Recent research by CSIRO, Australia’s national science agency, shows that climate change has driven a ‘significant increase’ in Australia’s forest fire activity over the last three decades.
A lengthening of the fire season towards Autumn and Winter were also identified, along with an increase in fire activity in cooler and warmer regions including alpine forests in Tasmania and tropical rainforests in Queensland.
This is not really ‘new’ news. The impacts of climate change in terms of length of fire season and intensity of fire is well documented (for instance, the head of the firefighting agency for Victoria’s public lands, Chris Hardman, notes that there has been a 170% increase in bushfire ignitions over the last 50 years, a 20% reduction in spring rainfall, and a 40% increase in very high and severe fire risk days.
What is especially interesting is that this research, which was published in Nature Communications is the first of its kind in that it combines analysis of previous forest fire sites with eight ‘drivers’ of fire activity including climate, fuel accumulation, ignition and management (prescribed burning).
Reporting in The Age noted that:
The CSIRO report found other factors have an impact on the extent and intensity of bushfires such as the amount of vegetation or fuel load in a forest, the time elapsed since the last fire, and hazard reduction burning. But Dr Canadell said the study showed the link between weather and climate conditions and the size of bushfires was so tight, it was clear these factors far outweighed all other fire drivers.
In other words, ‘Climate’ trumps all other factors, including ‘fuel reduction’. This has significant implications for how we manage landscapes and fight fires.
Thirty-two years of satellite data and 90 years of ground-based datasets from climate and weather observations, and simulated fuel loads for Australian forests, formed the basis of the research, which allowed researchers to identify climate change driven increases versus natural variability.
CSIRO scientist, Dr Pep Canadell, said the research was one of the most extensive studies of its kind performed to date, and was important for understanding how continued changes to the climate might impact future fire activity.
“While all eight drivers of fire-activity played varying roles in influencing forest fires, climate was the overwhelming factor driving fire-activity,” Dr Canadell said.
“The results also suggest the frequency of forest megafires are likely to continue under future projected climate change.”
Over the last 90 years, three of the four mega fire years occurred after the year 2000. A mega fire year is defined as the cumulative burned area of forest over one year of more than 1 million hectares. (Fires greater than 100,000 hectares have also been increasing – check this list for details).
When comparing the first half (1988 – 2001) with the second half (2002-2018) of the record studied, the research showed that the average annual forest burned area in Australia increased 350 per cent, and 800 per cent when including 2019.
Comparing the same time period, the research showed a five-fold increase in annual average burned area in winter and a three-fold increase in Autumn, with Spring and Summer seeing a ten-fold increase.
“In Australia, fire frequency has increased rapidly in some areas and there are now regions in the southeast and south with fire intervals shorter than 20 years. This is significant because it means some types of vegetation won’t reach maturity and this could put ecosystems at risk,” Dr Canadell said.
“Understanding these trends will help to inform emergency management, health, infrastructure, natural resource management and conservation.”
What must we do?
Australia’s mean temperature has increased by 1.4 degrees Celsius since 1910, with a rapid increase in extreme heat events, while rainfall has declined in the southern and eastern regions of the continent. Globally fire activity is decreasing, however, the extent of forest fires in Australia is increasing.
Using climate change terminology, we need to both ‘mitigate’ (reduce greenhouse gas emissions) and ‘adapt’ to changed conditions that will come from the climate change that is already locked into the system.
In terms of mitigation, please check our Act on Climate and Yes 2 Renewables campaigns for ideas on taking action.
In terms of adaptation, here are some ideas:
Build our fire fighting capacity
Remote area firefighting. It’s great that the Victorian government has invested in more career firefighters. We need to also establish a remote area firefighting team responsible for tackling fires in our national parks and state forests. NSW, Tasmania and the ACT already have volunteer units. Victoria should do the same.
A national, publicly owned air fleet. One of the recommendations of the recent Bushfire Royal Commission report recommends the creation of a national publicly-owned aerial firefighting fleet, which can then be allocated to the states “according to greatest national need”. The federal government has refused to adopt this recommendation.
To add your voice to the call for a national air fleet, please check here.
For background information on fires and the need for a fleet, please check here.
For other ideas on building our capacity to fight fire please check here.
Impacts on mountain Environments
The report notes that
In addition, we find that the frequency of megafire years in forests with more than 10,000 km2 (1M ha) burned has markedly increased since 2000. Together these trends have led to the rapid decrease in the number of years since the last fire.
A continuation of that trend, especially in areas with sensitive species, could lead to significant ecological changes. Examples of sensitive ecosystems are the mountain ash (Eucalyptus regnans) and alpine ash (Eucalyptus delegatensis) forests in Victoria. Both species are obligate seeders that require 20-30 years to reach maturity and begin to establish a seedbank able to recover the forest after fire. Some regions show average fire frequency of about 20 years or less for the last decade. At this short fire return interval, if fires were to be of high severity leading to tree mortality (which this study has not assessed), both ecosystem-types would be at risk of local collapse.
Check the Alpine Ash tag in the main Mountain Journal menu for a huge number of stories about Alpine Ash and fire.