This presentation by Andy Baker discusses how fire-exclusion threatens the vast majority of Byron Shire’s fire-dependent vegetation and is likely to result in irreversible vegetation change and habitat loss unless fire is restored across the landscape.
Presentation from Nature Conservation Council of NSW 2015 Bushfire Conference - Fire and Restoration: working with fire for healthy lands.
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BushfireConf 2015 - 5. Where has all the fire gone? Quantifying the spatial and temporal extent of fire exclusion in Byron Shire NSW
1. WHERE HAS ALL THE FIRE GONE?
Quantifying the spatial and
temporal extent of fire exclusion in
Byron Shire NSW
Andy Baker
Wildsite Ecological Services
2. Overview
Fire Exclusion & Vegetation Change
GIS Analysis Methods
Results - Fire exclusion in Byron Shire
3. 3 Key Messages
1. Nearly half of Byron Shire’s biodiversity needs
regular fire to maintain suitable habitat
4. 2. Without regular fire,
habitats can change rapidly
3. If habitat becomes unsuitable,
localised extinctions follow
5. Fire Exclusion & Vegetation Change
• Worldwide phenomenon
• Two main processes:
1. Treeless ecosystems forests
2. Open forest rainforest
6. Wet Tropics Bioregion
• 25% (>100 000 ha.) open forest/woodland
rainforest since 1950’s
• 2014 study mapped 2 million ha.
(Stanton et al. 2014)
Major open forest types
18. Open Forests Rainforests
Fire-resistance
threshold
• Rainforest trees not removed by fire (manual removal?)
• Rainforest regrowth quickly resumes transition process after fire
21. METHODS - GIS Analysis
Native
Vegetation
Endangered
Ecological
Communities
Coastal
Wetlands
Coastal Koala
Habitat
Time since
last known fire
Fire Exclusion
Status
Fire-intervals
guidelines for
vegetation types
27. Step 5: Assign recommended
fire intervals
• Specific to the region
• Recommended by Northern
Rivers Regional Biodiversity
Management Plan (DECC 2010)
• Factor in risk of
vegetation change resulting
from fire exclusion
28. Fire Interval Guidelines - NSW North Coast and SE Queensland
compiled from Watson 2001, Watson 2006 and Tierney & Watson 2009
34. Long-term Fire Exclusion
across
Key Conservation Values
RESULTS
Coastal Koala Habitat
All koala feed trees require fire for widespread recruitment
35. So what is their relative importance in Byron Shire?
High vs Low Frequency Fire
High Frequency Fire
o listed as Key Threatening Process (TSC Act)
o routinely listed as a threat in ecological assessments
Low Frequency Fire
o Not listed as KTP
o Rarely considered in ecological assessments
Inappropriate Fire Frequency
What about high frequency fire?
36. Fire-exclusion is spatialy extensive…
but by how long are thresholds exceeded?
Temporal Extent
?
No
Data
species &
habitat
decline
10 yrs
41. Conclusion
Fire exclusion:
• major threatening process affecting Byron Shire’s biodiversity
• potentially widespread in similar regions along east coast
Restoration complicated by:
• encroaching trees that have become fire resistant, and
• loss of flammable understorey to carry ecological burns
Further research:
• What is the extent of fire-exclusion in other regions?
• How quickly are critical thresholds reached in diff. ecosystems?
42. References
Beadle, N.C.W. and Costin, A.B. (1952) Ecological classification and nomenclature. Proceedings of
the Linnean Society of New South Wales 77: 61-82.
Stanton, P., Stanton, D., Stott, M. & Parsons, M. (2014) Fire exclusion and the changing landscape of
Queensland’s Wet Tropics Bioregion 1. The extent and pattern of transition. Australian
Forestry, 77, 51–57.
Tierney, D., & Watson, P. (2009). Fire and the Vegetation of the Namoi CMA. Nature Conservation
Council of NSW, Newtown.
Walker,J. & Hopkins,M.S.(1984). Vegetation. In R.C.McDonald, R.F.Isbell, J.G.Speight, J.Walker &
M.S.Hopkins(eds). Australian Soil and Land Survey Field Handbook. pp44-67. Inkata Press,
Melbourne.
Watson, P. (2001). The role and use of fire for biodiversity conservation in south-east Queensland:
Fire management guidelines derived from ecological research. Nature Conservation Council
of NSW, Newtown.
Watson, P. (2006). Fire frequency guidelines and the vegetation of the Northern Rivers
region. Nature Conservation Council of NSW, Newtown.
43. Read more...
Baker, A and Catterall, C. (2015) Where has all the fire gone?
