This document summarizes a study quantifying the flammability of rainforests compared to Eucalyptus forests. The study examined fuel characteristics, microclimate conditions, and fire behavior in different forest types. Key findings include: 1) Rainforests have less fuel mass and burn more slowly than Eucalyptus forests. 2) Rainforest fuel moisture is less sensitive to diurnal changes than Eucalyptus forests. 3) Wildfire seasons in the region are starting earlier than 50 years ago, and climate change may increase rainforest fire risk by affecting fuel accumulation. The study provides improved understanding of rainforest fire behavior to inform predictive modeling and risk planning.
2. › How flammable are rainforests
compared to Eucalyptus forests
› What are their fuel characteristics
› Is the fuel micro-climate different
› Is climate change relevant
› How will fires behave in rainforests
› How will species respond after fire
› Can we improve our predictive
capabilities and risk planning using
this information
Study objectives
Ecotone forests are utilised by a range of
threatened fauna – Tiger Quoll.
4. Is the climate changing?
500
1000
1500
2000
2500
3000
3500
1962
1963
1964
1965
1966
1967
2009
2010
2011
2012
2013
2014
2015
2016
rainfall (mm/year)
litterfall (kg/ha/year)
Rainforest litter inputs are
correlated with annual
rainfall
5. Rainforest fires in northern NSW
Hazard reduction burn wet sclerophyll – rainforest
interface northern NSW. Photograph Dale McLean
› Frequency of 1-2 per century per
stand;
› Significant wildfires burnt
rainforest in 1915, 1918, 1956,
1968, 1996, 2012 and 2013
› Conglomerate Coffs Harbour
wildfire of 1968 ‘Even rainforests
were burning’ (Humphreys 2012)
› Do we need to be become more
proactive in managing risk?
6. Macleay River wildfire Oct 2012
burnt significant area of dry rainforest
in Oxley Wild Rivers NP
7. Are the north coast wildfire seasons changing?
0
100
200
300
400
500
600
700
800
Total number of fires per month
1951 - 1961 (n=2905)
2002 - 2016 (n=2911)
0
5
10
15
20
25
30
35
40
45
50
% of region burnt per month
1951 - 1961
2002 - 2016
16. Fine fuel inputs in rainforest are strongly seasonalJanuaryFebruary
M
arch
April
M
ay
June
July
AugustSeptem
ber
O
ctoberN
ovem
berD
ecem
ber
litterfallkg/ha-1
/month-1
0
20
40
60
80
100
120
› Spring is the peak season for
litter fall
› Spring is the peak season for
wildfire ignitions
› In spring fuels are generally at
their lowest seasonal fuel
moisture content
› In spring ambient humidity is
low.
17. Fine and coarse rainforest fuel inputs increase in wetter
years
350030002500200015001000
2800
2600
2400
2200
2000
1800
1600
1400
1200
rainfall (mm/year)
litterfall(kg/ha/year)
Fine fuels < 6mm
R² = 0.9779
0
100
200
300
400
500
600
700
800
900
1000 1500 2000 2500 3000
kg/ha-1/yr-1
sampling period annual rainfall (mm)
Coarse fuels > 6mm
29. Large tree size class most
likely to ignite and fall
tree DBH (cm)
10-19.9 20-29.9 30-39.9 40-49.9 50-59.9 60-69.9 70-79.9 80-89.9 90 +
proportionoftreesburnt
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
30. Changes in fine fuel
biomass following HRB,
wildfire and canopy
scorch
WSF Shrubby forests
Cool Temperate Rainforests
36. Outcomes
› How flammable are rainforests compared
to Eucalyptus forests
› What are rainforest fuel characteristics
› Is climate change relevant
› Is the fuel micro-climate different
› How will fires behave in rainforests
› How will species respond after fire
› Can we improve our predictive capabilities
and risk planning using this information
› Lower ROS, heat output, ignitability, mass loss
etc
› Less mass, depth, elevated fuels, increased
FMC and bulk density
› Wildfire seasons are earlier than 50 years
ago, rainforest fuel mass increases in wet and
cool years and is at seasonal max. in spring.
› Rainforest fuels less sensitive to diurnal RH
variation than Eucalyptus forests. Importance
of antecedent soil drying.
› Rainforests are anti-flammable. Large tree
mortality and dieback, understorey re-
sprouting
› Yes if we strategically address risks to
environmental assets through BFRMP’s
37. Outreach outcomes
› A sustainable model for citizen science
volunteering in fuel and climate
monitoring has been established
