The Gondwana connection 2012 A living museum....... World Heritage Protected Australian rainforests have long been continents which gradually drifted Welcome to ‘Tropical Topics’, a considered poor cousins of rainforests apart. Australia was the last continent newsletter designed to help you in other parts of the world. to break away, about 45 million years keep up to date with natural ago. science and conservation news The ‘jungles’ of Africa, Asia and and issues of north Queensland.This South America conjure up romantic For 30 million years Australia’s life innovative monthly newsletter will visions of exotic paradise and ‘Tarzan’ evolved in isolation. As the climate provide you with interesting reef and movies. So much so that we are became drier many species died. rainforest facts. constantly trying to emulate them by Others adapted to the drier conditions What’s so special about the Wet landscaping our gardens and resorts and survived to colonise the vast Tropics? with introduced foliage. (Which in areas of dry open forests, grasslands To be selected for World Heritage many cases has resulted in the and deserts which cover much of the listing, an area must satisfy at invasion of our native forests by continent today. Only the least one of the following criteria. ‘runaway’ exotics.) mountainous regions of the east coast It must represent: remained constantly moist. It is here • a major evolutionary stage of What respect we have held for our that the last remaining refuges of the earth; native flora in the past has generally Australia’s ancient tropical rainforests • a continuing process of been reserved for the distinctly survive, with many species little geology, evolution, or man and- Australian flora of the drier parts of changed since the evolution of the environment; the continent; our famous wattles, first flowering plants. • superlative natural beauty; or eucalypts, banksias and grevilleas. • a habitat that shelters threatened Most scientists believe that these plants and animals. plants all originated from the ancient stock of Gondwana, the living The Wet Tropics satisfies all four! descendants of which can be found in the Wet Tropics. This month ‘Tropical Topics’ will provide an insight into how the Wet Tropics represents a major Gondwana - a supercontinent which evolutionary stage of the earth, existed hundreds of millions of years and why it could have gained ago - comprised the southern World Heritage listing on this continents as well as India and parts basis alone! of southern Asia. (The northern continents were joined in a similar landmass called Laurasia.) Some plants such as the idiospermum from Cape For millions of years life evolved Tribulation did not evolve. They appear today much as they did across these supercontinents. millions of years ago. Dinosaurs came and went and More primitive flowering flowering plants developed. At plants are found in the Wet Tropics than anywhere else times much of the land (including on earth. what is now Australia) was covered by rainforest. About 180 million years ago Gondwana started to break into Wet Tropics rocks What have rocks got to do with the rainforest? Everything! Rocks are the foundations and have the texture of porcelain of the landscape and the origin of the • Granites formed from the injection formed in the southern and western soil. They even affect the weather. For of magma (molten rock) into overlying parts of the Wet Tropics about 250 example, the north-south alignment of rocks about 200 to 300 million years million years ago. More recently (about coastal mountains of north Queensland’s ago. Magma is rich in quartz and one to three million years ago) basalt Wet Tropics traps rain-laden clouds from cools slowly, deep below the surface, lava, which contains no quartz, erupted the moist ocean breezes. In normal years forming coarsely crystalline, lightgrey and flowed over the Atherton rain erodes the rocks at an imperceptible to pink rock which is only Tableland and other parts of the Wet rate creating the lofty crags, ridges, exposed where overlying rock has Tropics. The basalt, often containing valleys, gorges and spectacular eroded. bubbles, formed a layer of black, finely waterfalls which form the dramatic crystalline rock which weathered to landscape. Rock fragments removed • Volcanics formed when lava erupted bright red soils. in this sculpting process accumulate onto the surface of the land and cooled on lower slopes to form a variety of quickly. Some light-pink and grey soils which in turn support a range of volcanic rocks which are rich in quartz forest types. Rocks weather differently. Grain size and mineral composition of rock 1. Sediments accumulate determine how fast it erodes, the on the bottom of an ancient depth of the soil it produces, its ocean extending west of texture and nutrient content. Soils in today’s shoreline. the Wet Tropics vary from thin, stoney, leached and infertile ‘lithosols’ of some ridge-tops to the deep, red, rich and fertile basalt derived soils of the Atherton Tableland. 