Australia is one of the most biologically precious places on Earth, boasting nearly half a million species, most of them unique in the world. That's according to the latest special biodiversity issue of the CSIRO's science and environment magazine, Ecos .

But Ecos also reports that Australia's treasure trove of biological diversity is under threat - with vegetation clearing, feral plants and animals, illegal wildlife trafficking and the future greenhouse effect being the main culprits.

Ecos editor Bryony Bennett writes that Australia has an estimated 475,000 species of plants and animals, more than 80 per cent of which can be found nowhere else in the world.

She says biodiversity is a cornerstone of Australia's economy, supporting industries like agriculture, forestry and fisheries, and it is also responsible for providing life-supporting "services" to humanity - such as fresh air and water, food, medicines and industrial products.

Human activity has been changing Australia's ecosystems since the Aborigines first arrived about 60,000 years ago, Ms Bennett says, but over the past 200 years the pace of change has accelerated dramatically.

"Living systems can adapt to change," she writes. "But in 200 years many Australian environments have changed at an unprecedented rate, in many cases too fast for the flora and fauna to adapt. Nearly 90 per cent of temperate woodlands and mallee, and 50 per cent of the rainforests, have been cleared. More than 50 per cent of agricultural land now needs restoration because of salinisation, waterlogging, soil erosion and other degradation.

"One hundred plant species, 17 mammals and three birds have been lost. At least three frogs, including the unique gastric brooding frog of Queesland, seem to have disappeared. Many more species are threatened, endangered or extinct at a regional level."

Ms Bennett says clearing or severely modifying native vegetation, and inappropriate management, is the greatest threat to Australia's biodiversity. The greatest declines in native species have happened in the areas of Australia which support the bulk of the nation's sheep and wheat industries.

Often, she says, native species cling on for a while in fragments of the original ecosystem, and there can be a considerable time lag between land being cleared and animals finally vanishing. CSIRO research in Western Australia's wheat belt, for example, has found that birds are still disappearing now as a result of clearing which happened several decades ago.

Ms Bennet says the invasion of Australian landscapes by feral plants and animals is another threat to biodiversity. About 20 mammals, 30 birds, 21 fish, 500 insects and other invertebrates and 1,500 plants from other countries have become naturalised in Australia. They put pressure on native species by competing with them, as predators and parasites or by bringing exotic diseases. Land degradation by rabbits, and predation by foxes and cats, are a major cause of the extinction of Australia‚s mammals.

Ecos reports on the latest CSIRO research which is seeking ways to measure and protect biodiversity - often by studying "uncharismatic" animals like insects rather than the more familiar furry animals.

Biological diversity (or "biodiversity") means simply the variety of life on Earth. It includes three levels - genetic variation within a species, variation between different species and variation between different ecosystems.

The international Convention on Biological Diversity, which Australia and 36 other countries have ratified, came into force on December 29 last year. On December 16 Federal Cabinet approved the draft National Strategy for the Conservation of Australia's Biological Diversity.

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