Are Wildfires Becoming More Frequent?

Check out this answer from Consensus:

The evidence is clear: wildfires are becoming more frequent and larger across various regions, driven by a combination of climate change and human activities. This trend has significant ecological and socio-economic implications, necessitating urgent attention from policymakers and land managers to mitigate the risks and adapt to the changing wildfire regimes.

Wildfires have long been a natural part of many ecosystems, but recent trends suggest that their frequency, size, and severity are changing. This article explores whether wildfires are becoming more frequent, drawing on recent research to understand the underlying factors and implications.

Increasing Frequency and Size of Wildfires

Several studies have documented a significant increase in the frequency and size of wildfires in various regions. For instance, an analysis of wildfires in the western United States from 1950 to 2019 revealed a near-exponential growth in fire frequency and size, with the mean size of fires more than doubling over the past few decades1. Similarly, research focusing on the 2000s found that average fire events in the U.S. have become up to four times larger and triple in frequency compared to the previous two decades2.

Regional Variations

The trend of increasing wildfire frequency is not confined to the United States. In temperate Australia, wildfires have also become more frequent and severe, particularly in eucalypt forests. Over 4.3 million hectares of eucalypt forest were burned by wildfire between 2003 and 2014, a figure roughly equivalent to the cumulative area burned in the previous 50 years3. This increased activity has significant implications for tree mortality and forest regeneration.

Climate Change and Wildfire Activity

Climate change is a major driver of the increasing frequency and size of wildfires. In the western United States, higher spring and summer temperatures and earlier snowmelt have been strongly associated with increased wildfire activity since the mid-1980s6. Similarly, rapid warming has been linked to more frequent wildfires in northeastern Australia, with the most frequent fires occurring during periods of rapid climate change8.

Human Influence

Human activities are also contributing to the changing wildfire regimes. Anthropogenic ignitions have increased, leading to larger and more frequent fires over longer fire seasons in the United States5. This trend is compounded by climate and land cover changes, creating a “new normal” of fire activity across continental scales.

Ecological Impacts

The increasing frequency of wildfires has profound ecological impacts. In temperate Australian forests, frequent severe wildfires have altered forest structure and composition, eroding the persistence of fire-tolerant tree species and shifting understorey dominance from shrubs to grasses9. High-severity wildfires have also become more common in southeastern Australia, with significant consequences for ecosystem dynamics4.

 

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Are wildfires becoming more frequent?

Lars Hein has answered Likely

An expert from Wageningen University and Research Centre in Environmental Science

At the global scale: yes. Dryland ecosystems are experiencing more frequent and severe periods of drought during which fire risks increase. Further research is needed to quantify the exact trends in fire occurrence.

 

Are wildfires becoming more frequent?

Bill Laurance has answered Likely

An expert from James Cook University in Conservation Science, Ecology

Yes, probably. It’s not happening everywhere, but in large parts of the Amazon, Siberia, Southeast Asia, Australia, and the Western U.S., wildfires are occurring with frightening frequency and intensity.

 

Are wildfires becoming more frequent?

David Lindenmayer has answered Near Certain

An expert from Australian National University in Conservation Science, Ecology

Yes – more frequent, widespread, severe – see review paper by Jones et al. 2020

 

Are wildfires becoming more frequent?

John D. Bailey has answered Near Certain

An expert from Oregon State University in Forestry Sciences

Yes. The data are very convincing and show an increase in wildfire activity in the US and globally beginning in the 1980s: area burned by wildfires, the average sizes of wildfires, the amount of effort and expense it takes to fight them, and the area that burn at high intensity. The 1980s marked the end of relative cool/moist/stable climatic period and decades of very active land management on private and public lands in the US – lots of grazing and harvesting (fuel/carbon removal), road construction, workers on the land to quickly extinguish fires while they were small, and an effective firefighting system. Since the 1980s, though, management and harvesting on public lands in western US has really slowed and, together with fire exclusion in these forests, we’ve had decades of steady fuel accumulation in overly-dense, carbon-rich, high-biomass forests – lots of acres with lots of fuel, and those acres are more connected to one another and to human values (homes, communities, recreation areas, watersheds, wildlife habitat) than ever before. In the state of Oregon, 60% of the forests are federally owned and 90% of each year’s tree growth on federal lands just accumulates in the forest, much of it as dead material.  Then, we have to add in climate change that has created longer fire seasons globally, higher temperatures, drier fuels and conditions that favor high-intensity wildfire, and (finally) more humans to start fires and to be impacted by fires. So there is no surprise that wildfires have become more frequent and larger, and that trend will likely continue until we change behaviors.

 

Are wildfires becoming more frequent?

Colin Beale has answered Uncertain

An expert from University of York in Ecology, Conservation Science

Whether or not wildfires are becoming more or less frequent depends entirely on where you look, and the timeframes over which the answer is considered. It also depends somewhat on your definition of wildfire: because people are part of nature and indigenous people and the landscapes they live in have often had an extremely long time to coevolve, I would consider indigenous land management practice an important part of wildfire. 

