We are increasingly susceptible to widespread fires when we look at the last 90 years of fire information
According to a comprehensive review of 90 years’ worth of fire data, climate change is driving more severe bushfires in Australia. The number of megafires in Australia has increased dramatically since 2000, with a greater area of land being torched and blazes occurring more frequently in the fall and winter seasons.
Even the milder La Niña years do not provide much relief – in fact, after La Niña years, fires tended to be more severe. The researchers from CSIRO’s Pep Canadell warn that we should expect another bad fire season in the summer of 2022/23.
The major findings
According to Canadell, there have always been massive fires in Australia’s history. However, since 2000, megafire seasons (when forests are burned over 1 million hectares / 2,471,053 acres) have increased dramatically.
A study published in Nature Communications showed that three of the four forest megafires that have occurred in Australia since 1930 have taken place since 2000. Further, since 2000, Australia has seen nine of its 11 biggest fire years, each burning more than 50 million hectares.
Researchers sought to understand how forest fires affect the ecosystems of Australian forests.
The fire dynamics in woody-dominated ecosystems are very different than those of grass-dominated ecosystems, this includes rangelands which dominate the landscape of Australia. The study concentrated on areas with 324,000 square kilometers / 131274.734 square miles of forests rich in biodiversity, mostly on the eastern side of Australia and some in the southwest.
According to their research, Australian forests have seen a 350 percent increase in burned areas over the period from 1988 to 2018– if the current Black Summer fires are included, that figure rises to 800%. The colder months offer no refuge either—since 1988, autumn wildfires have burnt three times more forest than previously, and winter flames have torched five times more.
This is a major departure from past decades where wildfires were prominent in the spring and summer seasons.
The study also revealed that forests are burning at a higher rate. There are now fewer years between fires in the country – fire is returning again and again. In the 1980s, there were 70 years on average between blazes in any specified region. The number was down to 39 years in the 2010s, with many areas experiencing fires as frequently as every 20 years or less.
Canadell explains that there are now regions in the south and southeast experiencing fire cycles of less than 20 years. These forests are largely made up of mountain ash or alpine ash, which do not resprout after a fire. This is a hazard because it prevents certain types of vegetation from reaching maturity and potentially threatens to collapse the local ecosystem.
Forests take at least 20 years to mature before they can create what researchers refer to as a seed bank in the soil, thus allowing them to regenerate out of those seeds after a fire.
Local ecosystem collapse is a multifaceted process, but the data reveals that if these high fire frequencies continue, the potential danger of such a collapse is increased, and climate change does not help matters.
This should be a major concern for personnel in the field of vegetation management, particularly controlled burning, to help assure that such species get the best possible shot at long-term survival.
The entire continent is affected
Australia’s fires don’t just stop with the forests either. Researchers found an increase in the total area burned throughout the whole of the continent, and wetter weather cycles like La Niña provide no reprieve.
In fact, the largest fire years are those following the wet weather cycles because the wetter weather increased the amount of plant growth making more fuels – biomass – readily available.
Australia is mostly covered with rangelands, which are characterized by plants such as spinifex that react swiftly to increased rainfall. They develop rapidly, before drying out the following year. While forests typically experience a decrease in fire activity during La Niña years, these rangeland ecosystems will be ready to burn due to the increase in biomass availability.
Canadell described that following the large 2010/11 La Niña, Australia saw likely its first 100-million-hectare fire season. That’s an area about four times the size of the UK. The fire burned through central Australia and continued for months
Researchers believe that a similar cycle is presently occurring.
Researchers warn of the need to be ready. The team anticipates that, unless there is another La Niña, which is extremely unlikely, there will be…a very large fire season across Australia next year.
The climate cause
The reason for the disturbing fire trend in forests is obvious: climate change.
The study evaluated eight major causes of fire, finding that there has been a sharp increase in the number of days in which conditions are favorable for dry lightning have soared, and the number of super-hot days has jumped up as well. Recently, there has also been less rainfall causing soils to dry out and stay dry. All of these factors collide setting up a forest to burn.
All of these elements can be linked to climate change, with Australia’s temperature rising by 1.4°C since 1910.
These factors are incorporated into the Forest Fire Danger Index (FFDI), a measure of the danger of a bushfire on a specific day and location.
Several previous studies have revealed that Australia is now experiencing more and more extremely high fire danger days, as measured by the FFDI.
But according to the research in this study, even a tiny variation in the number of these days can result in a large expansion in burned regions.
Researchers describe that there is a tight-knit, exponential relationship between the number of high fire danger days, and the resulting area burned. It is suggested that for each additional very high fire danger day over a baseline of 25 per year, there was a 21% increase in the area that was burnt.
The study shows that the relationship between FFDI and fire days is so tightly relational, that it could have “predicted” the unexpectedly large area burned in 2019.
Would prescribed burning reduce the size of fires?
Many experts have argued that, in the wake of the Black Summer, fire prevention efforts such as prescribed burning might help reduce fires. However, this study found no indication for this on a broad scale. Though there was some variation, there was no clear relationship was established between total area burned and management efforts.
Prescribed burns reduce approximately 1% of the available fuel. Whatever impact reducing fuel load had on the total burned area was completely offset by the influence of climate change.
While data on fuel loads does go back very far. Canadell relates that it’s hard to believe that fuel loads would have played a substantial role in what has been seen – the driving force is weather and climate.
The lack of influence prescribed burning seems to have is concerning because it is one of the few factors we can control. But, it would be difficult to increase the amount of prescribed burning, especially owing to a shortage of emergency-service personnel.
The CSIRO’s Mick Meyer, co-author of the study relates that when efforts of prescribed burning are primarily aimed at protecting assets like homes and property it does an excellent job at preventing flames from spreading.
What does this signify for people, animals, and the environment?
The blazes are a serious risk to infrastructure, including entire towns and homes being destroyed. Additionally, the smoke from the fires is a health hazard, causing asthma attacks and substantially raising asthma and heart-related hospitalizations.
Not only do frequent fires endanger entire ecosystems, but they also pose a direct hazard to native creatures. Frequent fires will destroy the rainforest regions because of their extremely low fire tolerance.
As the fire season increases in length, there eventually will not be an offseason. The personnel managing firefighting efforts will not get a break.
The autumn and winter seasons will become increasingly important as a fire season in the southeast corner of Australia. There will be increasing difficulty in managing it, and it will become even more difficult to live and work around these forests – including those capital cities adjacent to forests.
Where did the data originate?
This research is the result of a significant effort to accumulate fire data from all across the country. A national database does not exist, but state and territorial data are collected.
The researchers combined data from a variety of different sources – both ground and aerial – from across the country, stretching back 90 years. To ensure that their results were solid, they also utilized 32 years of data from two more US sources: NOAA’s and NASA’s satellites.
In-depth studies such as this had not been conducted on any of these three data sources in the past. One researcher suggested that this will likely change in the future, and added that there needs to be a national-level data repository for all things relating to fire.
