The myth of the world's oldest culture
The lost world of the Bradshaws
Why no cities or villages?
The extinction of the Megafauna
Migrantion of flora and fauna
Wrestling and reconciliation
The Retreat of Australian Rainforests
Dating back more than 100 million years, Australia has pockets of rainforests that are more than 10 times older than the Amazon. These pockets still contain ferns, conifers and angiosperms that once covered the Gondwana super continent.
How long rainforests continued to cover most of Australia after the break up of Gondwana is a subject of debate. In 2002, the discovery tree kangaroo remains in caves of Nullarbor Plain (now a desert) indicated that many of the rainforests lasted up the Middle Pleistocene (781 to 126 thousand years ago.)
The Nullarbor plain is now mostly desert, but when humans first arrived in Australia it was perhaps covered in forest and was home to tree-kangaroos.
Just as there is debate when the rainforests retreated, there is debate about the cause. Some scientists propose that much of the retreat was caused by burning of the rainforest by humans around 60,000 years ago. According to the theories, burning the forest had two major impacts. Firstly, the composition of the ecosystem changed as plants that could survive fire, or quickly recover from it, had significant advantages of plants that could not. Over tens of thousands of years, these plants evolved to encourage fire, not because they needed it, but because fire allowed them to outcompete other plants. (Fire harms all plants.) As these plants became more dominant, fires caused by lightening strike became more common in the ecosystem. Fire sensitive species were largely wiped out. In the Kimberley, remnant rainforest clung on in gorges and shelters that protected them from fire and can still be experienced today. Outside of these shelters, some fire resistant trees hung in sparse woodland or was in turn surpassed by grass.
The second major impact of the bushfires was to dramatically decrease the amount of rain falling over Australia. Instead of condensation in central Australia resulting in low pressure systems pulling air inland from the oceans, central Australia became dominated by high pressure systems that pulled hot air from deserts over the forested regions. Furthermore, with fewer forests trapping water when it fell, the rain that did fall sunk into the sands or evaporated. As a consequence, water recycling largely stopped. In a rainforest, up to 50% of rain that falls will be sucked up by trees, be transpired and fall again on forest as rain. The more than the rainforests retreated, the less water recycling that occurred. A tipping point occurred 40,000 years ago when the annual monsoon over central Australia failed; resulting in most of the rainforests being lost forever.
In Purnululu National Park, sandstone domes have provided some protection from fire, thus allowing rainforest to hold on where shrub and fire prone woodland has taken over elsewhere.
When Europeans arrived, they set about finishing off much of the little rainforest remained. In the last 200 years, three-quarters of the surviving rainforests have been cleared. Some of the rainforest has been cleared to make way for agriculture, while other pockets have been logged to access the prized timbers such as Red Cedar, Rose Mahogany and Coachwood. Ironically, the desire to continue to access such timbers gave rise to demands to preserve the rainforests as early as the 19th century. Basically, loggers and furniture makers were concerned about rainforests being cut down to make way for agriculture and the associated repercussions for their industry.
Cold climates are not often associated with rainforest, but the temperate rainforests of the Tarkine in Tasmania shows that the two are not mutually exclusive.
The Daintree Rainforest has existed continuously for more than 110 million years, making it possibly the oldest existing rainforest in the world.
|"They look ancient but at 10,000 years of age they’re much younger than the lightly built Mungo people. How could that be?
"The Bradshaw Paintings are incredibly sophisticated, yet they are not recent creations but originate from an unknown past period which some suggest could have been 50,000 years ago." Bradshaws
"The reduction of plant diversity, however it came about, would have led to the extinction of specialized herbivores and indirectly to the extinction of their non-human predators." Megafauna extinction
" Is the keelback’s ability to coexist
with toads a function of its ancestral Asian origins, or a consequence of rapid adaptation since cane toads arrived in Australia?" Migrant flora and fauna
"I've set myself the modest task of trying to explain the broad pattern of human history, on all the continents, for the last 13,000 years. Why did history take such different evolutionary courses for peoples of different continents? (Jared Diamond)" Why didn't Aborigines build cities?
"It then dawned on the old man lizard that the lesson to be learnt by watching the kangaroos, was that death need not be the outcome of the fight." Wrestling and reconciliation