” Hedding says.

“And because the island is a meeting point of ocean currents that distribute heat across the globe, you can readily see how shifts in ocean currents and climate can impact an island and then use those insights to see how climate change may impact southern Africa.”

The connection between the changes on an increasingly warm and drying Marion Island and the frequency and intensity of extreme weather events in Southern Africa is becoming more apparent, from flooding in Limpopo and Mpumalanga to the current drought in the Knysna area.

Behaviour change can make a difference

Based on scientific evidence across disciplines ranging from geomorphology and oceanography to palaeontology and marine biology, there is consensus among the scientific community that anthropogenic forcing – that is, human activity – is the main cause of ocean and atmospheric warming and associated landscape changes.

Hedding says consumers should not discount the impact – positive or negative – of their own behaviour.

“It all comes down to personal choice from a sustainability point of view. People underestimate the impact an individual can have by, for instance, installing solar or a solar geyser to reduce their reliance on coal-fired power, driving a hybrid car, growing their own vegetables, and avoiding plastic bags. These actions add up over your lifetime and can have a beneficial impact on the environment.”

Fire and ice – the uniqueness of Marion Island research

• In examining how landscapes on Marion Island respond to climate change, Prof David Hedding focuses not only on contemporary changes over the last 50 to 70 years. Much of his research dates back 60 000 years, when much of the island was covered in ice. “We extract rock samples and build paleoclimatic reconstructions to work out where, when and how quickly the glaciers retreated and what the landscape looked like 20 000 to 30 000 years ago,” he says.
• Marion Island is a volcanic island, quite close to a plate boundary, offering terrestrial scientists like Hedding the opportunity to explore how lava flows and mantle dynamics shaped the island. The last volcanic activity on the island was in 1980.
• Marion Island is a South African island that, along with Prince Edward Island, was annexed from the United Kingdom in the late 1940s. This was not a hostile annexation, but one carried out by agreement between the two governments, which were concerned about the possibility of a German occupation of Marion

* By Clairwyn Rapley, Directorate Research Support