Human Impacts

A. FARMING

In the 1800’s much of the Warnervale floodplain was cleared and fenced for cattle grazing – including the edges of PCW reducing the size of the wetland. Land around the wetland is still privately owned and fenced. Fencing affects the drainage of water but had limited impact as water still entered over a fairly broad area.

B. URBAN GROWTH

The major threat to Porters Creek Wetland comes from the rapid urban development occurring in the catchment. The increase on non-porous surfaces has changed the hydrology of the catchment resulting in excess water flowing directly into the wetland through a limited number of channels such as Fishburn Drain at Watanobbi. Stormwater from Watanobbi and urban subdivisions in Warnervale, Wadalba and Woongarah flows through the wetland bringing sediment and nutrients that promote the growth of weeds as well as directly depositing weeds during periods of heavy rain.

Where excess water enters the wetland there has been dieback of Woollybutt trees that do not like to have permanently “wet” feet (which is why they are found on the edges of the wetland). Dieback reduces habitats and food for bird species and small mammals such as possums.

C. EDGE EFFECTS

Edge effects” of urban development also include:

• domestic pets (kill native species)

• weeds eg Pampass Grass, Sagittaria from fish tanks,

• feral animals eg foxes, Gambusia (Mosquito fish)

• bushfires (reduce plant and animal diversity)

• rubbish - cars, garbage, shopping trolleys

• tracks and paths that allow people and animals into the heart of the wetland

D. POTENTIAL IMPACTS

The location of Warnervale airport means planes fly directly over the wetland. Noise and burnt fuel vapour can impact on species in the wetland. Noise is known to affect breeding and feeding patterns although no studies have been done on this for PCW. Pressure to extend the airfield is yet to be resolved. A future expansion of the airport could pose a big threat especially if the wetland is reduced in size and/or an extension of the runway fragments the wetland.

Nearby Industrial Developments (Employment zones) at North Wyong Industrial Estate and Warnervale Business Park pose potential threats from the leakage of chemicals and oil spills from visiting heavy vehicles and further land clearing for expansion. Plans for more industrial development in this area are continually proposed as does potential expansion or development of the airport site