Threats

Wind Erosion Scalds. Press image to enlarge.

Wind Erosion Scalds. Press image to enlarge.

When the first European explorer, John Oxley, came across the Macquarie Marshes in 1818, he found that they were the home of a thriving Aboriginal community known as the Wailwan people. Charles Sturt in 1828 commented that the traditional owners used fire to access the reed beds and flush out their game.

However when European settlers began to arrive with their flocks and herds in the 1840’s, humans began to impact significantly on the Macquarie Marshes.

In some areas the combination of overgrazing by sheep and cattle, and later rabbits, removed all the vegetation and exposed the topsoil, which then blew away. The resulting bare claypans are called scalds.

During dry years cattle tend to live in the reed beds, eating the reeds and trampling pathways or pads through them. These pathways then become eroded into channels during the next wet spell. Water travelling down these eroded channels no longer floods out onto the reed beds, and they die. In this way 60% of the reed beds of the South Marsh (around 2,200 hectares) were lost by 1963.

Cattle graze and trample reed beds. Press image to enlarge.

Cattle graze and trample reed beds. Press image to enlarge.

The settlers realised that they could easily create more flooding on their land by blocking off some waterways, or building levee banks across shallow waterways. Since 1980 the size and number of these banks has increased, significantly reducing the flooding of downstream wetlands.

Levee Bank Upstream of South Marsh. Press image to enlarge.

Levee Bank Upstream of South Marsh. Press image to enlarge.

Another effect of changing the flow has been that trees in some ephemeral shallow creeks like the Terrigal Creek have been drowned.

The Macquarie Marshes have a long history of tree clearing for pasture and cropping, with huge areas cleared in the 1970’s. Today dead trees are a common sight in the Marshes. The causes include drowning, salinity, ringbarking, fire and poisoning.

If the surface flooding of River Redgum forests is reduced, they can be forced to use the highly salty groundwater, which kills them.

For more information on the history of human impacts on the Macquarie Marshes seeĀ “The Macquarie Marshes: an Ecological History”.

Drowned trees in the Terrigal Creek. Press image to enlarge

Drowned trees in the Terrigal Creek. Press image to enlarge

Grazed to left, ungrazed to right of fence line. Press image to enlarge. Photo Peter Solness

Grazed to left, ungrazed to right of fence line. Press image to enlarge. Photo Peter Solness

Dead trees unknown cause. Press image to enlarge.

Dead trees unknown cause. Press image to enlarge.

Salinity in the North Marsh. Press image to enlarge

Salinity in the North Marsh. Press image to enlarge