Science says regrowth after clearfell logging increases bushfire risk.
Professor David Lindenmayer
Professor David Lindenmayer, expert in Forest Wildlife Management and Nature Conservation, co-authored a research paper in 2009 ‘Effects of logging on fire regimes in moist forests’. This paper is a review of research from around the world, and indicates that logging practices elevate bushfire risks in wet forests.
The introduction states that the motivation for the study was in part to counter claims made by pro-logging groups (after the 2009 Black Saturday fires) for more logging to reduce bushfire risk.
Contrary to claims by some commentators (e.g., National Association of Forest Industries), industrial logging is likely to make some kinds of forests more, not less, prone to an increased probability of ignition and increased fire severity and/or fire frequency.
The media covered the release of Professor Lindenmayer's research report.
See Canberra Times news
See ABC news
Professor Ross Bradstock.
Probability of crown bushfire increased by logging regrowth.
During the Bushfire Royal Commission, Professor Ross Bradstock, Director of the Centre for Environmental Risk Management of Bushfires at the University of Woollongong, presented a research report (by himself and Owen Price) and spoke at the Commission as an expert witness.
What is crown bushfire?
Crown bushfire occurs when the tree canopy is burnt. The tops of trees a left defoliated after the fire. In contrast, crown scorch is when intense radiant heat from an understory bushfire kills the canopy leaves but they do not combust. Crown scorch creates a browned off canopy after the fire. Dead leaves eventually drop to the ground.
Crown bushfires are impossible to directly control as they significantly increase the overall energy level (radiant heat) of the bushfire. Crown bushfires and are a major cause of bushfire spotting. Bushfire spotting is when embers are picked up by wind and carried large distances to start new bushfires ahead of the main fire front.
Click download 4MB version
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Research on logging regrowth crown bushfires.
Bradstock’s and Price research (download pdf) was based on a statistical analysis of 4,500 points within forested public land that was burnt by fires started on Black Saturday. Bradstock found that weather was the driving influence on bushfire, followed by forest type and then fuel loads. All these factors are interrelated.
Professor Bradstock provided a presentation (download pdf) to the Bushfire Royal Commission that included an explanation on how young regrowth from past clearfell logged native forest, increases the crown bushfire risk.
“It appears that recent logging elevates the severity of fires. So you have got higher severity. We are talking about crown fires here" Transcript, 18 February 2010 Bushfire Royal Commission.
The following photos were taken during a field trip Toolangi State forest area, (Murrindindi fire complex) that support Professor Bradstock's research findings.
Click photo to download 4mb version. Photos taken on the 29th March 2009.
 1996 logging regrowth (coupe 08/299/979/0023) was crown burnt RHS of picture. Mature forest LHS did not crown burn. |
 2001 logging regrowth (coupe 08/307/002/0022) was crown burnt in foreground. Mature forest in background did not crown burn. |
Extract from Professor Bradstock's presentation to the Bushfire Royal Commission:
Professor Bradstock listed the order of influence on bushfire severity and intensity. The time since logging was not a dominate influnce, but never the less a significant influence. The results are counter intuitive.
Extract from Professor Bradstock's presentation to the Bushfire Royal Commission:
(Note TS = Time Since and Topo = Topological.)
Bushfire intensity mapping
Logging regrowth that established before the Black Saturday fires in the Toolangi State forest can be seen
using Google Earth (download kmz). The blue lines trace the boundaries of previous clearfell logging regrowth.
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 From DSE Forest Explorer, purple represents areas previously clearfell logged. |
Bushfire intensity maps (download 5 MB pdf) show the intensity of a bushfire. When logging coupes (blue lines) are shown on a
Murrindindi bushfire intensity map, most areas previously clearfell logged were crown burnt.
This supports Professor Bradstock's research findings.
Note: Other factors also influenced where forest was crown burnt.
Davd B Lindenmayer, Malcolm Hunter, Philip J Burton, Philips Gibbons, ‘Effects of logging on fire regimes in moist forests’ (2009) 2 Conservation Letters 271.
Bushfire Royal Commission Exhibit EXP-025-001-001. Fire Severity Patterns in the Victorian Fires of February 7th 2009: influences of weather, terrain and land use history: Ross Bradstock and Owen Price
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