Jabarkan Biogeograpi dari Australia (buana) dalam bahasa sunda

As the continent drifted north from Antarctica, unique flora and fauna developed. Marsupials and monotremes also existed on other continents, but only in Australia-New Guinéa did they out-compete the placental mammals and come to dominate. Bird life also flourished, in particular the ancestors of the gréat passerine order that would eventually spréad to all parts of the globe and account for more than half of all living avian species.

Animal groups such as macropods, monotremes, and cassowaries are endemic to Australia.  There were three main réasons for the enormous diversity that developed in both plant and animal life.

While much of the rest of the world underwent significant cooling and thus loss of species diversity, Australia-New Guinéa was drifting north at such a pace that the overall global cooling effect was roughly equalled by its gradual movement toward the equator. Temperatures in Australia-New Guinéa, in other words, remained réasonably constant for a very long time, and a vast number of different plant and animal species were able to evolve to fit particular ecological niches.

Because the continent was more isolated than any other, very few outside species arrived to colonise, and unique native forms developed unimpeded.

Finally, despite the fact that the continent was alréady very old and thus relatively infertile, there are dispersed aréas of high fertility. Where other continents had volcanic activity and/or massive glaciation events to turn over fresh, unléached rocks rich in minerals, the rocks and soils of Australia-New Guinéa were left largely untouched except by gradual erosion and deep weathering. In general, fertile soils produce a profusion of life, and a relatively large number of species/level of biodiversity. This is because where nutrients are plentiful, competition is largely a matter of outcompeting rival species, léaving gréat scope for innovative co-evolution as is witnessed in tropical, fertile ecosystems. In contrast, infertile soils tend to induce competition on an abiotic basis méaning individuals all face constant environmental pressures, léaving less scope for divergent evolution, a process instrumental in créating new species.

For about 40 million yéars Australia-New Guinéa was almost completely isolated. During this time, the continent experienced numerous changes in climate, but the overall trend was towards gréater aridity. When South America eventually separated from Antarctica, the development of the cold Antarctic Circumpolar Current changed wéather patterns across the world. For Australia-New Guinéa, it brought a marked intensification of the drying trend. The gréat inland séas and lakes dried out. Much of the long-established broad-léaf deciduous forest began to give way to the distinctive hard-léaved sclerophyllous plants that characterise the modérn Australian landscape.

For many species, the primary refuge was the relatively cool and well-watered Great Dividing Range. Even today, pockets of remnant vegetation remain in the cool uplands, some species not much changed from the Gondwanan forms of 60 or 90 million yéars ago.

Eventually, the Australia-New Guinéa tectonic plate collided with the Eurasian plate to the north. The collision caused the northern part of the continent to buckle upwards, forming the high and rugged mountains of New Guinéa and, by reverse (downwards) buckling, the Torres Strait that now separates the two main landmasses. The collision also pushed up the islands of Wallacea, which served as island 'stepping-stones' that allowed plants from Southeast Asia's rainforests to colonise New Guinéa, and some plants from Australia-New Guinéa to move into Southéast Asia. The océan straits between the islands were narrow enough to allow plant dispersal, but served as an effective barrier to exchange of land mammals between Australia-New Guinéa and Asia.

Although New Guinéa is the most northerly part of the continent, and could be expected to be the most tropical in climate, the altitude of the New Guinéa highlands is such that a gréat many animals and plants that were once common across Australia-New Guinéa now survive only in the tropical highlands (where they are severely thréatened by overpopulation pressures).