Regeneration of dunes in Byron Shire

Byron Shire Council received financial support from the NSW State Government’s Environmental Trust to undertake regeneration of dunes in the Shire. Bitou Bush, now declared a weed of national significance, was replanted to mined sites to control erosion, resulting in extensive dominance of the coastal zone at the expense of native ecosystems

The project has allowed Council to engage with volunteers, contractors and the general community to significantly reduce the extent of Bitou Bush in the Shire.

• A Bitou background
• To spray or not to spray
• Battle of the Bitou

A Bitou background

One of the great ironies of Bitou Bush is that it was once considered an ally in an earlier battle to save the dunes.

Plantings of the South African shrub were undertaken from 1946 to 1968 - on the recommendation of the Soil Conservation Service of NSW - in a bid to stop the erosion of denuded dunes after the devastation wrought by sand mining.

“I know people who remember when it was being propagated and planted along the coast,” says Byron’s Bush Regeneration team leader, Heidi Lunn. “And now it’s become a Weed of National Significance.”

Bitou Bush (Chrysanthemoides monilifera ssp. rotundata) is recognised by its bright green serrated leaves (usually much brighter than surrounding native vegetation) with yellow, daisy-like flowers. Young plants are often covered in a white cottony down.

While it predominantly grows as a low coastal shrub (1-2m), Bitou has the ability to climb over other vegetation, eventually smothering even quite tall plants. It outperforms many native plants, threatening their habitats and endangering entire species.

“Because it is so leafy, you don’t get a lot of things [growing] underneath it,” says Heidi

“But once you spray it out a lot of things do germinate.”

Despite the success of the recent program, Bitou has extraordinary regenerative powers. So the more people who know how recognise it the better.

Each mature bush can produce up to 48,000 seeds a year, which can survive up to seven years. The small black fruit are attractive to native birds such as silvereye and Lewin’s honeyeater, which distribute seeds far and wide.

Council is encouraging local people to keep an eye out – and to take another look around their own gardens. A few kilometres from one of the eradication sites, we spotted Bitou Bush growing in the front yard of a private home.

To spray or not to spray

According to the 2005 Regional Weed Management Plan, 90 percent of the Northern NSW coastline was infested by Bitou Bush before the commencement of the project. The unique biodiversity of our coastal flora and fauna was under significant threat.

This led to the following statement by Rod Ensbey, the regional weed control coordinator for NSW Agriculture:

“A long-term integrated control program is being implemented to combat this weed threat. This involves a combination of manual, biological and chemical means to control this problem.”

The sheer scale of the Bitou Bush threat ruled out manual methods as the main form of control.

And, while Ensbey noted that Australian researchers are investigating the potential of biological controls for Bitou Bush, these were at best going to be a useful backup tool.

A combined slashing/mulching option was carried out at Brunswick Heads, where the relative flatness of the terrain enabled suitable machinery to be used, and where the infestation of Bitou was so extensive that there was little native vegetation left to injure. The dead Bitou was used as a land-stabilising mulch, through which new plantings are now growing.

This left chemical means, however, as the principal method for the initial stages of the project.

The chemical chosen was glyphosate, a pesticide of “relatively low toxicity” and “moderate persistence”, according to toxipedia.com. In formulations such as Roundup, its toxicity is considered by some researchers to be increased somewhat by its combination with other otherwise harmless surfactants.

Byron council took three steps to minimise the impact of the use of Roundup on residents and the environment:

• Unlike in other shires, backpack spraying was undertaken, rather than aerial spraying.
• Spraying was undertaken in winter when substantially lower doses of the chemical are required.
• Council made use of its “opt-in” list of chemically sensitive residents, to ensure those who had registered their concern were informed well in advance of any spraying in their area.

Finally, the use of spraying enabled other serious weeds to be simultaneously targeted. Some of these weeds, such as Glory Lily, are themselves toxic to humans and so cannot safely be tackled manually.

Battle of the Bitou

But the war must go on, say regenerators

Byron Shire Council is claiming victory in its recent battle with the invasive coastal weed, Bitou Bush. Council workers and contractors, backed up by local Dune Care groups, have been targeting the noxious vegetation in a three-year campaign to oust it from our dunes.

It is the first step in a major reclamation of some of our most fragile foreshore, funded by the NSW State Government’s Environmental Trust.

Eight sites were selected for the project, comprising almost seven kilometres - or 40 percent - of council-controlled beachfront.

“[Bitou Bush] crowds out wattle and banksias,” explains Byron’s Bush Regeneration Team Supervisor Heidi Lunn.

“At some of our sites, like Broken Head, it was going right through the rainforest and getting up really high into the big trees, breaking off branches. So it is a really big threat.”

Byron Shire had the worst remaining infestation of Bitou Bush in the state, after Tweed and Ballina Shires eradicated significant amounts through aerial spraying of herbicides over the past few years.

But the proximity of local residents to the shire’s Bitou infested areas, and a groundswell of local opposition to aerial spraying, required a more considered approach from Byron Council.

Several techniques were trialled, including mechanical mulching of Bitou on flat sand at Brunswick Heads. But in many areas, due to heavy slopes or the need to preserve native species, targeted overspraying was the only viable method.

This involved council staff and contractors literally going bush-to-bush with knapsack sprays.

“Council took steps to minimise the impact of spray on local residents,” says Byron’s Natural Resources Team Leader Scott Hetherington.

“Trained contractors and council workers undertook the spraying during winter, when considerably less poison is needed.”

“In addition, Council activated its register of residents with a high sensitivity to herbicides, ensuring that those affected by a particular program were advised well in advance.”

Admittedly, not everyone was pleased to see the “regen” teams with their backpack sprays.

Heidi recalls: “At one site someone drove past and stuck their finger up at us and beeped the horn - but other than that it’s been mostly positive. We’ve had people applauding us as they walk to the beach when they see us spraying the Bitou. I guess it all depends on how much awareness they have [of the danger it poses].”

The program has also impacted on other weed species.

 “A lot of the sites don’t just have Bitou, they’ve got other weeds, like Coastal Morning Glory - or Madeira Vine- and Glory Lily,” explains Heidi.

“[Because of the on-ground approach] we were able to target some of those other weeds as well.”

With the spraying now mostly out of the way, the teams are undertaking the more rewarding task of replanting areas once dominated by Bitou.

On April 22, the council’s team planted some 50 littoral rainforest species on a strip of coastal land at Brunswick Heads. Until recently it had been colonised by Bitou.

Council workers and Dune Care volunteers are undertaking similar plantings at all eight sites up and down the coast.

Brunswick Dune Care volunteer co-ordinator Michael Maloney is optimistic about the project. But he also has some concerns for the future. And with good reason: Bitou seeds can remain viable in the sand for up to seven years.

“Regular maintenance is very important. You can get the funding for the primary work and planting - but regular upkeep and maintenance doesn’t seem to be as pretty in the eyes of governments,” says Michael.

We’ve achieved a lot but we’ve still a lot to do. It’s not finished yet.”

[Story and photos by Chris Dobney]