The recent increase in wildfires around the world is frequently linked to the hotter and drier weather conditions caused by climate change. However, a UC Riverside study discovered that the impact of rising carbon dioxide (CO2) levels on plant growth may actually be a more significant factor.
“The reason things are burning is not just because it’s hotter, but because there’s more fuel in the form of plants,” explained study author James Gomez, a doctoral student in Earth and planetary sciences at UCR.
This finding and a description of the eight model experiments that led to it have been detailed in Communications Earth & Environment.
In order to convert light into food through photosynthesis, plants need CO2. With the increasing levels of CO2 being added to the atmosphere from burning fossil fuels for heat, electricity, and transportation, plants are able to use the extra CO2 to produce carbohydrates.
Hydrates are important for the growth of plants, and when they are lacking, it leads to an increase in biomass that is more prone to burning. In today’s climate, heat waves and drought are more common than they were 50 years ago, causing plants to wither and die, making them more susceptible to burning. The models used in the study accounted for the effects of these conditions on plants, as well as the different types of plants and the increase in atmospheric CO2. According to UCR professor of Earth sciences Robert Allen, warming and drying are still significant factors in wildfires, as they create conditions that make the additional plant mass more flammable.
The research team examined models that all assumed a simplified 1% annual rise in atmospheric CO2 levels since 1850. This idealized increase was used to isolate the impact of the greenhouse gas on wildfires.
“These experiments primarily focus on the influence of CO2 on changes in wildfire activity,” Gomez explained. “That’s the only variable that changes in these models. Other factors affecting climate change and wildfire activity remain constant over time,” Gomez added. “This includes, for example, variations in other greenhouse gases such as methane, as well as changes in land use.”
Seasons are significant factors in the promotion of wildfires, and fires tend to occur more frequently during “fire seasons.” Dry, windy conditions contribute to the rapid spread of flames, leading to a larger burned area. However, according to Gomez, the increase in fires during hotter seasons is mainly due to fuel load rather than an increase in the number of what some consider ‘fire weather’ days.
As a result, megafires can occur outside of traditional fire seasons. For example, the largest wildfire on record in Texas, with over a million acres burned, occurred this past February.
The researchers are hopeful that their findings will help in the prevention and management of wildfires.
The findings of this study can serve as motivation for further research on the causes of the increase in wildfires. It is also hoped that policymakers will recognize the urgent need to reduce the amount of CO2 being released into the atmosphere. “Improving fire control and implementing more prescribed burns to reduce plant fuel are necessary. We also need to eliminate old vegetation,” stated Gomez. “However, the most effective way to decrease wildfires is to address our carbon dioxide emissions. We need better emission control immediately.” (Allen, R. J., Gomez, J., Larry, L.)W. Horowitz, Elena Shevliakova. Enhanced future vegetation growth with elevated carbon dioxide concentrations could lead to an increase in fire activity. Communications Earth & Environment, 2024; 5 (1) DOI: 10.1038/s43247-024-01228-7