AUSTRALIA'S BIODIVERSITY: A WORLD VIEW
Australia's biodiversity is very rich. In 1998 Conservation International recognised 17 countries as mega-diverse because of their extraordinarily rich biodiversity, and together they account for some two-thirds of the world's species. Australia and the USA are the only two developed countries classed as mega-diverse.(SEE FOOTNOTE 1)
Australia is a large country and contains a great variety of habitats and ecosystems, from coral reefs and tropical rainforests to temperate woodland, deserts, semi-arid rangelands and alpine grassland. It is, therefore, likely to have more species than many countries by virtue of size alone. But as the table below shows, our fauna is highly endemic (that is, many Australian species are found nowhere else on Earth). About 90% of our reptiles and frog species are endemic, and about 80% of our mammals and 85% of flowering plants.(SEE FOOTNOTE 2) We have 200 species of freshwater fish, 90% of which are endemic. Also, of the 600 species of finfish found in the southern temperate zone, about 85% are found only in Australian waters.(SEE FOOTNOTE 2) Conversely groups of animals and plants found in many other countries are not found naturally here. Hooved animals, cats, canids (foxes and Dingos) and plants like thistles, for example, have been introduced and affected native biodiversity.
Far less is known about the world of invertebrates and micro-organisms, though Australia has several hundred thousand such species, the majority of which have not been described.(SEE FOOTNOTE 2) There remains much to be learnt about our biodiversity. In 2000, for example, scientists announced the discovery of a new type of antibiotic - as powerful as penicillin - in the eggs of an Australian shellfish.(SEE FOOTNOTE 6)
The headline commentary focuses on threatened birds and mammals in Australia. This commentary explores other, wider aspects of biodiversity and some of the key pressures on it. The commentary looks in more detail at Australia's mammalian extinctions, and four case studies of endangered species illustrate how human activities can affect biodiversity.
|AUSTRALIA'S BOTANICAL DIVERSITY|
With over 15,500 species, Australia has more native higher plants (mainly flowering plants,)(SEE FOOTNOTE 3) than all of Europe (which has 12,500 species),(SEE FOOTNOTE 4) and Queensland and Western Australia each contain around 7,500 native species.(SEE FOOTNOTE 3) New species are still being discovered, like the Nightcap Oak, a large tree discovered in 2000 in northern NSW. There are possibly 10 times the number of cryptogams (fungi, algae, lichens, mosses, etc.) than higher plants, and we have barely begun to understand them.(SEE FOOTNOTE 5)
Numbers of species in selected countries(a)
(a) Data are approximate only and have been drawn from the World Resources Institute for the purpose of making international comparisons.
(b) Breeding species are used because some species are migratory.
Source: World Resources Institute.
PRESSURES ON BIODIVERSITY
Change, such as evolution, and disturbance are a natural part of every environment. But human activity almost invariably affects the direction and pace of change and the extent of disturbance, challenging the ability of ecosystems and species to respond.(SEE FOOTNOTE 7) Over the past 200 years, change in Australia has, by world standards, been great and rapid, and has had a profound effect on our biodiversity. The change has taken many forms, including large scale land clearance and the introduction of many exotic species, while the use of water, primarily for agriculture, has damaged the health of freshwater ecosystems.
Some of the threats to biodiversity are discussed elsewhere in this publication. Headline indicators of land clearance, soil degradation, inland waters, air quality and greenhouse gases each relate to areas of concern that affect our plants and animals as well as other aspects of progress.
Invasive species, marine ecosystems and land use are also discussed in supplementary commentaries. Another factor, discussed in the box below, is changes to the patterns of fire.
The changes since 1788 have had far-reaching effects on biodiversity. Species interact with one another and their environment in a complicated web of checks and balances that has developed over millions of years. A change to one part of the system can have important, sometimes unforeseen consequences elsewhere through a cascade of effects; the removal of native vegetation is an example. Clearing plants removes the food that herbivores rely on, and consequently impacts on the carnivores higher up the food chain. Removal of plants can lead to soil erosion or the loss of soil nutrients: both processes reduce the biodiversity present among the vast array of minute species tha live in the soil. And as a patchwork of vegetation is cleared, the remaining islands of native vegetation can be more vulnerable to damage from threats such as weed invasions, while the animals left within these islands may be isolated and so more vulnerable to events such as the bushfires in south-east Australia at the end of 2001.
| New Zealand|
| South Africa|
| United Kingdom|
Over the past 200 years many elements of Australia's biodiversity have declined, and species of mammals, birds, frogs and plants are presumed to have become extinct. Our mammals have been affected particularly severely: 17 of the 270 or so species of mammal that lived in Australia in 1788 are now presumed extinct, under the Environment Protection and Biodiversity Conservation Act 1999. Ten of these species were lost in the past 100 years.
