Climate Change: Wildfire Fuel And Future Risks

Climate change is causing an increase in the frequency and severity of wildfires across the globe. The warming climate, dry forests, and changing weather patterns are fuelling these fires, which have unprecedented impacts. The evidence connecting the climate crisis and wildfires is clear: rising temperatures and reduced moisture are leading to drier conditions and extended fire seasons. This is causing larger amounts of stored carbon to be released into the atmosphere, further exacerbating climate change.

Warmer, drier conditions increase the frequency, size and severity of wildfires

Research shows that climate change has led to warmer, drier conditions, which in turn has increased the length and activity of fire seasons. A 2016 study found that climate change doubled the number of large fires in the Western United States between 1984 and 2015. A 2021 study supported by the National Oceanic and Atmospheric Administration (NOAA) concluded that climate change has been the main driver of the increase in fire weather in this region.

The drying of organic matter and vegetation is a key factor in the spread of wildfires. Warmer temperatures evaporate moisture from the soil, shrubs, grass, trees, and other vegetation. This drying effect turns organic matter into kindling, which helps fires catch and spread. Once a fire starts, warmer temperatures and drier conditions can make it spread faster and burn hotter, making it harder to extinguish.

The impact of climate change on fire seasons is significant. Higher average temperatures and earlier snowmelt prolong the fire season, giving wildfires more time to ignite and spread. Severe drought and low humidity have extended the length of fire seasons faster than initially predicted by climate models. On average, the fire season has lengthened by 27% globally, with notable increases in the Amazon, the Mediterranean, and western North America.

The combination of rising temperatures and changing precipitation patterns contributes to the creation of warmer, drier conditions. Heavier-than-usual rainfall can lead to increased vegetation growth, providing more fuel for fires. This, coupled with longer, hotter summers, creates the ideal environment for wildfires to start and spread.

The impact of warmer, drier conditions on wildfires is evident in the increasing frequency, size, and severity of these fires. The evidence connecting the climate crisis to extreme wildfires is clear, and urgent action is needed to address this growing threat.

Climate change lengthens fire seasons

Research has shown that changes in climate create warmer and drier conditions, leading to longer and more active fire seasons. Warmer temperatures and a thirstier atmosphere due to human-caused climate change have increased the aridity of forest fuels during the fire season. These factors were responsible for over half the observed decrease in the moisture content of fuels in western US forests from 1979 to 2015, and the doubling of forest fire burned areas over the period 1984-2015.

In the US, climate change has extended the fire season by 27% on average, with more pronounced lengthening in the Amazon, the Mediterranean, and western North America. These are all places that have been devastated by wildfires in the last five years.

Projections show that in some forest types in the western US, an average annual temperature increase of just 1°C would increase the median burned area per year by as much as 600%. In the southeastern US, models predict an increase in areas burned by lightning-ignited wildfires.

The lengthening of fire seasons is driven by a combination of factors, including severe drought and low humidity, which have accelerated the rate of fire season extension beyond what was initially predicted by climate models.

Climate change increases lightning strikes, which spark wildfires

Lightning is the most common natural cause of wildfires. The heat of a single lightning strike can cause a tree's moisture to evaporate and spark a flame. As global temperatures rise due to climate change, the air contains more evaporated water, increasing the chance of thunderstorms and lightning strikes.

Research has shown that lightning strikes are expected to increase by about 12% for every degree Celsius the global average temperature increases. This means that if the current rate of climate change continues, the planet will experience around 50% more lightning strikes by 2100.

In addition to increasing the frequency of lightning strikes, climate change also contributes to drier conditions that provide fuel for wildfires. Higher temperatures cause moisture to evaporate from soil and vegetation, drying out trees, shrubs, and grass, and turning leaf litter and fallen branches into kindling.

The combination of increased lightning strikes and drier conditions creates a dangerous situation that increases the risk of wildfires. This was evident in California in 2020, when dry lightning sparked thousands of lightning strikes over a couple of days, setting off several wildfires that burned nearly a million hectares of land.

To reduce the risk of lightning-induced wildfires, it is essential to address the root cause of climate change by reducing greenhouse gas emissions and taking steps to mitigate global warming.

Poor forest management makes environments more susceptible to wildfires

However, despite this long history of forest management, experts say that decades of mismanagement have led to choked forests. Federal, state, and local agencies have prioritized fire suppression over prevention, focusing on hiring and training firefighters, buying and maintaining equipment, and educating the public on fire safety. This has resulted in a backlog of trees in forests now choked with brush and other dry fuels. As a result, the Western US is enduring devastating fire seasons, with bigger, hotter, and more destructive wildfires.

One of the main issues is that fire-suppression efforts have effectively removed fire as a thinning agent from most forests. In the past, relatively frequent, low-intensity surface fires burned in many forests, primarily carried by ground vegetation such as grasses. However, livestock grazing on public lands has reduced the amount of grasses, and fires now burn only when there is a significant buildup of woody debris, often leading to severe fires.

Another factor is logging operations, which have historically removed the largest and most fire-resistant trees. The young trees that replace them are highly susceptible to fire and serve as "fire ladders," allowing the fire to reach the canopy. Additionally, with denser tree cover, there is an increased danger of bigger fires.

To address these issues, experts are calling for a shift in focus towards managing healthy forests that can better withstand fires. This includes thinning and prescribed burns to reduce the fuel load and prevent uncontrolled, catastrophic fires.

Wildfires release carbon dioxide, contributing to climate change

Wildfires are unplanned fires that burn in forests, grasslands, and other ecosystems. They emit large amounts of carbon dioxide, contributing to climate change. In 2021, wildfires emitted 1.76 billion tonnes of carbon into the atmosphere globally, according to the European Union's Copernicus Atmosphere Monitoring Service. This amount is more than double Germany's annual CO2 emissions.

Wildfires release stored carbon from trees and other vegetation in the form of carbon dioxide and other greenhouse gases such as methane and nitrous oxide. The impact of wildfires on the atmosphere is significant due to the large amounts of carbon emitted and the subsequent decomposition of trees killed by the fires, which releases additional carbon dioxide over time. The combined effect of direct emissions and indirect emissions from tree decomposition contributes to a substantial increase in greenhouse gas concentrations.

The relationship between wildfires and carbon emissions is a vicious cycle. Increased global emissions lead to higher temperatures, creating drier conditions that are more prone to wildfires. As the frequency and severity of wildfires increase, more emissions are released into the atmosphere, further exacerbating climate change. This positive feedback loop intensifies the impacts of wildfires on the environment.

Additionally, the decomposition of trees killed by fires contributes to a net increase in carbon dioxide levels. While regrowth of forests can help remove carbon from the atmosphere, the immediate impact of wildfires is a significant release of greenhouse gases. This release disrupts the natural balance of carbon dioxide levels and contributes to the overall warming of the planet.

To break this cycle, it is crucial to address the underlying causes of climate change. Reducing greenhouse gas emissions and improving forest management practices can help mitigate the impacts of wildfires on the environment and slow down the rate of climate change. By taking proactive measures, we can work towards minimizing the frequency and severity of wildfires and their contribution to global carbon dioxide emissions.

Frequently asked questions