Quantifying the spatial and temporal extent of fire
exclusion in Byron Shire, Australia. Ecological
Management & Restoration 16. doi: 10.1111/emr.12161
Ecological Management & Restoration
Volume 16, Issue 2, May 2015
Today I’ll present the findings of research looking at fire-exclusion on the far north coast of NSW, using Byron Shire as a case study
Firstly I’ll outline the process of fire exclusion and vegetation change
Outline the GIS analysis methods
And finally the results of the study
Firstly, 3 Key messages
Nearly half of Byron Shire’s biodiversity needs regular fire to maintain suitable habitat
Without regular fire – habitats can change rapidly
If habitat becomes unsuitable, localised extinctions follow
Vegetation change following long-term fire exclusion is a worldwide phenomenon and is well documented across all continents except Antarctica.
Vegetation change is frequently divided into two main processes including…
The transition of treeless ecosystems to forests, which is well documented for the savannas of northern Australia and the heathland’s of western and southern Australia.
And secondly, the transition of open forest to rainforest, which is well documented in higher rainfall areas such as Tasmania, the Sydney region and the Queensland Wet Tropics…
A 2014 study, which mapped c. 2M ha. of vegetation…
found that 25% of open forest & woodland has irreversibly transitioned to rainforest since 1950’s (>100 000 ha.)…
Of the region’s major open forest types, 3 have had more than 70% of their range captured by rainforest since the 1950s
And several types are now considered endangered due to extensive rainforest transition
So why is change happening?
This diagram represents the development of vegetation through time
On the NSW far North coast, high rainfall and mild temperatures allow vegetation to reach full development to rainforest, the region’s climatic potential
Vegetation is always moving toward this climatic potential of rainforest unless interrupted by disturbance
However in this region and throughout the world, fire deflects this development
and regular fire maintains the vegetation in a narrow state of development along the spectrum
Most importantly, it is fire interval that determines where along the spectrum vegetation is maintained
With a very short fire interval-say every five years– development may be arrested at the grassland stage
If fire interval is increased to around 20 years – dry sclerophyll forest may develop
If fire is excluded for 100 years or more – rainforest is likely
Those vegetation types that are maintained by a specific fire interval are termed fire-dependent
They are considered fire dependent not only because fire exclusion results in a shift to another vegetation type
But because virtually all species require fire for recruitment – and will only recruit after wholesale removal of biomass and baring of the ground surface by fire
Now let’s look at the process of forest encroachment into treeless ecosystems
This is a endangered heathland restricted to Byron Bay
In between fires, young trees may recruit into the heathland
Historically at about this time a fire would pass through the community removing all the young trees, restoring the original heathland structure
However in the continued absence of fire, trees continue to develop and if a fire passed through at this point many of the trees would survive
This represents passing of critical threshold making restoration of former structure with fire alone impossible
The trees continue to develop an overstorey above heathland, and shade-intolerant understorey plants begin to drop out of the community, as can be seen in the bare areas in the right of the photograph
Continued canopy development continues to suppress understorey vegetation causing a dramatic reduction in species diversity and a reduced ability of the community to carry fire
To show an example of this process from the air - this is an area of wet heathland in Brunswick Heads Nature Reserve
The fine-textured area within the orange line is treeless vegetation and beyond the line - forest and tall shrubland
Moving forward 30 years without fire to 2012 - forest and tall shrubland has displaced much of the heathland
Similar trends are found in most of Byron Shire of treeless ecosystems
Now let’s look at the transition from open forest to rainforest
This diagram represents a typical open forest structure, in particular note the diverse understorey dominated by flammable shrubs and grasses
In between fires, rainforest trees recruit into the understorey - this process can be rapid and widespread due to seed dispersal by birds & bats
Historically, at this stage a fire would pass through the community, removing the rainforest trees and restoring the typical open forest structure.
Without fire, rainforest trees continue to recruit & grow
Studies show that most rainforest tree species quickly reach an age where they can survive complete topkill from intense wildfires - this is known as the fire-resistance threshold
At this stage - rainforest trees are no longer removed by fire alone, but need manual removal to restore original structure, and rapid rainforest regrowth resumes the transition process quickly after fire
With ongoing fire exclusion, the developing rainforest midstorey begins to shade out the flammable understorey this is known as the fire-suppression threshold
At this stage the understorey is unlikely to carry fire (prescribed or wildfire) and the option for applying an ecological burn in safe weather conditions has been lost
And floristic diversity is lost from the understorey
So, is fire exclusion a problem in Byron Shire?
