Revegetation consultant Merrick Savage said red gums needed to have their roots permanently in the water table and his observations of the deteriorating health of these ‘Mount Wedge form’ red gums supported reports from local farmers that water extraction from the Polda Basin had lowered the water table.

Merrick has visited the area regularly for more than 20 years to harvest seed from trees, including these red gums.

He first noticed dieback on the red gums in 2005-06, while red gums closer to Mount Wedge remained healthy.

The health of these trees continued to decline until November 2009, he said, when many of the trees had a flush of new foliage.

Younger red gums have a smaller crown and root biomass, according to the expert, giving them less ability to survive extended periods of water stress. He said there is already evidence these semi-mature red gums are suffering extreme moisture stress.

“Without extended periods of flooding and surface water, the long-term survival of many of these trees is becoming increasingly unlikely,” he said.

Merrick Savage is also concerned about the future of the Polda red gum population because the trees have produced little viable seed in the last decade and unless high levels of moisture are sustained into summer very few plants will survive.

“If, as the Polda farmer group suggests, the water table has been lowered to unsustainable levels the likelihood of prolonged periods of surface water and the survival and recruitment of young red gums will become increasingly remote.

“In other words we are watching the extinction of several generations of Polda red gums.”

SA Water has stopped pumping from the Polda Basin and a Water Allocation Plan is being developed to decide who can pump from the basin in the future and how much.