As a very broad overview, in places where fires were once a regular and frequent part of the landscape, fire frequency has declined. For example, across most of the African savannahs where our ancestors have been lighting fires for longer than our own species has existed, fire frequency today is lower, as a consequence of land conversion and high grazing pressure removing fuel to support fires. Many forests in Australia and North America also once experienced regular fire, with fire suppression a relatively recent goal. 

On the other hand, in many landscapes where fire has been frequent, there is a recent increase, largely as a consequence of hotter, dryer climates associated with climate change. These include the large fires in UK peatlands and many of the catastrophic fires we have seen in temperate landscapes in recent years.

 

Are wildfires becoming more frequent?

J. Rodrigo Garcia del Campo has answered Likely

An expert from Centro Nacional de Biotecnologia in Ecology

Yes, and unfortunately, they are becoming also more destructive. An increase in wildfires is considered an indicator of climate change: the consequences of the change that make the soil moisture evaporate and make climates drier and more arid make vegetation more flammable.

 

Are wildfires becoming more frequent?

Camille Stevens-Rumann has answered Near Certain

An expert from Colorado State University in Forestry Sciences

Wildfires are becoming larger, burning at higher severity and in some places burning at higher frequency.

 

Are wildfires becoming more frequent?

Alexander Lees has answered Near Certain

An expert from Manchester Metropolitan University in Conservation Science

Yes, climate strongly influences global wildfire activity, areas which have been historically unaffected by wildfires – e.g. undisturbed Amazonian forests are now suffering from them for the first time, however that generality hides a lot of regional variation over the centuries.

 

Are wildfires becoming more frequent?

Matthew Harris has answered Likely

An expert from Keele University in Climate science

In short, yes. The recent release of the IPCC’s 6th assessment report, Climate Change 2021: The Physical Science Basis, has made clear that the frequency and severity of wildfires, and fire weather as a whole, is set to increase as the planet warms to 1.5C above the pre-industrial average. More specifically, the report’s Summary for Policymakers (SPM) asserts with medium confidence that “some regions of all inhabited continents” will experience increased fire weather under the now all but certain 1.5C scenario (SPM A.3.5). If the planet warms to 2C above the pre-industrial average, the likelihood of increased wildfires becomes even greater (SPM C.2.4). Also concerning is the fact that wildfires are a positive feedback loop – fires emit carbon dioxide, thereby worsening global warming, and in turn increasing the frequency and severity of fire weather (SPM B.4.3).

 

Are wildfires becoming more frequent?

Paul Hessburg has answered Uncertain

An expert from United States Forest Service in Forestry Sciences

Not in many places. In geographic areas with a Mediterranean or continental climate, the converse is often true; most wildfires are extinguished using modern fire suppression techniques. However, in these same places, wildfires are becoming more severe. Fire suppression over the 20th and 21st centuries allowed forests to change in ways that I described above. Now suppression is failing to suppress all fires, especially those occurring during the worst fire weather days and during periods of persistent drought. These escapes occur because suppression resources may be limited or fire behavior overwhelms the available resources and direct attack methods become unsafe for people directly involved in the suppression action. In the US, we suppress 97-98% of all fire starts each year. It is the 2-3% of fire starts that burn on severe fire weather days that are burning the bulk of the western US landscape.

In some forests, this scenario is clearly not the case and fires are becoming more frequent. In these latter forests, climate change is occurring so rapidly that fires are a recent addition to the forest ecology and there is limited precedent for the changes. In these cases, many of the native tree species can be maladapted to an expanding fire ecology.

In still other cases, humans intentionally set fires for a variety of reasons, and fire frequency may or may not be increasing. What is clear is that these intentionally lit fires are not to improve the fire ecology or to reduce fuels. Instead they are lit to clear land for agriculture or other purposes, or to salvage the trees, or obtain employment suppressing the fire. There are other reasons as well.

 

Are wildfires becoming more frequent?

Joshua M. Johnston has answered Likely

An expert from Canadian Fire Service in Forestry Sciences

Certainly in some regions wildfires are becoming more frequent owing to an overall trend towards increasing fire danger under climate change combined with increased ignition events (lightning and/or human). However, there are also regions where the climate change trend is lowering the overall wildfire potential, but on the whole globally the planet in general is progressing towards increased fire danger. That said, there is a big difference between fire potential and fire occurrence, and the fact that our wildlands have the right weather conditions to burn does not mean that there will be a fire – that requires ignitions. 

Ignition is essential to increase the frequency of wildfires. Globally human activity is the dominant cause of fire, whether it is agricultural, land clearing, conflict driven, or just the by product of industry (e.g. railways, forestry, etc). However, lightning caused fires are a dominant source in certain more remote regions as well. In the case of Canada, there is a decreasing trend in the number of human caused ignitions, while the number of lightning fires is rising – leading an overall increase in fire frequency and a shift in the drivers of fire occurrence.

