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Arborist says pine forest is dying

Originally published on 29 July 2004

A combination of climatic conditions and an unsuitable environment are killing a 46-year-old Norfolk Island Pine grove at Mackay Harbour.

Curator of the Brisbane Botanic Gardens, Ross McKinnon, today provided the Mackay Port Authority with a detailed health report on the pine and palm trees at the northern end of old Mulherin Park.

The report was commissioned after concerns the trees were deteriorating and could pose a safety threat to park users and picnickers.

Mr McKinnon said the trees were showing signs of marked degeneration due to saltwater inundation and their advanced age.

Their amenity value and safety must now be questioned, he said.

It has been my observation that Norfolk Island Pines have a life span of 80 to 100 years under ideal growing conditions.

These Mackay foreshore pines have grown in far less than ideal conditions and their removal for safety reasons appears imminent.

Mr McKinnon - one of Queensland's most respected arborists - said the harbour pines were already showing marked signs of age deterioration with a number now totally dead and many stressed and in the last five years of life.

He said the trees were originally planted too close together.

Removal of every second pine tree would not alleviate root competition, remaining tree deterioration or general health, Mr McKinnon said.

Combined with a sand soil profile, these sands have readily absorbed vast quantities of salt/sea water from tidal surges. I know of no tree other than mangrove species that can withstand saltwater inundation for even short periods of time without deleterious affects.

Constant salt laden winds (10-15 knots), storms and cyclones are not uncommon to Norfolk Pines in their natural habitat but salt on the waxy pine needles does, in aging trees, have an accumulating effect and is a contributing factor to their deterioration and death.

Mr McKinnon said the trees were unsuitable for replanting.

Mackay Port Authority's environmental manager Scott Keane said a decision had yet to be made on the future of the grove.

A number of factors will come into play, including the observations made by Mr McKinnon in his report, he said.

We are talking about a public safety issue here - and the MPA has a duty of care to ensure the grove is maintained in a safe condition. Our workers have been busy over the past few weeks removing dead branches that have fallen from the pine trees in strong winds.

Mr Keane said another six trees have been identified as unsafe and would be removed later this week.