Hero image provided courtesy of USGCRP, NCA4, Vol. 2.

TL;DR — In the midst of this year’s wildfire season, it’s clear to see the short-term effects of wildfires: declines in environmental health and ecosystem balance, significant damage to air quality, and subsequent negative health impacts on the respiratory symptom that can cause asthma attacks and other severe symptoms. As climate change accelerates and increasingly impacts our world today, it is also crucial that we consider the long-term impacts that these devastating wildfires may have, from causing severe illness to changing entire ecosystems. 

Wildfires in our world today

In the midst of this year’s wildfire season, our focus again turns to the immensely damaging ways in which wildfires affect air quality as well as human and environmental health.

Recent years have seen increasingly devastating wildfires hit the United States — particularly in the western portion of the country — and various other regions across the globe, where wildfires destroy habitats, livelihoods, and can even threaten the loss of life. California’s situation illustrates the rapid acceleration of the impact and intensity of wildfires: 

Since the 1980s, the size and intensity of wildfires in California have notably increased. Fifteen of the 20 largest wildfires in California history have occurred since 2000, and ten of the most costly and destructive fires to life and property in the state have occurred since 2015”

— California Department of Fish and Wildlife

In our world today, increasingly intense and frequent wildfires are brought on by climate change, which compounds historically dry conditions due to droughts with record-breaking heatwave events, causing fires to both spread more quickly and burn more area. 

According to a recent World Wildlife Fund (WWF) assessment, human activity is thought to be responsible for 75% all wildfires and the global fire season's length grew by an average of 19% from 1979 to 2013. Image courtesy of Martin Armstrong, Data Journalist at Statista.

While wildfires are known to have drastic short-term effects on air quality, human and environmental health, their consequences extend far beyond the period while the wildfire is actively burning. In fact, wildfires have many long-term effects on human health and the environment — and we still have a lot to learn about the impacts of large and megafires. 

The short- and long-term health impacts of wildfire smoke

While we do understand that wildfires and their smoke have severe negative impacts on human health, there is a lack of long-term studies looking at their health impacts over time. Researchers are still working to fully elucidate all the ways that wildfires affect health outcomes in the long term.

Research has found that not only does wildfire smoke contain the harmful pollutant of fine particulate matter (PM2.5) — whose particles’ small size allows the pollutant to be inhaled deep into the lungs and respiratory tract and cause extensive damage — but the PM2.5 found in wildfire smoke is also more harmful than the same pollutant from other sources. 

Research from the Scripps Institution of Oceanography at the University of California, San Diego finds PM2.5 pollution from wildfire smoke to be up to ten times more harmful than that coming from other sources like car exhaust, tailpipes, or factories. Toxicological studies looking at how wildfire smoke affects health saw an increase in respiratory hospitalizations from 1.3% to 10% from exposure to wildfire-specific PM2.5, compared to 0.67% to 1.3% for non-wildfire PM2.5.

Because wildfire smoke comes from environmental disasters rather than machinery or production, we also do not have the same policy lever on wildfire smoke pollution as we do for vehicle and smokestack emissions. This means that there is relatively little regulators can do to limit smoke events compared to industrial emission limits — although investing in better forest management through organizations like Blue Forest Conservation provides one viable route to battling wildfire smoke

Short-term impacts of wildfire smoke, particularly those affecting the respiratory system, are the more well-known health outcomes, including:

  • Immediate asthma attacks, coughing, and other respiratory symptoms
  • Increased hospital visits for lung and heart conditions
  • Irritation of the eyes
  • Stroke
  • Increased risk of premature death

While these short-term impacts are well-known, with the worsening wildfire seasons we see each year, it’s important to develop a better understanding of the long-term impacts that wildfires have on health.

Though not fully understood, research has been investigating the mechanism behind which wildfire smoke can have long-term impacts. Research from the Harvard John A. Paulson School of Engineering has found that when there is peat in the soil where a wildfire has burned — which is often seen in tropical forests — the peat can smolder for weeks, explaining one way that the impacts of the wildfire can continue even after the flames are extinguished.

What people don’t always realize is that the particles in the smoke can affect chronic conditions like heart or pulmonary diseases, and the current thinking is that the long-term health effects can be quite severe over a period of a year or even more. So someone may get a stroke next June in that region and not realize that it can be traced back to smoke exposure.”

— Loretta Mickley, senior research fellow in atmospheric chemistry at the Harvard John A. Paulson School of Engineering

Wildfire smoke exposure over a longer time period means systemic inflammation, and can therefore contribute to serious illnesses and chronic diseases like heart disease that can eventually lead to death.

In a 2012 study published in the journal Environmental Health Perspectives, [Sarah B. Henderson] and her colleagues estimated that short-term and long-term exposures to landscape fires cause about 339,000 deaths per year worldwide. ‘Fire emissions are an important contributor to global mortality,’ the researchers wrote."

— Johnston et al., 2012

Though wildfire smoke’s most obvious impacts are on the respiratory system, its emissions affect the entire body. Research suggests that air pollution might contribute to the development of diabetes, dementia, and other illnesses.

To learn more about the vast impacts that air pollution, like that coming from wildfire smoke, has on human health, read our blog taking a deep dive on the health impacts of air pollution here.

Research has found that the harmful particles of PM2.5 pollution have different impacts depending on their source. For example, the pollution from wildfire smoke, which includes PM2.5 in addition to sulfur dioxide, carbon monoxide, and other small particles that can easily enter the body, has different impacts than diesel smoke. 

In the same vein, air pollution resulting from wildfires depends on what was burned during the fire, as some types of biomass smoke are more toxic than others. One animal study found that eucalyptus and pine tree smoke was significantly more toxic than that from red oak trees, as was wildfire smoke from burning furniture, houses, cars, and other man-made materials.

