While Australia was still close to Antarctica the continent was dominated by rainforest and the eucalypt forests grew only in those places that were drier and less fertile. As the continent drifted further north away from the rain-laden winds of the Southern Ocean and approached southern Asia dry conditions prevailed and around 13 million years ago the centre of the continent began to dry out. Many rainforest plants and animals adapted to the slowly drying landscape and finding conditions more to their requirements, the eucalypt forest expanded. With a more open canopy allowing sunlight to reach the ground the grasses also expanded their range. Taking advantage of vast quantities of low nutrient grasses the kangaroos, wombats and other terrestrial animals increased in numbers and in size until Australia was dominated by the mega-fauna.
The fortunes of these incredibly ancient forests and their animals have depended on the climate. Over millions of years the climate oscillated between ice ages where rainfall declined, and eucalypt forests expanded and interglacials, where rainfalls increased, and rainforests reclaimed parts of their former range. Over an unimaginable period of time the rainforests and eucalypt forests evolved to compete against one another. They have fought one another for domination of the Australian landscape. In the battle the giant strangler figs are the soldiers of the rainforest. Advancing from the edge of the rainforests, the strangler fig conquers new territory by growing on top of and eventually strangling eucalypt and other trees. It then casts out its wide canopy to shade the ground and provide the perfect habitat for more rainforest plants.
To triumph over rainforest territory, the eucalypts have evolved to become some of the worlds most advanced trees. Flooded Gums, Blackbutts and Red Gums can defend themselves from strangling figs by shedding their bark every year thus removing any young figs attached to them. Eucalypt trees also have leaves full of flammable eucalyptus oil that burns fiercely. By encouraging fires to burn the eucalypt forest provides sunlight and nutrient-rich ash for their seedlings. As the rainforest seedlings prefer to grow in shady soils its territory can be lost to fire. To combat this,rainforest plants have leaves that are fire retardant.
It has taken millions of years for the rainforest to concede territory to the aggressive eucalypt forest, aided by a drying out of the continent. Because rainforest grew in those localities that had the most consistent rainfall and on the most fertile soil, the arrival of European people in Australia was a disaster for the rainforests of Byron Bay and north-eastern New South Wales, 99.7% of which was cleared for agriculture and was logged almost into extinction. Clearly, the battle now is for the survival of the Australian subtropical rainforests.