Finally, fire frequency is not necessarily as important as fire size. That is to say, large numbers of small fires near human infrastructure are often suppressed quickly, while remote fires are often able to grow to extremely large sizes. You can imagine that a having 10,000 small short lived fires would be very challenging to fire managers, but have 100 remote fires that are > 100,000 ha would have the ability to release vast amounts of carbon into the atmosphere and significantly impact public health and air quality as far away as another continent. There is a trend towards increasing fire size under climate change as well, and it is equally worrying. Notably, the increase in frequency is also linked to the increase in area burned. When surges in fire activity occur, often times fire managers are unable to keep up with the new fire arrivals and inevitably some escape containment and become the massive fires I just mentioned.

 

Are wildfires becoming more frequent?

Paul Hessburg has answered Uncertain

An expert from United States Forest Service in Forestry Sciences

Not in many places. In geographic areas with a Mediterranean or continental climate, the converse is often true; most wildfires are extinguished using modern fire suppression techniques. However, in these same places, wildfires are becoming more severe. Fire suppression over the 20th and 21st centuries allowed forests to change in ways that I described above. Now suppression is failing to suppress all fires, especially those occurring during the worst fire weather days and during periods of persistent drought. These escapes occur because suppression resources may be limited or fire behavior overwhelms the available resources and direct attack methods become unsafe for people directly involved in the suppression action. In the US, we suppress 97-98% of all fire starts each year. It is the 2-3% of fire starts that burn on severe fire weather days that are burning the bulk of the western US landscape.

In some forests, this scenario is clearly not the case and fires are becoming more frequent. In these latter forests, climate change is occurring so rapidly that fires are a recent addition to the forest ecology and there is limited precedent for the changes. In these cases, many of the native tree species can be maladapted to an expanding fire ecology.

In still other cases, humans intentionally set fires for a variety of reasons, and fire frequency may or may not be increasing. What is clear is that these intentionally lit fires are not to improve the fire ecology or to reduce fuels. Instead they are lit to clear land for agriculture or other purposes, or to salvage the trees, or obtain employment suppressing the fire. There are other reasons as well.

 

Are wildfires becoming more frequent?

Joshua M. Johnston has answered Likely

An expert from Canadian Fire Service in Forestry Sciences

Certainly in some regions wildfires are becoming more frequent owing to an overall trend towards increasing fire danger under climate change combined with increased ignition events (lightning and/or human). However, there are also regions where the climate change trend is lowering the overall wildfire potential, but on the whole globally the planet in general is progressing towards increased fire danger. That said, there is a big difference between fire potential and fire occurrence, and the fact that our wildlands have the right weather conditions to burn does not mean that there will be a fire – that requires ignitions. 

Ignition is essential to increase the frequency of wildfires. Globally human activity is the dominant cause of fire, whether it is agricultural, land clearing, conflict driven, or just the by product of industry (e.g. railways, forestry, etc). However, lightning caused fires are a dominant source in certain more remote regions as well. In the case of Canada, there is a decreasing trend in the number of human caused ignitions, while the number of lightning fires is rising – leading an overall increase in fire frequency and a shift in the drivers of fire occurrence.

Finally, fire frequency is not necessarily as important as fire size. That is to say, large numbers of small fires near human infrastructure are often suppressed quickly, while remote fires are often able to grow to extremely large sizes. You can imagine that a having 10,000 small short lived fires would be very challenging to fire managers, but have 100 remote fires that are > 100,000 ha would have the ability to release vast amounts of carbon into the atmosphere and significantly impact public health and air quality as far away as another continent. There is a trend towards increasing fire size under climate change as well, and it is equally worrying. Notably, the increase in frequency is also linked to the increase in area burned. When surges in fire activity occur, often times fire managers are unable to keep up with the new fire arrivals and inevitably some escape containment and become the massive fires I just mentioned.

 

Are wildfires becoming more frequent?

Chelene Hanes has answered Likely

An expert from Canadian Forest Service in Forestry Sciences

Yes, although fire frequency isn’t typically a metric we use. We more commonly look at number of fires and area burned. Across Canada these have increased, but there are some caveats as Josh mentioned.

1)     The increases are not consistent across the country. Fire activity in the West is showing more significant increases in both area burned and number of fires.

2)     Across the country lightning caused fires overall are on the rise and they typically result in larger area burned. Human caused fires are on the decline overall.

3)     The fire season is getting longer overall.

4)     The large fires are getting bigger.

So I think it is safe to say in the boreal of Canada fire activity is increasing. I haven’t looked at frequency directly and that might be a little different because although the number of fires is increasing, the fire season is getting longer so the frequency of occurrence may not be changing as much as we think. But by saying the fire frequency is decreasing we are also missing the point that overall fire activity is increasing significantly.