How Wildfires Threaten Human Health, Ecosystems, and Climate

The World Health Organization states that wildfires are increasing around the globe in frequency, severity and duration, heightening the need to understand the health effects of wildfire exposure. The risk of wildfires grows in extremely dry conditions, such as drought, heat waves and during high winds.

Impacts of wildfires on people’s health

First, wildfires create hazardous air. Wildfire smoke contains harmful pollutants like PM2.5, NO2, ozone, and aromatic hydrocarbons.

Wind-driven fires in Los Angeles have killed at least 25 people, destroyed around 12,000 homes, schools, and other buildings, and scorched over 40,000 acres since January 7.

Experts are focusing attention on health consequences that they say will reverberate for years after the danger has passed. Apart from the economic and property damages, the health impacts of wildfires should also be considered.

Smoke from burning cars, metal pipes, plastics, trees, and shrubs is toxic and emits very fine particulate matter known as PM 2.5. These can burrow deep into the lungs and can even infiltrate the bloodstream, causing cold- and flu-like symptoms in the short term and heart disease, lung cancer, and other chronic issues over time.

Additionally, the thick smoke that enveloped the city elevated its air quality index (AQI) to exceed 100, the limit typically seen during wildfires and at which the air becomes unhealthy to breathe for children, the elderly, and those with asthma. In some parts of the city, the AQI reached 500, a figure rarely seen and hazardous for everyone.

The WRI reports that the June 2023 wildfires in Quebec, Canada, caused more than 75 million people in the United States to experience unhealthy or hazardous air quality.

Research has shown a correlation between poor and hazardous air quality and the number of hospitalisations, particularly in the elderly, children, and those with chronic health conditions like asthma and heart disease.

Wildfires fuel climate change and vice versa

These fires emit greenhouse gases that fuel climate change, which increases heat and drought, intensifying wildfire risks and creating a dangerous cycle. As climate change causes hotter, drier conditions and urban sprawl increases, fire seasons start earlier and last longer. Wildfires are becoming more intense, burning more acres and disrupting transportation, communications, water, and utilities.

In 2021 alone, wildfires in boreal forests across North America, Europe, and Asia released 1.76 billion tons of carbon dioxide. If ranked as a country, wildfires would be among the world’s top ten emitters.

Wildfires threaten water security

Wildfires destroy forests, which are essential for maintaining water quality. Forested areas provide over two-thirds of the world’s drinking water and help prevent erosion and sedimentation.

After a wildfire, fewer trees and unstable soil lead to increased runoff, carrying sediment, ash, and pollutants into water sources. For example, the 2018 Camp Fire in California led to debris and toxins contaminating nearby water, forcing some utilities to stop using water from affected sources.

Wildfires damage the forest canopy and soil, disrupting these water-regulating functions and depleting freshwater supplies in affected areas.

Wildfires increase flooding risks

Healthy forests act as sponges as they absorb and store rainwater or runoff and can, hence, protect nearby communities from floods. But scorched and damaged forests lose their capacity to store runoff and instead increase the speed of water flow, bringing floodwater laced with ash and harmful sediments. This threat festered for years until vegetation grew back after the wildfires.

Wildfires create direct and indirect Economic Losses

In the US, the health impacts of wildfire smoke cost $16 billion annually. The cost of producing drinking water after wildfires increases between $10 million and $100 million, and lastly, flooding, a risk increased by wildfires, can cause costly infrastructure damage.

What can cities do to reduce wildfire risks?

WRI suggests that cities can do the following: They can play a key role in wildfire resilience and restoration efforts, acting as anchor investors in projects across state, federal, and private lands.

Cities’ agencies can also dedicate resources to support restoration but often face challenges with seasonal, underpaid work and limited resources. By investing in year-round staff, cities can bridge gaps in pre- and post-fire efforts.

Additionally, cities can help protect high-risk communities, especially those in wildland-urban interfaces, by reducing wildfire risks.

Lastly, cities contribute 70% of global carbon emissions and are responsible for reducing their GHG emissions, causing climate change. Reducing wildfire risks can yield significant economic benefits, potentially $24 trillion by 2050.