State of the Environment 2011 (SoE 2011)
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to
the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
8 Biodiversity
2 State and trends of biodiversity
At a glance
We have limited information on the state of many individual species or groups of species. However, the evidence from changes in extent, composition and quality of vegetation communities, and from case studies on selected species, points towards continuing decreases in population sizes, geographic ranges and genetic diversity, and increasing risks of population collapses in substantial proportions of most groups of plants, animals and other forms of life across much of Australia. This trend is variable, because components of biodiversity appear to be persisting well in some areas, especially where human impacts are minimal, but declining significantly in others. Historically, problems have been greater in southern Australia than in the north, especially in woodlands and grasslands of the agricultural zones of the south-east and south-west. However, recent reports of significant decreases in abundance in small mammals and birds in northern Australia suggest that at least some components of biodiversity in the north are less secure than previously thought.
The limited amount of long-term data on virtually all groups of plants, animals and other organisms means that Australia has a very poor ability to assess rates and directions of change in elements of biodiversity, and to assess whether or not some components might be approaching points at which much more rapid change might occur, beyond which return to previous conditions might be very difficult or impossible. Research from around the world and case studies within Australia suggest that such threshold change is a possibility in a number of places and ecological systems. Where it occurs, it is likely to lead to irreversible loss of biodiversity.
When many people think of biodiversity, they usually think of the number of individual species, especially those that are very visible. ‘Species diversity’, however, is only one part of biodiversity, and it depends on other types of diversity. The short and long-term survival of species depends in part on the options that their genetic diversity gives them for adapting to change. The capacity of animals to find food and mates and successfully raise young is also influenced by the extent, diversity and quality of the habitat that is available, interrelationships with other species at a range of scales from a few millimetres to whole landscapes (and even at global scales for migratory species), and interactions with nonliving components of the environment, like temperature, rainfall, fire regimes and soil type.
Therefore, at least three levels of information are considered in this section on the state of Australia’s biodiversity:
- an assessment of the degree to which ecosystems—suites of species interacting with one another and the nonliving environment—continue to exist across their past ranges
- an assessment of the quality of remaining native vegetation (e.g. whether it contains a diversity of structure, minor and major species, resources and ecological processes)
- information on the distribution and abundance of individual species and particular groups of species (e.g. ecological communities).
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