Deliberate burning of rare native habitat may provide a critical key to reviving the fortunes of the endangered Purple Copper Butterfly (Paralucia spinifera).
With that end in mind an experimental ‘cool burn’ of Native Blackthorn (Bursaria spinose ssp. Lasiophylla) has just been coordinated by Central Tablelands Local Land Services on a property at Mount David, between Black Springs and Burraga, south of Bathurst.
According to the Office of Environment & Heritage, the Purple Copper Butterfly has been found on just 29 isolated sites of remnant native vegetation over a total area of less than 30 hectares.
Researchers are hoping the use of low temperature burning (conducted under the provisions of an S91 Permit issued through the Office of Environment and Heritage) will promote new growth of Native Blackthorn bush, which is the primary food source for butterfly larvae.
“We have conducted ten trial burns, each over a patch of just 5 metres by 5 metres, in an area of Native Blackthorn on property owned by Rod and Alexandra Tuson,” explained Allan Wray from Central Tablelands Local Land Services.
“We have started with quite small burns as we want to make sure we have solid evidence the technique is beneficial before we use fire over a wider area.”
Rod and Alexandra Tuson discovered the rare Purple Copper Butterfly on their property in 2002. They now have a Voluntary Conservation Agreement in place over almost 69 hectares to protect butterfly habitat.
“In a farming landscape that has been cleared and fertilised for food production, it is important that some areas are set aside to generate the environmental services provided by native vegetation, and for the joy of wild places,” said Alexandra.
After a period of drought the Tusons noticed the population size of the butterflies had diminished and there was little new growth on the Native Blackthorn bushes.
“A very snowy winter in 2015 followed by a very wet winter in 2016 showed a further steep decline in the numbers of butterflies sighted,” said Alexandra.
“Caterpillar counts confirmed this so a project to rejuvenate Native Blackthorn was set in motion with a research design by Dr Milton Lewis from Local Land Services.”
The aim of the cool ecological burning technique is to promote the regrowth of Native Blackthorn and to reduce competition from grasses and weeds.
The low temperature fire burns singe the mature bush without destroying the plant, prompting new soft leaf growth which is particularly appealing to the young caterpillars.
“A secondary benefit of controlled prescribed burns is a reduction in the threat of unmanaged hot fires,” said Allan Wray. “Burning in winter at low temperatures also ensures that the caterpillar pupae are safely underground protected from the heat.”
“However during this trial phase we have avoided burning any clumps of Native Blackthorn where the butterfly larvae have been recorded over the previous season.”
Central Tablelands Local Land Services greatly appreciates the generous cooperation of the Tuson family for allowing the trial burn to take place on their property.
“We would also like to thank the Glanmire and Burraga Rural Fire Service crews who were on hand to ensure the burns were kept safely under control,” said Allan.
Post burn monitoring will now be undertaken on the trial sites in addition to the regular caterpillar count monitoring that takes place in December when the caterpillars hatch and begin feeding on bursaria.
For more information about the Purple Copper Butterfly and advice on how to enhance native vegetation and remnant habitat, contact Allan Wray at Central Tablelands Local Land Services on 02 6333 2318.