During the Cretaceous period (145-65 million years ago) flowering plants evolved in the region of modern day South America and Africa, and continued to spread across the globe, dominating vegetation systems. The period was ended by a mass extinction event believed to have been caused by a meteorite striking earth and killing 75% of all species. Those that survived included inhabitants of the lower southerly latitudes of Gondwana, including present day Australia.
The vegetation began to recover and by 50 million years ago, much of the Australian continent was covered in rainforests supported by a climate wetter then we experience today. However, Australia, now broken away from Gondwana, proceeded into the drier and warmer north and by 38 million years ago, temperatures had increased. Consequently, the rainforest covering Australia was pushed back leaving small pockets of refugia preserved along the moister east coast of Australia. Today, these pockets maintain some of the primitive rainforest species that existed during the Cretaceous period. As such, rainforests in Australia are now a mix of these original species, as well as their modern-day relatives. Further new additions have been made including those of Indo-Malaysian origin, particularly in our northern rainforests1, 2,3
All Australian marsupials have their origins in the rainforest4
Although we often consider that the remnant ‘archipelagos’ of rainforest along the east coast of Australia are a consequence of human activity, this is not necessarily the case. Instead, this naturally occurring situation, evident for the past 50 000 years, resulted from a number of factors such as succession of rainforest vegetation by other sclerophyllous vegetation. Additionally, climatic drying concurrent with volcanic activity helped to shape the landscape thus leading to an array of unique habitats. Consequently, diversification has continued within each pocket resulting in hundreds of unique species, many of which occur in a limited number of locations2, 3
The consequence of this timeline is that Australian rainforests today have species with origins dating back to the early vascular plants, and others which have evolved more recently. The rainforests of Australia, amongst the oldest in the world, are highly significant globally as they tell this story of the evolution of plants from the super continent Pangea to modern times. This includes some of the world’s oldest ferns, gymnosperms and angiosperms. Further importance lies in the highly localised nature of many species including numerous examples of rare and threatened plants and animals, few of which are actually common. The Tasmanian Wilderness World Heritage Area, for example, contains strong populations of numerous species which are rare or extinct on the mainland. Every remnant of rainforest in Australia today is therefore diverse, unique and highly valuable2, 3, 5
It is of vital importance for the future that the broadest possible genetic base of all species be conserved so that future evolutionary potential is maintained6.
Besides the natural beauty of Australian Rainforests, they also have strong cultural values for Aboriginal groups, such as those in the Wet Tropics (Queensland) where Aboriginals have lived within the rainforest for thousands of years and continue to do so today. The rainforest landscape holds strong spiritual and cultural connection for Aboriginal people which is evident in Dreamtime stories founded within the region7