Climate Change and Wildfires: How are they connected?

Hello! Given that wildfires have been all over the news lately, I thought they would make a good topic for a blog post. Specifically, we are going to discuss what ingredients are necessary for wildfires to start, and how climate change and wildfires are connected.

Wildfires have been increasing in the Western US since the 1980s. While there are normal fluctuations in wildfires cycles and climate patterns like El Nino which may impact wildfire frequency and intensity, it is clear that they are increasing.

Projections suggest that climate change will increase wildfire frequency and areas burned moving forward. 

Ingredients for a Wildfire:

Before we dive more into wildfires and how climate change exacerbates conditions for wildfires to ignite or spread, it’s first important to understand the ingredients for wildfires. 

The main ingredients needed for a wildfires include:

• Availability of dry vegetation (“dry fuel”)
• Hot and dry wind
• And human or natural fire ignition

The Two Kinds of Wildfires:

There are two main wildfire “regimes.” Understanding each and their limiting factors is also helpful in understanding how climate conditions impact wildfires.

1. Energy Limited Regime
   1. Some fires are limited by fuel flammability. These fires take place in relatively wet, densely forested ecosystems where plants and trees are plentiful. They are present year round. These are the types of fires typically seen in Northern California.
2. Moisture Limited Regime
   1. Some fires are limited by moisture. These fires thrive in relatively dry climates and use grass and low-density shrub vegetation as fuels. They are limited by fuel availability, meaning that if low amounts of grass or low-density shrub vegetation are available, there are fewer fires. These are the types of fires typically seen in southern California. 

How Climate Change Increases Conditions for Wildfires:

There are several ways climate change can increase the conditions needed for wildfires. Below several examples are listed, along with brief explanations.

1. Increasing temperature

First, climate change is increasing temperatures. Greenhouse gas emissions from human activity are increasing global temperatures, which make for more frequent and prolonged periods of optimal dry vegetation. This can help provide more fuel over longer periods of time for energy-limited fire regimes.

2. Earlier snow melts and earlier spring

Climate change is shifting the seasons. With shifts in seasons, snow is melting earlier, ushering in an earlier spring.  This seasonal shift extends the length of the wildfire season, meaning a longer stretch of time is available for fires to ignite and spread.

Earlier snow melts also mean drier summers. Drier summers mean more dry vegetation (“dry fuel”) available for wildfires to take hold of as fuel. 

3. Increased rainfall

Climate change is changing rainfall patterns and intensity. Increased rainfall one year leads to greater amounts of shrubs and grasses. A greater availability of grass and shrubs increases risks of wildfires in moisture-limited fire regime areas. 

What are the health effects of wildfires?

Wildfires present threats of immediate injury and death. 

Additionally, wildfires impact the air quality and can drastically change the AQI. Wildfire emissions contain Co, NO2, O3 (ozone), hydrocarbons like PAH, and PM (read more about that here), which can lead to respiratory illness.

The link between wildfires and cardiovascular disease is currently less clear; however, breathing in wildfire smoke is certainly known to be detrimental to human health in other ways.

*Read about what it means when your phone says poor air quality for sensitive groups here.

A Dangerous Feedback Loop?

As mentioned, wildfires emit carbon and other greenhouse gas emissions, thus contributing to the human-created greenhouse gas emissions fueling global warming.

Additionally, some forests, such as the Amazon forest, serve as major carbon sinks for carbon dioxide. If these forests disappear due to atmospheric climate change, there will be more carbon dioxide in the atmosphere, further exacerbating climate change.

So, some have suggested that wildfires and climate change together may act as a dangerous feedback loop, wherein climate change increases the likelihood of wildfires, and wildfires contribute to exacerbating climate change.

Take Home:

There are still many uncertainties when it comes to linking climate change to wildfires. However, increasing global temperatures and shifts in global precipitation and climate patterns are increasing conditions that allow wildfires to ignite and spread.