| Changes to Natural Hydrology
Natural flooding and drainage patterns have been altered throughout the river system. At many wetlands, the seasonality, duration, extent and frequency of flooding and drying have been altered. Some wetlands have been deprived of their natural flooding, while others have been degraded by permanent or near-permanent inundation due to river regulation. These changes have disrupted breeding triggers for native wildlife and reduced the wetland habitat diversity and ecological productivity.
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Changes to Water Quality
Water quality changes have been caused by disposal disposal of urban or rural waste water and poor management of surrounding land. These changes disturb the ecological processes within wetlands and lead to the loss of aquatic plants and habitat. The altered habitat often favours nuisance species, such as blue-green algae, and Common Carp, over native species.
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| Salinisation
In many areas of Australia, river regulation, irrigation practices and vegetation clearing are bringing saline groundwater closer to the surface. Wetlands, the lowest areas of the landscape, are usually the first areas affected by shallow watertables. Salinisation brings drastic changes to the vegetation and habitat of a wetland and restricts the options for managing flood inflows and recession.
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Pest Plants and Animals
Introduced pest species disturb and alter the habitat of native fauna and compete with native species. Common Carp, in particular has infested many wetlands throughout the Murray-Darling Basin. The inundation of wetlands by regulated flows over summer has created favourable breeding conditions for this species and given it an advantage over native fish.
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| Agricultural Use
Development of wetland areas for agricultural production, such as lake bed cropping, irrigation or water storage, disturbs natural processes and may remove native vegetation. Excessive stock grazing of wetland vegetation may alter the mix of plant species and change the habitat for native fauna. Stock may also trample plants and disturb sediments and the invertebrates that those sediments support.
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Surrounding Land Uses
The management of surrounding areas affects the condition of a wetland. Erosion from these areas causes excessive sedimentation and may carry nutrients and agricultural chemicals to the wetland. The fringe of native vegetation protects a wetland from such disturbances and is also an integral part of the wetland ecosystem. This fringing vegetation must be protected to maintain the diversity of habitats for native fauna and to minimise the impacts of surrounding activities.
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