To determine this, GIS analysis was undertaken that compared time since last known fire with fire interval guidelines for mapped vegetation across the study area
These datasets were then combined to determine fire exclusion status across a range of key conservation values
Preparing fire records for analysis was a one step process that involved combining all fire records from the NPWS & RFS to produce a single layer showing all recorded fire events over the last 40 years
Mapping recommended fire intervals involved assigning fire interval recommendations to mapped vegetation across the study area
Step 1 involved combining vegetation datasets from the national parks and wildlife service, Byron Shire Council in the northern rivers catchment management authority into a single layer
Step 2 - involved identifying all areas of exotic vegetation (such as camphor laurel) and removing these from further analysis, leaving only native vegetation
Fore Step 3, Vegetation polygons were then assigned to one of six vegetation formations
Step 4 involved determining the fire relationships by reference to the literature
Fire dependent vegetation included all grasslands and sedgelands, heathland, all sclerophyll forest types
Fire sensitive vegetation included rainforest, mangroves and saltmarsh
Undetermined mostly included areas of mixed regrowth where there was insufficient data to determine the original vegetation type or fire relationship
The final step involved assigning fire intervals to each vegetation formation by reference to fire frequency guidelines
The 2006 guidelines of Penny Watson were used as they…
are regionally specific,
Recommended by the Northern Rivers Regional Biodiversity Management Plan
And they consider the risk of vegetation change resulting from fire-excusion
In the left column are the different vegetation formations while in the right-hand column are the recommended fire intervals given in years
while the first four formations have only simple ranges – WSF is divided by understorey composition
The recommendations for wet sclerophyll forest also have a two tiered fire interval including more frequent low intensity understorey fires and infrequent high-intensity canopy fires
The vegetation was coded with the maximum interval for the top four formations - and for wet sclerophyll forest, the maximum understorey interval was used
Finally, the understorey was not known for many areas of WSF - these areas were automatically classed as ‘of concern’ if they have no fire for more than 20 years – given that at least some areas with shrubby understorey were known to occur within this group
And this map shows the resulting distribution of recommended fire intervals across the study area
So, is fire exclusion a problem in Byron Shire?
Looking at all fire dependent veg across the study area – only 10% is within threshold – 61% is fire excluded – with the remainder classed as ‘of concern’
Again the ‘of concern’ class is known to contain areas beyond threshold, but exact extent can’t be determined
Looking at the individual vegetation formations - all grassland is beyond threshold – and all remaining formations are less than 20% within threshold
So looking now at fire dependent endangered ecological communities – only 15% are within thresholds
Importantly these are our highest conservation value vegetation communities and provide unique habitat to myriad threatened species
and looking at the individual endangered ecological communities a similar trend is evident
A similar extent of Coastal wetlands is fire-excluded
These wetlands range from open sedgelands to forested wetlands and again are important centres for threatened biodiversity
Again with coastal koala habitat only 16% is within threshold
Koala feed trees, mostly eucalypt species, all require fire to recruit and as time since fire grows longer, opportunities for the recruitment of overstorey feed trees are rapidly disappearing on many sites.
What about high frequency fire?
High Frequency Fire is listed as Key Threatening Process, and is routinely listed as a threat in ecological assessments
Conversely, Low Frequency Fire is not listed as a KTP, and almost never mentioned in ecological assessments
So what is their relative importance in Byron Shire…
As can be seen, high frequency fire is almost mythical in Byron Shire, comprising less than 1% of all areas affected by inappropriate fire frequency since 1974.
Fire exclusion is spatially extensive, but by how long are thresholds exceeded?
This graph shows the proportion of grassland as a function of time since the last fire
The maximum interval for grasslands is 10 years , the grey area is where most of this community should operate, and it is immediately beyond this point that species and habitat are predicted to decline
Yet the vast majority of grasslands are more than four times past threshold and the time since last fire for these areas is in fact unknown – further increasing the likelihood of localised species extinction and habitat change
As we can see large proportions of many communities are more than 2 or more time beyond threshold.
And finally I’d like to provide a quick overview of the impacts of fire exclusion on floristic diversity
A total of 942 flora species have been recorded for Byron Shire, of which 430 (or 46%) are restricted to fire dependent communities
So how is this diversity distributed across different vegetation strata?
This graph shows the proportion of all fire dependent species occurring within each height-class across all fire-dependent vegetation types
As can be seen 84% of species occur below 2m
And it is this lowest strata which is the first to be impacted by vegetation change and shading
So while a eucalypt forest may seem in good condition – even early rainforest development in the understorey may have already suppressed the vast majority of floristic diversity
So, is Byron Shire unique?
An OEH analysis using the thresholds Liz Kenny & Ross Bradstock 2004 reveal a similar pattern for both fire exclusion generally
And the relative importance of high frequency fire across the region
In conclusion the study demonstrates the operation of a major threatening process affecting Byron Shire’s biodiversity that has previously been little recognised.
The threat is potentially widespread in similar regions along east coast
Restoration of transitioned sites may be complicated by:
encroaching trees that have become fire resistant, and
loss of flammable understorey to carry ecological burns in safe weather
Further research is need to determine
What is the extent of fire-exclusion in other regions?
How quickly are critical thresholds reached in diff. ecosystems?