Air quality can change very rapidly during wildfires as illustrated by the video below, especially when factors like wind are at play which can shift the trail of smoke. Air quality can change depending on the intensity of the flames, the materials being burned, and the path that the fire is moving in, among other factors. Given the rapid and dynamic nature of wildfires, low-cost air quality sensors that measure air quality in real-time can be valuable tools for understanding air quality and air pollution exposure during wildfire events.

Earlier this month in Weed, California, a wildfire forced mandatory evacuations for the town’s residents. The video above shows the wildfire smoke’s movement as the fire continued to burn.

Wildfires not only have impacts on human health while they are burning but also afterward during the wildfire cleanup process. After homes and buildings have burned during a wildfire, the debris left behind exposes hazardous materials — such as the harmful mineral asbestos that can be present in older homes.

Though we have a good understanding of the more immediate effects of wildfires, more time is needed to study their long-term effects further, especially on human health — such as whether those exposed to wildfire smoke over a longer time period develop related diseases, such as heart disease, diabetes, or cancer as a result. 

How wildfires affect the environment

In the short term, wildfires can cause significant habitat damage, particularly by burning vegetation. Fires often destroy plants along the forest floor and smaller trees, destroying the food source and homes of many animals. Those plants that are able to survive the fires — such as larger trees whose branches the flames cannot reach — can become more susceptible to disease, fungus, and insects after the fire damage.

With the loss of vegetation, ground soil can become hydrophobic and resist water absorption, meaning more debris and sentiment can runoff during storms into larger bodies of water, polluting these sources. Flash floods can also occur after fires, introducing heavy metals from ash and soil into waterways.

These short-term effects can accumulate to even more significant long-term damage. Wildfires can change the physical, chemical, and biological qualities of water sources like streams, rivers, and lakes which are noticeable for years and even decades following a wildfire. 

Permanent ecosystem damage can also occur as a result of fires, especially when the usual cycle of small, controlled burns turns to rampant frequent, intense wildfires with accelerating climate change. When controlled, fires can aid in environmental health by promoting biological diversity, reducing debris buildup, and releasing nutrients in the soil. However, when too intense, fires destroy environments rather than contribute to their health.

The removal of natural fire from an ecosystem can lead to excess fuel buildup and changes in vegetation composition, which can increase the risk of uncharacteristically large high-severity fires”

— California Department of Fish and Wildlife

Forest health is a clear area significantly impacted by wildfires. Tree regeneration rates have decreased significantly this century compared to last, and significant forest damage can even lead to ecosystem change with forests turning to grasslands or shrubs.

This process only compounds on itself — as fires burn and release more carbon dioxide into the atmosphere, which acts as a greenhouse gas and can exacerbate climate change, the fires also destroy the trees that help remove carbon dioxide from the atmosphere.

In the long-term, wildfires can damage a forest’s sink strength, or its capacity to remove carbon dioxide from the atmosphere, as well as inhibit regrowth and change species composition. This means that wildfires are both increasing the amount of carbon dioxide being released and decreasing the amount that can be reabsorbed in forests.

The immediate impacts of wildfire, such as changes in the vegetation structure of an environment, can affect larger ecosystem health management such as biodiversity, groundwater management, forestry, recreation, and overall human safety in these outdoor spaces.

Atypically large patches of high-severity fire can hinder the ability of an ecosystem to recover, potentially undermining conservation of native biodiversity by long-term or permanent loss of native vegetation, expansion of non-native, invasive species, and long-term or permanent loss of essential habitat for native fauna.”

— California Department of Fish and Wildlife

The connection between wildfires and climate change

Just as wildfires are becoming increasingly severe and frequent as climate change accelerates, so too do they worsen certain aspects of climate change — primarily due to the significant amounts of greenhouse gases they emit.

Although the exact quantities are difficult to calculate, scientists estimate that wildfires emitted about 8 billion tons of CO2 per year for the past 20 years. In 2017, total global CO2 emissions reached 32.5 billion tons, according to the International Energy Agency” 

— Inside Climate News

However, because some of the carbon dioxide emissions from wildfires are offset by the renewed forest growth in burnt areas, it is estimated that wildfires make up five to ten percent of annual global CO2 emissions each year.

Wildfires have also been linked to a climate feedback loop, where wildfires and climate change can worsen the other in a constant cycle. 

Fires and the Climate Feedback Loop

Wildfires release pollutants such as CO2, causing there to be more carbon dioxide in the atmosphere, causing temperatures to increase, creating the perfect conditions for even more wildfires to ignite, creating this feedback loop. (Image source: World Resources Institute)

This means that climate change increasingly affecting our globe drives even more frequent and severe environmental disasters such as wildfires to occur. 

Protecting our world from wildfires

As environmental disasters such as wildfires continue to burn, leading to severe short- and long-term impacts on human and environmental health, we need more localized air quality in order to look more closely at how these wildfires are impacting individuals and communities.

We know that wildfire smoke is harmful to human health, environmental health, and climatic health — but we still do not fully understand all the ways that these devastating wildfires will affect us in the long term.

There is sometimes a gap in air quality data around wildfire events due to monitors going offline, making it difficult for officials and residents alike to make informed decisions to protect their health during wildfires. This means it is more important than ever to establish resilient air quality monitoring infrastructure — read our blog here to learn more.

Interested in measuring air quality as we take the step towards cleaner air and a healthier climate? Get in touch with our team to learn more about our Sensing-as-a-Service solution for governments, businesses, and community organizations, using our Clarity Node-S monitors and modules that do not depend on infrastructure like WiFi or power that can easily go down during environmental disasters.