The Wet Tropics:
Daintree Rainforest and Kuranda SkyRail Rainforest Tour

View of Cape Tribulation through king ferns in the Daintree Rainforest.

This extraordinary World Heritage Site is filled with species which have been swept into the rainforest ecosystem over 100 million years of advance and retreat as climate changed.

In contrast to the Psionia forest on Heron Island, it is rare to find pure stands of plants.

For me, the image BELOW was as I imagined the place to have looked before humans were invented (about 3 million years ago). Australia offers many such timeless moments.

LEFT: Thornton Peak showing the clouds which provide moisture to the mountain retreat of the rainforest.

RIGHT: Cape Tribulation showing late afternoon clouds on the Queensland coast.

Biomass burning is a common environmental control method in Australia. In the North End, it is under the updrafts of the Intertropical Convergence Zone (ITCZ - RIGHT IMAGE) and contributes to the particles which reach the upper atmosphere. Particles in the upper atmosphere are candidates for mini platforms on which the chemical reactions of ozone depletion occur (under the influence of Asian emissions of CFCs).

In the lower atmosphere, particles form condensation nuclei for raindrops.

Click on the images to view at full size.

Three images ABOVE evoke ancient and modern problems facing survival of rainforest. Thornton Peak is seen in the background of intensive sugar cane agriculture. Climate and ancient, nutrient poor continental crust of the Australian piece of Gondwanaland make it tempting to plant cash crops on the limited suitable soils. Rainforest currently faces competition for these available habitats. Thornton Peak is thus a refuge for the unique ecosystem which is the modern Queensland Wet Tropics.

Fires from natural and human sources is also a risk to rainforest species. The risk of extinction increases as habitat for population clusers is restricted, making a species vulnerable to a single accident or incident.

But the rainforest is a fluid conglomeration of species. Over the last 100 million years (lucky proto-Australia was on the other side of the planet 65 my ago when the asteroid hit on what was to become the Yucatán Peninsula took out the dinosaurs), the forest has advanced and retreated, losing species to natural attrition and sweeping up new members with each retreat and advance from its montane stronghold.

Here is an approximate time line for events on the chunk of Gondwanaland which became Australia.

300 million years Before Present------club mosses and simple land plants (their descendents are still here!)
200 million years Before Present------dinosaurs invented
140 million years Before Present------Gondwanaland splits into proto-Australia with proto-Antarctica
120 million years Before Present------flowering plants like Idiospermum appear
100 million years Before Present------cycads and ferns still dominant
65 million years Before Present------The Big Hit and the Cretaceous-Tertiary (K-T) mass extinction
50 million years Before Present------Australia separates from Antarctica
15 million years Before Present------Australia dries out; rainforests retreat to mountains; migrations
across Wallace's Line on land bridges as sea level fluctuates; Papua-New
Guinea highlands form in collision between Australian and Asian plates

RIGHT: Click on the images to view at full size.

A flash digital image taken under the rainforest canopy shows how little sunlight gets to the forest floor in a rainforest. The species in the lower layers of the forest are adapted to perform photosynthesis in lower light intensities.

Slash and burn agriculturists take advantage of the fragility of this diverse ecosystem by girdling a few of the canopy species which are key species in the vertical structure of the forest. When these species die, the forest dies back in a cascade response or "domino effect" as bright sunlight damages shade-adapted species.

LEFT: Wherever there is a gap in the rainforest, plants grow on top of each other. Here you see a Philodendron (tree lover) climbing the lighted side of a canopy species.

RIGHT: This Idiospermum is one of the ancient canopy species. It is a species that is well over 20 million years old, which is the span of time David Raup and other statistical paleontologists have determined is the average time a species lasts on this planet. What is it doing right to beat the average? Its seeds are extremely toxic and were presumably dispersed by the giant wombat (marsupial, now extinct).

Australian plants and animals have a symbiosis where the nursing young absorb small amounts of native toxins from the mother's diet and become tolerant of the poisons later in life. The plant then gets a ride to another location in the gut of these animals, to be deposited in a dab of fertilizer in due course. Idiospermum now depends on humans to manage its dispersal in the Daintree.
The rainforest in contact with estuarine waters of the Daintree River.

LEFT: Cyclone damage.

RIGHT: Rhizophora mangroves at low tide showing the pneumatophore structures which allow oxygen to reach the roots buried in anoxic mud.

On 10 March 1996, 400 cm of rain (15.75 inches) fell on this ecosystem.
The relict population of the palm Licuala ramsayi.

This extraordinary species is adapted to cyclones like that of March 10. The circular pleated leaves fold in winds that shred and fell other plants. The trunks have so much silica to resist rotting in flood waters that they ring like glass when tapped!

ABOVE: The Licuala canopy showing the cyclone wind-adapted leaves.

LEFT: The Licuala understory showing the slender glassy trunks and young trees.

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