2. Crustal movements compress the sediments, The large-scale structure of the rocks, folding and melting them into along with their variable resistance to metamorphic rocks. weathering provides the landscape master plan. Cracks and fractures in the rock can form lines of weakness that stretch for kilometres, often directing the flow of creeks. Rocks without cracks are most resistant to 3. Molten granite magma erosion and may be left as pinnacles is injected into the when surrounding rocks are eroded. metamorphics and solidifies slowly. Three main types of rock form the Wet Tropics landscape; metamorphics, granites and volcanics. Each type has its own characteristic combination of chemical and structural properties: 4. Millions of years of erosion removes the rock overlying • Metamorphics were formed about the granite . Granite is more 360 million years ago when sediments resistant to weathering on the bottom of an ancient ocean and remains proud of the were compressed by movements in landscape to form the highest the earth’s crust. The sediments fused mountains (eg. Bellenden Ker, into a layered and folded block of Bartle Frere and Thornton mixed composition extending for Peak). hundreds of kilometres along the coast and for a hundred kilometres inland. Folds and layers give rise to 5. Basalt lava erupts from characteristic weathering patterns volcanoes to flow over the such as those found in shale and Atherton Tableland and other slate. places. Tropical Topics 2012 “The cat’s caught a rat!” Facts and stats What’s so special about that? believed to have migrated to Australia on Wet Tropics WHA Plenty when the rat turns out to be a from Papua-New Guinea thousands of prehensile-tailed rat. As its name years ago when there was a land bridge Having been around for more then 100 suggests, this rare nocturnal rat has a across Torres Strait. million years, rainforests of the Wet tail which it curls upwards to grip Tropcis World Heritage Area are the twigs when climbing. It can even hang Little is known about the habits and oldest, continuously surviving rainforest by its tail. distribution of this beautiful, little rat. on earth. Sadly, domestic cats have been The prehensile-tailed rat (along with responsible for most of the finds. The Conifers and cycads of the Wet Tropics are living remnants from the times, the cuscus and tree kangaroos) is first one discovered in Australia was 200 million years ago, when dinosaurs brought into the lodge at Lake Barrine roamed the earth. by a cat in 1974. Since then, several have been caught in Kuranda, also by cats. Two have been collected from Gordon Creek, near Iron Range and an owl pellet from Mt Lewis contained the remains of one. A prehensile-tailed rat nibbles on the fruit of a pandanus. The World Heritage Area covers nearly 900 000ha, extending more than 400km between Cooktown and Townsville. It covers only 0.1% of Australia’s total land mass but has: • 40% of Australia’s bird species • 30% of Australia’s mammal species • 60% of Australia’s butterfly species • 21% of Australia’s reptile species • 21% of Australia’s cycad species • 29% of Australia’s frog species • 65% of Australia’s fern species • 30% of Australia’s orchid species About 300 000 people live in or within 50km of the Wet Tropics World Heritage Area. Want to know more about the evolution of the plants and animals of the Wet Tropics? contact the WTMA office on 40520533 to grab an A1 The Wet Tropics currently receives about size Evolution poster, part of the animals of the Wet Tropics series. 2.5 million visits per year. Tropical Topics 2012 The Gondwana connection With a family tree dating back at least 20 million years, musky ratkangaroos are considered the most primitive of living kangaroos. Four million years ago, their west Victorian relatives died out, leaving them as the sole survivors of the genus Hypsiprimnodon. The land masses of the world were once joined into a super-continent called Pangaea. This separated into two smaller land masses, Laurasia in the north and Gondwana in the south. Australia was part of Gondwana. Until recently, north Australian rainforests were thought to have invaded from Asia when the continental plates collided. More recent theories suggest that Australian rainforests are largely inherited from the ancient stock of Gondwana. This is particularly true of upland and southern forests, while lowland forests have mixed Asian and Gondwanic origins with refugial areas, such as Noah Creek in the Daintree, where Gondwanic plants predominate. 180 million years ago Gondwana started to break into continents which gradually drifted apart. Australia broke away about 45 million years ago. Compare the skull of a modern platypus (left) with the 15 to 20-millionyear- old fossilised skull (right) of a platypus ancestor found at Riversleigh Station, north-west Queensland.