Five years after a severe bushfire nearly wiped out a quokka population near Northcliffe in Western Australia, research indicates they may not fully recover until 2028.
The World Wide Fund for Nature-Australia (WWF-Australia) says this has implications for the review of Australia’s flagship environment law, the Environment Protection and Biodiversity Conservation (EPBC) Act.
When flames charred 98,000 hectares of forest near Northcliffe in 2015, it was estimated the area was home to 594 quokkas.
Twelve months later, it was estimated only 39 of the small wallabies remained in the core of the fire area.
After the latest surveys, scientists estimate 272 quokkas are now within the bushfire-affected area. This recovery has been helped by increased efforts by the Western Australian Department of Biodiversity, Conservation and Attractions (DBCA) to control introduced fox numbers in and around the fire scar at a time when quokkas are most vulnerable.
Quokkas spotted on sensor cameras during surveys of bushfire-effected area near Northcliffe
In five years, quokkas have recovered to about 46% of their pre-fire population. However, projections suggest that it may take until 2028 for quokkas to return to their pre-fire numbers and distribution within the Northcliffe fire area.
Another major blaze or any other disturbance that increases the fragmentation of suitable habitat patches could set back that timeline.
WWF-Australia has partnered with DBCA to research the impact of the 2015 bushfire on quokkas.
“The quokka project has shown us for the first time just how long it takes for a population to recover after a large bushfire event. We estimate it may take 13 years in total for the Northcliffe quokkas to again number 600,” said WWF-Australia Species Consultant in WA, Ashleigh Chauvin.
“Quokkas face the same threats as many other threatened species: habitat fragmentation, feral predators, and droughts and bushfires made worse by climate change.
“One bushfire can wipe out a whole population of any species. We need to retain as much habitat as possible and create linkages between habitat patches so some animals can escape.
“It’s crucial the review of the EPBC Act strengthens protection of remaining habitat. And that key learnings from this project help inform the response to Australia’s 2019-20 bushfire crisis,” she said.
Other findings from the Quokka Project
• Recolonising quokkas preferentially occupied habitats with a complex vegetation structure and a sedge-dominated understorey.
• This helps the quokkas to regulate their body temperature and to escape predators such as the introduced fox and feral cats.
• In the first year post fire, quokkas were found a maximum distance of 186 m from unburnt canopy (average 12.5 m).
• Canopy damage was a significant predictor of the time taken for sites to become occupied by quokkas:
o Sites that contained a mix of scorched and unburnt canopy were on average occupied by quokkas within 2.8 years.
o Sites where the canopy had been completely scorched were on average occupied within 3.8 years.
o Sites where the canopy had been defoliated had a low occupancy rate, but where they were occupied this had taken an average of 4.7 years.
• In 5 years, quokkas have moved more than 50 km to recolonize some patches of habitat, and now occupy 59% of sites where they were known to live prior to the bushfire.
• The wallowing and digging behaviours of feral pigs contributed to areas of altered soil structure, physical disturbance of vegetation that was recovering from the fire, and removal of seedlings, seed and lignotubers.
• Quokkas avoided areas of habitat that had been significantly damaged by pigs, possibly because these areas were more accessible to introduced predators and provided lower quality shelter.