Two main drivers of change were identified; climate and human activities.
The stressor model shows that there are two main drivers of change climate and human activities.
Actual or likely threat or threatening activities Potential impact(s) to wetland components; processes and or services Affected ecosystem service Related components and processes Likelihood Timing of threat Significance of impact to ecological character (and extent) Climate change Changed rainfall patterns Changed frequency and intensity of flood events Climate regulation Changes to hydrology and tidal regime leading to changes in Biodiversity wetland communities and associated species.
Climate The climate of the area is maritime with average diurnal temperatures ranging from a minimum of 8.4 C to a maximum of 25.5 C over the year (Figure 2 2).
Two main drivers of change were identified; climate and human activities.
The stressor model shows that there are two main drivers of change climate and human activities.
Actual or likely threat or threatening activities Potential impact(s) to wetland components; processes and or services Affected ecosystem service Related components and processes Likelihood Timing of threat Significance of impact to ecological character (and extent) Climate change Changed rainfall patterns Changed frequency and intensity of flood events Climate regulation Changes to hydrology and tidal regime leading to changes in Biodiversity wetland communities and associated species.
Climate The climate of the area is maritime with average diurnal temperatures ranging from a minimum of 8.4 C to a maximum of 25.5 C over the year (Figure 2 2).
Climate change; including changes in the timing and extent of rainfall events; and water extraction can alter the tidal balance of the estuary.
Major threats that were identified which may lead to significant changes in the ecological character of the Hunter Estuary Wetland Ramsar site are changes in tidal range due to dredging and flood mitigation and drainage works and increased sedimentation (as a result of past catchment clearing) leading to mangrove expansion and resulting in saltmarsh decline and changes in freshwater saltwater balance due to changes in land drainage and exclusion of tidal waters leading to saltmarsh decline.
There has also been an increase in the number of red necked avocet from 100 in the mid 1980s to over 5;000 in 2007 possibly related to long term drought in the inland causing avocets to move to coastal wetlands where there is permanent water.
Major threats that were identified by the stressor model which may lead to significant changes in the ecological character of the Hunter Estuary Wetland Ramsar site are changes in tidal range due to dredging and flood mitigation and drainage works and increased sedimentation (as a result of past catchment clearing) leading to mangrove expansion and resulting in saltmarsh decline and changes in freshwater saltwater balance due to landward drainage leading to saltmarsh decline.
Nutrients There has been a long term increase in oxidised nitrogen since the time of listing in all zones analysed; although part of that increase can be attributed to a wet weather bias of the measurement program after 1985 (Sanderson and Redden 2001a).
The increase in area of common reed has been attributed to the decline in salinity in the soils due to the absence of saltwater inflows because of the installation of flood mitigation structures (e.g. floodgates; and levees) during the 1970s (Greenwood and MacFarlane 2006).
The decline in saltmarsh has been attributed to the expansion of mangrove forests which has been associated with a number of factors including changes in rainfall; changes in sediment deposition and nutrient loads within the estuary increased tidal range caused by harbour; river channel and mouth dredging combined with the construction of rock training walls for land reclamation and the construction of flood gates on tidal creeks and rivers within the Hunter Estuary.
Large flood events such as these can dramatically alter the ratio of freshwater to salt water in the estuary for a short period of time.
They include an increase in flood frequency; drainage works within and adjacent to the Ramsar site; altered tidal regimes and a change in sediment deposition caused by the installation of flood mitigation structures; dams and weirs on the Hunter River and its tributaries.
Erskine (1981) suggested that there has been an increase in flood frequency in the Hunter Valley over the past 50 years because of changes to the seasonal pattern and total rainfall in eastern Australia; namely an increase in summer rainfall as well as a smaller increase in winter rainfall (Tucker 1975; Cornish 1977).
The drying of the saltmarsh combined with an increase in fresh water runoff resulted in a decline in salinity and allowed the colonisation of salt tolerant grasses and the subsequent transition of saltmarsh to saline pasture.
The drying of the saltmarsh combined with an increase in fresh water runoff has resulted in a decline in salinity resulting in a change in floristic composition.
Major threats that were identified which may lead to significant changes in the ecological character of the Hunter Estuary Wetland Ramsar site are changes in tidal range due to dredging and flood mitigation and drainage works and increased sedimentation (as a result of past catchment clearing) leading to mangrove expansion and resulting in saltmarsh decline and changes in freshwater saltwater balance due to changes in land drainage and exclusion of tidal waters leading to saltmarsh decline.
There has been a 9 increase in the area of mangrove forests and a 41 decrease in the area of saltmarsh within the Hunter Estuary Wetlands since the time of listing in 1984; which has been attributed to a change in tidal range caused by dredging; flood mitigation works (floodgates; levees) and constriction of the river channel in the upper estuary.
There has also been an increase in the number of red necked avocet from 100 in the mid 1980s to over 5;000 in 2007 possibly related to long term drought in the inland causing avocets to move to coastal wetlands where there is permanent water.
Major threats that were identified by the stressor model which may lead to significant changes in the ecological character of the Hunter Estuary Wetland Ramsar site are changes in tidal range due to dredging and flood mitigation and drainage works and increased sedimentation (as a result of past catchment clearing) leading to mangrove expansion and resulting in saltmarsh decline and changes in freshwater saltwater balance due to landward drainage leading to saltmarsh decline.
The increase in area of common reed has been attributed to the decline in salinity in the soils due to the absence of saltwater inflows because of the installation of flood mitigation structures (e.g. floodgates; and levees) during the 1970s (Greenwood and MacFarlane 2006).
The decline in saltmarsh has been attributed to the expansion of mangrove forests which has been associated with a number of factors including changes in rainfall; changes in sediment deposition and nutrient loads within the estuary increased tidal range caused by harbour; river channel and mouth dredging combined with the construction of rock training walls for land reclamation and the construction of flood gates on tidal creeks and rivers within the Hunter Estuary.
Large flood events such as these can dramatically alter the ratio of freshwater to salt water in the estuary for a short period of time.
They include an increase in flood frequency; drainage works within and adjacent to the Ramsar site; altered tidal regimes and a change in sediment deposition caused by the installation of flood mitigation structures; dams and weirs on the Hunter River and its tributaries.
Erskine (1981) suggested that there has been an increase in flood frequency in the Hunter Valley over the past 50 years because of changes to the seasonal pattern and total rainfall in eastern Australia; namely an increase in summer rainfall as well as a smaller increase in winter rainfall (Tucker 1975; Cornish 1977).
The drying of the saltmarsh combined with an increase in fresh water runoff resulted in a decline in salinity and allowed the colonisation of salt tolerant grasses and the subsequent transition of saltmarsh to saline pasture.
The drying of the saltmarsh combined with an increase in fresh water runoff has resulted in a decline in salinity resulting in a change in floristic composition.

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