The table below lists the mammal species (but not subspecies) that are believed to have become extinct in Australia since 1788. A further seven subspecies are presumed extinct, and several other species now survive on offshore islands or Tasmania but are extinct on the mainland. This compares with three extinct birds from about 700 species (another four subspecies have also become extinct), four extinct frogs from over 200 species, and 62 species of flowering plants from over 15,000 species. No freshwater fish or reptile species are known to have become extinct, though other species may have become extinct before they were ever recorded (and this is probably more likely for species of fish and plants than for birds and mammals because they are less well documented).
The numbers of extinctions in different States and Territories depend on many factors such as the types of ecosystems within a State, the level of human disturbance and the impact of exotic species. But among the States and Territories, South Australia has lost more mammals than any other State: 34 species of mammal are presumed extinct from that State (though here, as in other States, some of these animals continue to survive elsewhere in Australia). New South Wales has also lost many species (27), while the Northern Territory has lost an estimated 14 species. Victoria and Western Australia have both lost ten mammal species and Queensland five. The ACT does not maintain a list of extinct mammals, although in recent times only one species is believed to have been lost (the Brush-tailed Rock Wallaby), while Tasmania is thought to have lost the Thylacine but no other mammal species since 1788.
Mammalian extinctions(a) since 1788
|FIRE AND BIODIVERSITY|
There is a growing awareness of the links between fire regimes (the season, frequency, intensity and type of fires) and conservation of biodiversity. In northern Australia in particular, many animals depend on a certain pattern of fires for survival.
Experts think that fires have tended to be less frequent since European settlement than they were when Indigenous Australians managed the land. However, these less frequent fires have had more fuel to power them, and they have been more intense and, in some areas, more destructive as a result. In other parts of Australia, by contrast, experts believe that a higher frequency of low intensity fires can be more damaging to biodiversity than less frequent high intensity fires. Different fire regimes impact differently on different species, and scientists are only beginning to understand the importance and complexity of planning and implementing fire regimes.(SEE FOOTNOTE 8)
(a) excludes subspecies and extinctions from Christmas Island. Source: A Gap in Nature (SEE FOOTNOTE 10) and Mammals of Australia (SEE FOOTNOTE 11).
| Darling Downs Hopping Mouse|
| Big-eared Hopping Mouse|
| White-footed Rabbit Rat|
| Gould’s Mouse|
| Broad-faced Potoroo|
| Eastern Hare-wallaby|
| Short-tailed Hopping Mouse|
| Long-tailed Hopping Mouse|
| Pig-footed Bandicoot|
| Lesser Stick-nest Rat|
| Desert Rat-kangaroo|
| Toolache Wallaby|
| Lesser Bilby|
| Crescent Nailtail Wallaby|
| Central Hare-wallaby|
| Desert Bandicoot|
|Many endangered species face more than one threat. The box below looks in more detail at four of Australia's endangered animals, and discusses why they are assessed by the Commonwealth Government as threatened and what is being done to protect them.|
Gilbert's Potoroo (Potorous gilbertii) is possibly the rarest mammal in the world. This rabbit-sized marsupial was thought to have become extinct last century. But in 1994 it was rediscovered at Two Peoples Bay Nature Reserve, near Albany in south-west Western Australia. Only about thirty of these small rat-kangaroos are thought to remain, and efforts to breed the animals in captivity are hampered by the potoroo's preferred diet of truffle-like underground fungi, which are very hard to find in sufficient quantity to feed captive animals.
Gilbert's Potoroo is thought to have been driven to the brink of extinction through predation by foxes and cats and the loss of its native habitat from land clearance, fires and more recently the introduced Dieback Fungus (Phytophthra cinnamomi). Scientists believe that it clung on in Two Peoples Bay because the area has escaped significant fires for the past 50 years or more.
PROSERPINE ROCK WALLABY
The endangered Proserpine Rock Wallaby (Petrogale persephone), which was unknown to science until 1976, is found only in a small area of Whitsunday Shire on the central Queensland coast and nearby Gloucester Island. Because it occupies such a small area, it is extremely vulnerable to habitat loss, particularly from land clearing for tourist and residential developments around Airlie Beach. They are also threatened by predation from dogs and cats, road traffic and diseases spread by cats.(SEE FOOTNOTE 9) The rock wallaby recovery team is working with the local council and developers to minimise the impacts of developments on the animals and their habitat.
The Regent Honeyeater (Xanthomyza phrygia) has declined from a common woodland bird of the 1800s to an endangered species with a population estimated at fewer than 1,500 birds. The honeyeaters feed on nectar from flowering trees, and relied on those forests in south-eastern Australia that were particularly nectar-rich (such as White and Yellow Box woodland). These forests grew on the richest and most fertile soil and have been extensively cleared for agriculture; as the forests disappeared so did the honeyeaters.
