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Leadbeaters beat a path to logged and burnt forests

Leadbeater’s Possum, officially designated as ‘critically endangered’, has been detected in a recently burnt and logged forest further east from its main habitat area, according to a peer-reviewed study. The study, published by the CSIRO in ‘Australian Mammology’ earlier this year, used remote camera and spotlight surveys at six locations up to 15 kilometres from the possum’s prescribed range in the Central Highlands of Victoria. Source: Philip Hopkins for Timberbiz

Half the records occurred in fire-affected, mixed-species forest that differs markedly from the possum’s predominant habitat, which is late-mature forests dominated by mountain ash, alpine ash and shining gum.

The peer-reviewed study was conducted by two VicForests scientists and environmental consultants Ecology and Heritage Partners in an area where the Goulburn and Thomson River Basins meet.  It comes after surveys led by the Arthur Rylah Institute have found thousands of Leadbeater’s Possum in forest within its core range.

The possum’s ‘critically endangered’ status has prompted environmentalists to demand a Great Forest National Park to save the species, which would destroy much of Victoria’s native forest timber industry.

The study, based on two three-monthly surveys, found Leadbeater’s possums at six independent sites 1-14.8 kilometres outside their prescribed range and 3.6-14.2 kilometres from the next nearest observation points.

“This represents a notable extension in the eastern distribution of the species,” the authors said.

Detections occurred in both mixed-species and ash-dominant forest regenerating after the Southern Great Divide fire (2006-07) and ash-dominant forest regrowing after timber harvesting.

“These findings are particularly significant because Leadbeater’s possums are considered highly susceptible to fire impacts and have small home ranges,” the authors said.

The detections in recently disturbed forest followed the same pattern as those found in the young regrowth forests in the Arthur Rylah surveys.

“Additionally, our sites were located in forests within 1-15km of the south-eastern boundary of the Great Divide Complex bushfire, which burned more than 1 million ha over two months from December 2006,” the authors said. “One site near Mount Useful is surrounded by forest repeatedly burned.”

These finding suggested the possum could traverse a disturbed forest and re-colonise fire-affected habitat within a decade of a severe bushfire, and/or could survive in low burned or unburned refuge areas.

“This is supported by the number of post-fire records of Leadbeater’s possum in forests more than 2km from the boundary of the 2009 Black Saturday fires,” the authors said.

“Conventional models predict low to zero probability of …. Leadbeater’s possum in burned forests within 15 years after fire.”

These models were based on observations within three years of fire. They assumed possums could not move more than 2km through disturbed forest and that suitable foraging and nesting habitat do not occur until 15-150 years after fire, the authors said.

Three of the peer-reviewed study’s records were in mixed-species forest regenerating from fire. The authors said if viable possum populations lived in mixed forests, their risk of extinctions from fire would likely be reduced.

This was because mixed-species eucalypts were more fire-tolerant, re-sprouting trees compared with their ash counterparts, “which are fire-sensitive obligate seeders prone to stand reinitiation after several wildfires”.

The authors said potentially suitable possum habitat was extensive both within and east of the possum’s core range.

“Priority should be placed on surveys to determine the status, distribution and population dynamics of Leadbeater’s possum across this landscape, especially within the substantial areas of mixed-species and fire-affected forests,” the authors said.

Since 2014, investigation had concentrated on unburned, ash-dominant forest within the possum’s known distribution range.

“Consequently, management of mixed-species State Forest and Park areas for timber harvesting, recreation, road-building and fuel-reduction burns has been conducted under the assumption that Leadbeater’s possum is not present, or is not likely to be impacted by these activities,” the authors said.

“Timely integration of research findings will advance conservation research and planning for Leadbeater’s possum and support evidence-based forest management.”