Wetland ecosystem condition: extent of inundation
Indicator Status: For Advice
Department of the Environment and Heritage
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Why do we need to measure the extent of wetlands?
Wetland ecosystems, by definition, require inundation. Many significant wetlands (e.g. the Macquarie Marshes, the Gwydir and Millewa wetlands) are in regulated river systems and hence their flooding and drying cycles are 'managed'. It is critical to sustaining certain water depths in wetlands for the duration of important ecological events including fish and waterbird breeding, and for the control of invasive species.
Wetlands may be classified or described on the basis of the length of time during which water exists within the wetland over annual (12 month) or longer cycles and the area of wetland flooding. Boulton and Brock (1999) suggested that temporary wetlands can be classified on the basis of duration of filling and predictability of filling according to the following scheme modified from Boulton and Brock (1999) and Paijmans et al. (1985). Under this scheme, wetlands range from ephemeral to permanent and undergo natural changes in spatial extent and the depth of inundation according to water regime. Water regime involves timing, frequency and variability of water, as well as the duration and extent of the wetting and drying cycle. To maintain the health of wetlands, the water regime supplied to a wetland will need to mimic, as far as possible, these natural conditions. Monitoring the extent of inundation provides an indication of the degree in which the current water regimes differs from estimated natural conditions.
How will measuring the extent of wetlands assist in maintaining wetland health?
Measuring the extent of a wetland will assist in reporting on investments related to wetlands that are made under regional plans and address the matter for target: the integrity of inland aquatic ecosystems (rivers and other wetlands).
The Natural Heritage Trust (NHT) has identified the following as necessary areas of activity:
- protecting and restoring significant freshwater, marine and estuarine ecosystems; and
- protecting and restoring the habitat of threatened species, threatened ecological communities and migratory birds,
The National NRM Standards and Targets Framework has identified the following as required national resource condition outcomes:
- that the extent, diversity and condition of native ecosystems are maintained or rehabilitated;
- that populations of significant species and ecological communities are maintained or rehabilitated; and
- that ecosystem services and functions are maintained or rehabilitated.
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