Regent Honeyeaters are now found regularly in only three areas. The small town of Barraba in northern New South Wales has embraced the bird as its emblem and is encouraging eco-tourists to the area. In Chiltern, Victoria and the Capertee Valley in New South Wales, local communities are working to protect the honeyeaters' habitat by revegetating land. Revegetation is also helping to control salinity and erosion.
BRIDLED NAILTAIL WALLABY
The endangered Bridled Nailtail Wallaby (Onychogalea fraenata) once ranged through the semi-arid inland from the Murray River in Victoria to Charters Towers in north Queensland. In the early 1900s it was hunted for its beautiful pelt. It was thought to have become extinct because there were no confirmed sighting after 1937. In 1973 Darryl Challacombe read a magazine article about wildlife and realised that he often saw 'extinct' Bridled Nailtail Wallabies where he worked: a few hundred wallabies remained near Dingo in central Queensland. The two properties where the animal was observed were acquired as reserves, and some wallabies were relocated to Idalia National Park in western Queensland in 1993; their numbers are increasing.
In central Queensland at least, the decline of the wallaby appears to be associated with the pastoral industry: stock competed with the wallaby for food and disturbed ground cover. Dingos and cats prey upon the wallaby in Queensland, while further south, foxes once hunted the wallaby before it disappeared.
|A LONGER TERM VIEW|
Declines in wildlife have occurred in most parts of Australia since European colonisation. Over the past 200 years 17 mammal species are thought to have become extinct here. Fewer than 25 species are believed to have become extinct in the rest of the world over the same period, which means that Australia accounts for over 40% of the world's mammalian extinctions since 1800-10 Some other mammals, once widespread, now survive only in tiny areas (often islands free of foxes and cats); this isolation and loss of genetic diversity make species less adaptable and more vulnerable to threats such as disease.
Intensive land use, which has played a part in the decline, has been concentrated in the south and east of the country. Habitat loss, through cropping, grazing, forestry, mining and human settlements, has dramatically changed vegetation cover. The 1996 State of the Environment report assessed that since 1788:
- over 40% of forests had been cleared;
- more than 60% of coastal wetlands in southern and eastern Australia had been lost;
- about 75% of rainforests had been cleared;
- almost 90% of temperate woodlands and mallee had been cleared; and
- more than 99% of temperate lowland grasslands in south-eastern Australia had been lost.(SEE FOOTNOTE 2)
Wildlife has declined in northern and central Australia too, where the level of land clearing has been lower. In the arid zone, about one-third of mammal species are regionally extinct, the highest extinction rate on the Australian mainland, and many birds are declining.(SEE FOOTNOTE 2) The extent of cattle grazing, effects of invasive species and changes to fire regimes are factors thought to have led to a decline in many animal species in these areas.
1 Conservation International 1998, electronically published on the Internet in 1998. URL: www.organisation.org/web/fieldact/megadiv/megadiv/htm.
2 State of the Environment Advisory Council 1996, Australia - State of the Environment Report 1996, CSIRO Publishing, Melbourne.
3 Australian National Botanic Gardens 1998, Australian Flora & Vegetation Statistics, URL: http://www.anbg.gov.au/anbg/australian-flora-statistics.html last viewed 14 February 2002.
4 IUCN Species Survival Commission News Release 12.0701, .SSC expertise called on for strategy to save Europe's plants., IUCN, Switzerland, URL: www.iucn.org/themes/ssc/pressreleases/plantstrategy.html last viewed 18 February 2002.
5 Mill, J. and Hall, F. 2000, Protecting Threatened Plants, The Australian Network for Plant Conservation, Canberra.
6 Benkendorff, K., Bremner, J.B. and Davis, A.R. 2000, "A putative role for the precursors of Tyrian Purple in the egg masses of the Australian Muricid, Dicathaisorbita", Journal of Chemical Ecology, 26.
7 Saunders, D., Hopkins, A., and How, R. 1990, "Australian Ecosystems: 200 Years of utilization, degradation and reconstruction", in Proceedings of the Ecological Society of Australia, 16, ESA, Canberra.
8 Gill, A.M, Groves, R.H. and Noble I.R. (eds) 1981, Fire and the Australian Biota, Australian Academy of Science, Canberra.
9 Barry Nolan, Queensland Parks and Wildlife Service personal communication.
10 Based on information in Flannery, T. and Schouten, P. 2001, A Gap in Nature, Text Publishing, Melbourne; and data from the Committee for Recently Extinct Organisms, URL: www.crea.amnh.org last viewed 22 February 2002.
11 Strahan, R. 1995, The Mammals of Australia, Reed Books, Chatswood, NSW.
|Seventeen species of mammals (and another 10 subspecies) are listed by the Commonwealth as presumed extinct in Australia since 1788. Ten of these species were last seen alive in the twentieth century, ten of these animals are marsupials, and 14 of them were found predominantly in the inland arid zone. However, other groups of animals have fared rather better, at least in terms of losses through extinction. |