Environmental ‘skin graft’ helps heal scars on Lake Mac landscape

Lake Macquarie City Council

An earthmover scrapes topsoil and its embedded seed bank and organisms from the donor site, ready to be trucked to the rehab site 800m away.jpg

An environmental “skin graft” that could revolutionise how local developers rehabilitate bushland is under trial in Lake Macquarie.

Lake Macquarie City Council is working alongside developer Hammersmith and civil engineering firm KCE at the Cameron Grove residential development, where bushland is being cleared to make way for 650 new homes.

Usually, developers clearing land are required to plant out offset sites with tube-stock seedlings, which often have high attrition rates and require regular care and maintenance.

Under the trial, the top 10-20cm of soil and leaf litter on the site to be cleared is scraped off and collected, then spread 20-30cm deep at a nearby rehabilitation site.

Manager Environmental Systems Karen Partington said on normal development sites, the nutrient-rich material is simply sent to green waste or used on-site as landfill.

Using the trial technique, the material will cover about 2000sqm of land about 800m away, healing scars on the landscape left by illegal rubbish dumping and four-wheel drive vehicles.

“Similar methods employed in other parts of NSW have been promising, with a greater diversity of plants and a higher chance of survival,” she said.

“Traditional offset planting is excellent, but there are limitations. It’s often difficult and expensive to maintain, and you simply can’t get the range of plants endemic to any given area from a nursery and plant them out.”

“Scraping off that top layer of soil captures the natural seed bank, as well as all the vital organic matter and organisms that help new plants grow.”

The trial donor site to be cleared covers about 4000sqm, with 600 cubic metres of soil to be removed – equivalent to about 70 truckloads.

Logs from trees felled as part of the residential development have also been reused to help minimise erosion at the rehab site.

“We’ll monitor the site over the next two years, which should give us a great indication of whether this method is an effective and viable alternative to traditional replanting,” Ms Partington said.

“If it is, it could change the way we approach offset planting here in Lake Macquarie and beyond, improving results and reducing costs for both Council and developers.”

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