Irvine, Calif. — Researchers at the University of California, Irvine and other institutions have spotted a contradiction in worldwide wildfire trends: Despite a 26 percent decline in total burned area from 2002 to 2021, the number of people exposed to wildfires has surged by nearly 40 percent.
The study, published today in Science, revealed another statistic that may come as a surprise to people who rely primarily on Western news sources: While high-profile wildfire disasters in the United States, Canada and Australia often dominate headlines, the researchers found that 85 percent of all human exposures to wildfires during that period occurred in Africa.
Just five central African countries – Congo, South Sudan, Mozambique, Zambia and Angola – accounted for half of all global human exposure. In contrast, the United States, Europe and Australia collectively constituted less than 2.5 percent of the total.
"Nevertheless, the western U.S. and particularly California are hot spots of intense fires globally," said senior author Mojtaba Sadegh, an associate professor of civil engineering at Idaho's Boise State University who earned a Ph.D. in civil and environmental engineering at UC Irvine in 2015. "Our previously published study shows that California experiences a disproportionately large share of U.S. fire impacts, accounting for 72 percent of human exposures despite comprising 15 percent of the nation's burned area."
The researchers analyzed population data and more than 18.6 million fire records from 2002 to 2021 to find that an estimated 440 million people worldwide were exposed to a wildfire encroaching on their home during this period – a number roughly equivalent to the entire population of the European Union. They discovered that human exposure to wildland fire increased by 7.7 million people, an average of 382,700 persons per year during the study period. This surge in human exposure was prompted not by a global jump in fire activity but primarily by population growth and migration into fire-prone landscapes.
Another factor illuminated by the research is a significant rise in the intensity of wildfires in North and South America. This is linked to the climate change-driven amplification of "fire weather," which includes conditions like increased heat, lower humidity and strong winds.
Extreme fire weather has grown by more than 50 percent over the past four decades globally.
When combined with such human activities as land development and historical fire suppression practices, this trend has led to an escalating risk of destructive fires in regions like California. The frequency of conditions conducive to extreme-impact wildfires (like the 2025 Los Angeles fires) quadrupled from 1990 to 2022 across the state.
In Europe and Oceania, the study noted a decline in wildfire exposures, mainly because of population shifts from rural to urban areas. This highlights how both social and environmental factors play critical roles in shaping wildfire risk.
"The global paradox of decreased burn area and increased human impacts we uncovered … is due largely to an increasing overlap between human settlements and fire-prone landscapes," said co-author Amir AghaKouchak, UC Irvine Chancellor's Professor of civil and environmental engineering.
Underscoring a growing human vulnerability to wildfires – particularly in regions that receive little international attention – the research emphasizes the urgent need for proactive mitigation strategies to protect communities from the burgeoning threat of wildfires. These include vegetation management techniques like prescribed fires, public education and engineering solutions to reduce human-caused ignitions.
"As climate change intensifies fire weather and global populations continue to expand into fire-prone zones, proactive mitigation will be increasingly critical to reduce the risk of future wildfire disasters," AghaKouchak said.
Study collaborators included Matthew Jones of England's University of East Anglia; Seyd Teymoor Seydi of Boise State University; John Abatzoglou and Crystal Kolden of UC Merced; Gabriel Filippelli of Indiana University Indianapolis; Matthew Hurteau of the University of New Mexico; Charles Luce of the U.S. Department of Agriculture Forest Service's Rocky Mountain Research Station in Boise; and Chiyuan Miao of Beijing Normal University. Funding was provided by the U.S. National Science Foundation.
About the University of California, Irvine: Founded in 1965, UC Irvine is a member of the prestigious Association of American Universities and is ranked among the nation's top 10 public universities by U.S. News & World Report. The campus has produced five Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UC Irvine has more than 36,000 students and offers 224 degree programs. It's located in one of the world's safest and most economically vibrant communities and is Orange County's second-largest employer, contributing $7 billion annually to the local economy and $8 billion statewide. For more on UC Irvine, visit www.uci.edu .
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