Moreover, studies in Australia’s wet tropics show that soils have limited capacity to recover from deforestation. This adds to deforestation’s price tag. Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) estimates that land degradation costs about $1 billion annually.
Overgrazing is one of the main pressures on biodiversity in Australia. Grazing and various agricultural improvement strategies have modified vast areas of grasslands and open grassy woodlands. In temperate ecosystems, less than 2% of the original grasslands remain.
Moreover, overgrazing promotes desertification and erosion, and is also seen as one cause of the spread of invasive plants.
In 2005, 17 of 82 species that were assessed in Australian waters were classified as overfished. Species that remain subject to overfishing and/or are overfished include the southern bluefin tuna; blue warehou; silver trevally; orange roughy; and bigeye tuna in the Pacific and Indian Oceans beyond the Australian Fishing Zone (AFZ).
Illegal fishing places further pressure on some species, with patagonian toothfish in the Southern Ocean and shark (for fins) in northern Australian waters being the worst affected.
Historically, feral cats, foxes and rabbits have been a cause of local extinctions and significant reductions in range for native species through a combination of habitat modification and predation. They are a major ongoing problem.
Weeds are an equally significant pressure on ecosystems, with more than 2,500 species of introduced plants now thriving in the wild in Australia. They have invaded every part of the landscape – bushland, rangelands, coasts, rainforests, deserts and farms.
Ballast water from shipping has been responsible for introducing more than 250 species, and possibly as many as 500 species, into Australian waters.
- Beeton RJS (Bob), Buckley Kristal I, Jones Gary J, Morgan Denise, Reichelt Russell E, Trewin Dennis (2006 Australian State of the Environment Committee) 2006, Australia State of the Environment 2006. Independent report to the Australian Government Minister for the Environment and Heritage, Department of the Environment and Heritage, Canberra.
- FAO. 2005. Global Forest Resources Assessment. FAO Forestry Paper 147.
- McLoughlin, K. (ed.) (2006) Fishery Status Reports 2005: Status of Fish Stocks Managed by the Australian Government. Bureau of Rural Sciences, Canberra.
- V. Rasiaha, S.K. Florentineb , B.L. Williamsb, M.E. Westbrooke. 2003. The impact of deforestation and pasture abandonment on soil properties in the wet tropics of Australia.