Rugged Falklands landscapes were once lush rainforest, researchers say

A researcher from the University of Southampton in the UK has discovered evidence that the rugged, treeless landscape of the Falkland Islands was home to a lush and diverse rainforest 30 million years ago.

A study led by Dr Zoë Thomas, who led an international team of scientists, reveals that the South Atlantic archipelago was once covered in cool, humid forests, similar to the current rainforests found in Tierra del Fuego, off the tip of South America.

The detailed results of the research are recently published in the journal Antarctic Sciences.

The scientists conducted the research after getting clues about the location of the buried remains of the ancient forest through word of mouth in the tight-knit community of Port Stanley, the capital of the Falklands. Chance conversations led them to find perfectly preserved prehistoric tree remains and pollen at a construction site in early 2020.

“We were in the Falklands doing research for another project when a fellow researcher based on the island mentioned that a friend had told him something interesting had been dug up by a builder he knew,” says Dr Thomas, a physical geography expert at the University of Southampton.

She continued: “Excavators at the site of a new retirement home in Stanley dug through a deep layer of peat which was filled with large tree trunks and branches. These were so well preserved they looked as if they had been buried the day before, but they were in fact extremely old.

“Our interest was immediately piqued, as finding tree remains here was puzzling. For at least thousands, if not millions, of years, the Falkland Islands have not been able to support trees. It is too windy and the soil is too acidic. This raised the intriguing question of exactly how old the wood in this forest is.”

With the help of members of the South Atlantic Environmental Research Institute (SAERI) in Port Stanley, samples of the peat layers and deposits were collected from the Tussac House site near Stanley Harbour. These were carefully transported to Australia for laboratory testing at the University of New South Wales, where the sediments were meticulously sampled and the wood analysed using specialised scanning electron microscopes.

The tree remains proved too old to obtain conclusive results from radiocarbon dating, so pollen spores were used instead. The scientists analyzed a variety of spores compacted and sealed in the same layers of peat as the wood. The pollen records allowed them to conclude that the tree’s trunks and branches were between 15 and 30 million years old.

The Falkland Islands are a British territory located 13,000 kilometres from the United Kingdom in the South Atlantic. Consisting of two main islands and 778 smaller islands, they cover an area just over half the size of Wales and are known for being wet, cold and windswept, with rapidly changing weather conditions. Their landscape is not dissimilar to that of Dartmoor in the United Kingdom.

Tens of millions of years ago, the climate of the South Atlantic was much warmer and wetter than today, and supported a tropical forest. This was cooler than the tropical forests we are generally familiar with, such as the Amazon rainforest, but it still supported a rich and diverse ecosystem of plants and animals.

Many of the tree species growing in the Falklands at the time of Tussac House’s sampling are now extinct, but they are thought to have been sown to the islands by being carried by the prevailing westerly winds from the rainforests that covered much of the southern hemisphere, including what is now mainland South America.

Scientists cannot be sure what led to the disappearance of the islands’ rainforest and its transformation into peatlands, but it is reasonable to assume that it is due to climate change and a shift to colder, drier conditions.

Dr Thomas comments: “It’s incredible to think that if we hadn’t had the chance to talk and interact with the people of such a close-knit community at that particular time, we might never have recovered these perfectly preserved tree samples. Until our visit and the discovery of the construction worker, no one had any idea that six metres below their feet were perfectly preserved relics of an ancient rainforest and exquisite fossilised pollen. I am very grateful to the islanders who, through their welcome and openness, have given us this unique opportunity to investigate.”

Looking to the future, Dr Thomas believes it is unlikely that the islands will return to a forested landscape in the near future: “Current projections suggest that the region will become warmer, but also drier, raising concerns about the risk of erosion of peatlands, which are sensitive to climate change.”