| ECOLOGICAL WONDERS | Gondwana Link Home |
Australia is one of the biologically richest parts of the world. It has been recognised by the United Nations as one of twelve "mega-diverse" nations in the world and has more than twice the number of endemic species as other mega-diverse nations. 82% of our mammals, 45% of our terrestrial birds, 85% of the flowering plants, 89% of the reptiles and 93% of the frogs are found nowhere else in the world. They include some of the weirdest plants and animals imaginable, that have evolved over immense periods of time to flourish amongst the vagaries of our climate and our complex array of infertile soils.
Much of this biological richness is concentrated in south-western Australia, one of the world’s 34 ‘biodiversity hotspots for conservation priorities’. Though only covering 5% of the Australian land mass, this area has an estimated 8,000 plant species - more than one-third of Australia’s known flowering plants. Of these, 75% of the plants discovered so far are endemic to the south-west and around 20% are yet to be scientifically described. Plant diversity is concentrated in complex patterns, with rapid turnover across the landscape. Areas of similar soil and slope as little as half a kilometre apart may have less than 50% of their species in common.
The booklet "Reasons for Richness - The Nature of the Fitzgerald Biosphere Flora", written by Nathan McQuoid, Greening Australia, is an introduction to the reasons behind the botanical richness of the Fitzgerald Biosphere. This illustrated guide is well worth reading. Click here to view "Reasons for Richness" on the screen (400kb pdf). For printable version (3.8Mb pdf) click printable version.
We still know very little about this wonderland which sits at the forefront of biological exploration. As but one example, the number of plant species known to occur in the Fitzgerald River National Park has increased by 300% in the last 25 years, and now totals more than all the plant species in all Australian rainforests combined.
To flourish in the south-west's semi-arid and nutrient starved landscape, these plants have developed an amazing array of mechanisms. Many eucalypts grow as mallees, which are effectively trees with the trunk kept underground, safe from fire. The upper branches of these mallees are structured so as to harvest the sparse rainfall and deliver it directly to the root system, which often penetrates into the ground more than ten times the height of the above ground section.
Some plants gain nutrients from trapping insects while others, like the orange flowered Christmas Tree (Nuytsia floribunda) and the aromatic Sandalwood (Santalum spicatum), send out long roots to parasitise its neighbours. Tiny Laxmannia’s, barely taller than your toes, perch themselves above the hot sandplain on tiny stilt roots, looking for all the world like a miniature mangrove forest.
And the fauna is no less spectacular. There are frogs that live underground and mallefowl that build compost heaps to incubate their eggs. The tiny honey possum, Tarsipes rostratus, is just a tad larger than your thumb, has a jawbone adapted for feeding entirely on pollen and nectar, and the males have the largest testicles per body mass of any of the world's mammals (and enviable sexual endurance).
The evolutionary pressures are so intense in the south-west you can actually feel them happening around you. Drive, or preferably walk, fifty kilometres across the Fitzgerald River National Park and watch Grevillea macrostylis slowly morph into Grevillea tripartita. Visit isolated breakaways between the Ravensthorpe Range and the Stirlings and wonder at why Eucalyptus megacornuta, Eucalypts newbeyi and Eucalyptus talyuberlup are so similar but so different.
And while travelling amongst this excitement reflect on the fact that in the past 200 years Australia has seen more mammal extinctions than any other country in the world, that in south-western Australia 450 plant species face extinction in the wild due to current farming practices, and that only audacious restoration work like Gondwana Link can make a lasting difference.
We have been talking about biodiversity in terms of plants and animals but in fact the bulk of the amazing biodiversity is made up of fungi and invertebrates, whose importance to the health of ecosystems is largely ignored. Research into the fungi is many decades behind that of other organisms and there is little known (or understood) about their diversity and the role they play through most of the region. The majority remain unknown and any foray following rain will reveal new and interesting species – also new genera.
More than 90% of plants have symbiotic fungal partners which enable their survival (in nutrient-poor soils of southern Western Australia) by extracting essential minerals and passing them on through interaction inside the plants’ root cells. The seeds of native orchids can only germinate with the assistance of microscopic fungal partners. Some very complicated co-dependencies of fungi, mammals, invertebrates and plants are also beginning to reveal themselves. Australia has an abundance of small, truffle-like fungi (more species than anywhere else in the world) whose spores can only be distributed with outside assistance – such as that provided by Potoroos (Potorous gilbertii) and Woylies (Bettongia penicillata) which rely almost entirely on them for food. Fungi are also consumed by many other native animals and insects. Other kinds of fungi recycle organic matter (eg wood-rotting fungi) and make their contribution by returning nutrients to the ecosystem.
