The Evolution Of The Wet Tropics Of North Queensland

The Australian outback - with its vast expanses of flat land, dry grasses and kangaroos - is usually the image people have when they think about the world's largest island. But this was not always so. The Red Centre was once covered in broad-leafed forest between 20 million and 60 million years ago!

Australia was once part of a much larger land mass called Gondwana which included the modern continents of Africa, South America, Antarctica and India. Proof of this was provided when many of the same ancient plants and animals were unearthed in fossil beds some were discovered dispersed throughout parts of all these present day continents.

About 120 million years ago, Gondwana began to break up. Connections between Africa and South America were broken about 100 million years ago. About 80 million years ago, New Zealand and New Caledonia broke away from the eastern edge of the Australian plate. Finally, about 50 million years ago, Australia separated from Antarctica and began moving northwards. For 35 million years it was totally isolated from all other land masses until it collided with the Asian plate.

Although Australia contains less than one-thousandth of the world's tropical rainforests, these forests are some of the most signifricant ecosystems on earth. They are relics of vegetation types which were once much more widespread (fossil pollens indicating that most of Australia was covered by closed forests some 50 to 100 million years ago). The Wet Tropics now contains most of the world's plant relics of those ancient forests. All of Australia's unique marsupials and most of its other animals originated in rainforest ecosystems, of which the Wet Tropics is the closest surviving remnant.

The Wet Tropics provides a living record of the ecological and evolutionary process that shaped Australian plants and animals over the past 415 million years. The ongoing processes of speciation, extinction and adaptation have been determined by a complex history, particularly continental drift and cycles of climate change. These changes occurred slowly, allowing species to adapt, to change, and ultimately for speciation to occur.

Credits

Article "Evolution - From The Beginning" courtesy of the Wet Tropics Management Authority.