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The Trees of Antarctica

23 Sep

It is hard to picture Antarctica as anything other than the frozen wastes of today. The famous ice-shelves, frozen mountains, and hardscrabble climate seem fundamental to the very identity of the continent. But it was not always this inimical to life. In fact, sandstone deposits from Alexander Island and the South Shetland Islands reveal a diverse array of fossil life, from sea-dwelling molluscs, to plants, and even large vertebrates. In fact, evidence shows that millions of years ago vast forests may have covered the continent.

An antarctic forest would look somewhat like the forests of the Pacific Northwest United States or New Zealand. During the Cretaceous, eighty-foot tall pines, ferns, and mosses with gingkgoes and cycads would have dominated the ecosystem. But the forest life would have seemed strange to us – instead of deer and bears, the Antarctic forests were home to dinosaurs and their ilk, including the massive Glacialisaurus and the bizarre Cryolophosaurus.

Unfamiliar plants grew here too. Low-lying wetlands may have been home to the tree-like seed fern Glossopteris. From a distance a stand of Glossopteris might have looked like simply hundred-foot tall conifers, but standing underneath them the feeling would be much different. They grew claustrophobically close to one another – in some places there was little more than a body-length between each hundred-foot tall plant. Furthermore, if you listened as you walked, you’d realized there would be no familiar crunch of dried needles underneath your feet. There were no needles at all. Instead Glossopteris was covered in long tongue-shaped leaves that may have changed colors with the seasons.

An aside – Glossopteris has one final note to make in Antarctic history. Thirty-five pounds of Glossopteris fossils were found along the bodies of Robert Scott’s fatal Terra Nova expedition. They men were lost, frozen, and starving to death at the time and shedding supplies as they marched. The exact reason they decided to keep thirty-five pounds of rocks is unknown to me, speaks of a forlorn and desperate kind of hope.

Back to the trees – As time progressed, a new form of plant would have joined the conifers and ferns. The Cretaceous period also marks the development of flowering plants. Before then, no plant reproduced via flowers, but the new model proved successful and as flowering plants spread across the continents, beeches and other temperate trees would have joined the Antarctic ranks.

But life here was not always going to be kind to plants. Over the eons, the Antarctic landmass began to drift further and further south, forcibly changing the climate from temperate and tropical to the cold, dry polar climate we know today. Worse still, with the cold climate also came a shift in light patterns. Months-long summer days would have given way to equally long polar nights. Plants adapted as best they could, photosynthesizing constantly during the summer and becoming dormant in the winter. This system worked for a time, forests persisted until roughly 20 million years ago, but ultimately the harsh climate proved too much and Antarctica became the frozen wastes we know today.

Fossils are still being found in abundance here. Over 40,000 specimens have been unearthed so far, representing thousands of species. But with the exception of pranks, it’s unlikely anyone will ever see another tree south of the sixty-degree line any time soon.

Sources: Anarctica.ac.ukDiscovery.comWiki: Glossopteris

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Posted by on September 23, 2012 in Uncategorized

 

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