Bushfires, which were started by lightning strikes, burnt large areas of Tasmania last summer.
There have been fears expressed by ecologists that large areas of fire sensitive vegetation have been impacted.
An initial desk top assessment carried out by researchers at the University of Tasmania suggested that the areas of these vegetation types affected was very small.
In March, the Tasmanian Parks and Wildlife Service updated their assessment, which also stated that only small areas of vegetation types that are rated ‘Extreme fire sensitive’ (containing components that will not recover from fire, such as rainforest with king billy pine, alpine conifer communities, alpine deciduous beech communities and rainforest with deciduous beech) and ‘very High fire sensitive’ communities (including alpine and subalpine heathland without conifers, rainforest without conifers, and mixed forest) had been affected.
Now, an additional assessment, by the Tasmanian National Parks Association (TNPA), adds further detail to our understanding of the impacts of this summer’s fires.
This comes from the report ‘Summary of 2018-19 Tasmanian fire season’ produced by the TNPA.
This assessments provides extra detail about the areas that were badly impacted, including old growth eucalyptus forests. Some additional points to consider:
- The extra detail in this report suggests that a larger area of fire sensitive vegetation has been impacted than previously thought
- This fire event did not happen in isolation. There were significant fires in 2013 and 2016 fires, each causing damage to fire sensitive communities. Because of the incredibly long time frame for these vegetation types to recover, each year’s fire needs to be seen as being linked events in terms of understanding the cumulative ecological impacts of fire
- Climate change is expected to make fires worse
“The bland statistics downplay the real-world impact; they note that “only 3.2%” of the area burnt is rainforest but this is still some 6000 ha that will likely take many centuries to recover.
And alpine country is not distinguished in the vegetation community classification used but is known to have been burnt in some areas (Crest Range, Denison Range, Central Plateau) and possibly others (Schnells Ridge, Eastern and Western Arthurs)”.
REPORT: The extent of areas burnt by the 2018-19 wildfires and impact on natural values
According to the Tasmanian Fire Service (TFS) mapping, the total burnt area is some 205,000 ha. Hardly any cleared agricultural land was burned, it was predominantly native vegetation and some forestry plantations, illustrated by this map. This was the largest land area burnt since the devastating Black Tuesday fires in 1967 and comprises 3.2% of the state’s total mainland area. Almost half of this (about 93,000 ha) is within the TWWHA. This comprises 5.9% of the TWWHA. (And remember that 45,000 ha also burnt in 2013, and then there were the 2016 fires, so about 10% of the TWWHA has been burnt in 6 years.)
Here is a first attempt at analysing what has been burnt, by the University of Tasmania’s Fire Centre Research Hub. The bland statistics downplay the real-world impact; they note that “only 3.2%” of the area burnt is rainforest but this is still some 6000 ha that will likely take many centuries to recover. And alpine country is not distinguished in the vegetation community classification used but is known to have been burnt in some areas (Crest Range, Denison Range, Central Plateau) and possibly others (Schnells Ridge, Eastern and Western Arthurs); see below. And there is inevitable heterogeneity even within areas mapped as vegetation communities “resilient to fire”, with the landscape including copses and corridors of more sensitive vegetation.
Furthermore, some areas were also burnt in the 2007 wildfires so incremental loss of organic soil (peat) in these areas, and on better-drained slopes, is likely. On the basis of our own analysis undertaken in mid February, using TFS and other public data, the vegetation considered “extreme” or “very high” fire sensitivity1comprises just over 3% of the total statewide burned area. This doesn’t sound like much but is potentially pretty significant given the large total area burnt.
Media-reported commentary by PWS and others often seemed to downplay the potential or actual impacts of the fires on natural values. Reporting of the natural values at risk was largely down to groups like ourselves, Nature Photographers Tasmania and the Wilderness Society Tasmania; for example, see here and here. Maps prepared by PWS on 15th February and made available to stakeholders like ourselves somewhat later indicated that some 479 ha of “fire sensitive threatened” vegetation communities had been impacted by the fire at that time. But threatened is used here in a strict biodiversity conservation sense and the somewhat reductionist approach therefore does not include widespread fire sensitive communities like alpine heathland or some rainforest types. The mapping also indicated that some 16,800 ha of “old growth forest” had been impacted in some way. Preliminary fire severity mapping indicated 7,061 ha of Eucalyptus regnans forest (677 ha in the TWWHA) had been impacted, with an overall 25% of this considered impacted at high or very high severity. More detailed fire severity mapping has not yet been reported) and will be required before the overall damage is clear.
“The mapping also indicated that some 16,800 ha of “old growth forest” had been impacted in some way. With an overall 25% of this considered impacted at high or very high severity”.
In Parliamentary questioning following his State of the State address in late March, the Premier and Parks’ Minister finally acknowledged the extent of damage to the TWWHA, noting that 6% of its area had been burnt and that 16% of this was not “fire adapted” and, by implication, unlikely to recover. Outside of the TWWHA, a post-fire survey has shown that fifteen of Australia’s listed tallest or biggest trees, >85 metres tall or >280 cubic metres in volume, and so up to 500 years old, were destroyed by the Riveaux Road (Huon Valley) fire. The age of these trees perhaps gives an indication of how long since parts of these forests were last burnt by a fire as intense as last summer. It is unlikely to be as long until the next one.
[IMAGE: Grant Dixon. Steep burnt ridges at the northern end of the Eastern Arthur Range, Federation Peak beyond. These tongues have burnt right up to the range’s alpine zone.]
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