Irvine, California — Recent collaborative research led by experts at the University of California, Irvine, alongside colleagues from numerous global institutions, has uncovered a striking paradox in the recent dynamics of wildfires worldwide. While the total area burned by wildfires has declined by approximately 26 percent between 2002 and 2021, the number of people exposed to these fires has paradoxically surged by nearly 40 percent. This counterintuitive finding challenges prevailing assumptions about wildfire risk and highlights intricate interactions between human populations, land use, and climate-driven fire regimes.
Published today in the esteemed journal Science, the study rigorously analyzed over 18.6 million fire observations alongside detailed global population data spanning two decades. The researchers estimate that roughly 440 million individuals—equivalent to the population of the European Union—experienced wildfire exposure during this interval. Notably, the investigation reveals that this uptick in human exposure is not attributable to a global increase in wildfire activity. Instead, a demographic trend of expanding populations and migration into fire-prone landscapes significantly amplifies human vulnerability. This spatial convergence between human settlements and flammable ecosystems emerges as a critical driver behind rising wildfire exposure.
Strikingly, the study overturns widespread perceptions shaped by Western media coverage, which often casts North America and Australia as the epicenters of wildfire crises. The data show that a staggering 85 percent of all human wildfire exposures occurred across Africa. This continent, home to some of the world’s most extensive savanna and forest fire activity, sees widespread fire interactions with dense and growing populations. Five central African nations—namely Congo, South Sudan, Mozambique, Zambia, and Angola—alone account for half of the global total of wildfire exposures. In stark contrast, the United States, Europe, and Australia combined contribute less than 2.5 percent, underscoring the geographical skew in global fire-human interactions.
Despite Africa’s dominant share of wildfire exposure, certain regions in the western United States, particularly California, remain hotspots of intense and destructive fire activity. Mojtaba Sadegh, senior author and associate professor of civil engineering at Boise State University with academic ties to UC Irvine, remarks on the outsized impact California experiences. Their prior research highlights that although California accounts for only 15 percent of the burned land in the U.S., it suffers 72 percent of the nation’s human wildfire exposures. This disproportion underscores the serious challenges posed by population distribution, land management, and climatic conditions within this region.
The intensification of wildfire risk is intimately linked to climate change, which has exacerbated conditions favorable to large-scale fires. “Fire weather,” a meteorological concept encompassing elevated temperatures, decreased humidity, and stronger winds, has intensified globally by more than 50 percent over the last 40 years. These shifts create an environment that promotes more frequent, larger, and more severe wildfires. The American continents, in particular, have witnessed a notable rise in fire intensity, with consequences for ecosystems and communities alike.
California, long recognized for its vulnerability to wildfire disasters, has seen conditions conducive to extreme-impact fire events multiply substantially. Research cited by the study finds that between 1990 and 2022, the frequency of such conditions quadrupled in the state. These extreme events resemble recent catastrophic fire seasons, such as the devastating 2025 Los Angeles fires. Climate-driven exacerbations of fire weather couple synergistically with long-standing human land use patterns, including urban expansion into wildlands and historic suppression of natural fires, creating a complex and escalating hazard landscape.
Contrasting these trends in the Americas, Europe and Oceania have observed a decline in wildfire exposures. This reduction is largely attributed to demographic changes, especially population movements from rural, fire-prone areas into densely populated urban centers. This sociological transition helps explain diverging wildfire risks and demonstrates the importance of human settlement patterns in modulating fire exposure outcomes. The study illuminates how social behaviors and environmental changes together dictate evolving regional fire risk profiles.
Dr. Amir AghaKouchak, UC Irvine Chancellor’s Professor and co-author, frames the core paradox: the amount of land burned globally has declined, yet human exposure to wildfires has increased. This phenomenon is chiefly the result of the growing interface between human communities and fire-adapted ecosystems. As more people inhabit or move toward fire-prone regions, the potential for harm grows, even in the context of contracting burned acreage. This nuanced understanding challenges simplistic narratives equating burned area with human wildfire risk.
These findings point to an urgent need for proactive wildfire mitigation strategies that transcend traditional firefighting approaches. Given the heightened human vulnerability, especially in underappreciated regions such as Africa, comprehensive adaptation frameworks become imperative. Possible measures include employing sophisticated vegetation management techniques like prescribed burns to reduce fuel loads predictably, advancing public education programs to raise awareness about wildfire risks, and innovating engineering solutions that mitigate human-induced ignitions and enhance community resilience.
The escalation of wildfire threats in a warming world necessitates coordinated responses that integrate climate science, urban planning, and ecological management. With global populations continuing to expand into vulnerable landscapes, the window for effective mitigation narrows. The research team underscores that without such concerted efforts, future wildfire disasters will likely increase in frequency, scale, and societal impact. Their multi-disciplinary approach offers critical insights that can inform policymakers and stakeholders aiming to protect lives and infrastructure in the fire-prone twenty-first century.
The international research collaboration included specialists from several renowned institutions: Matthew Jones of the University of East Anglia, Seyd Teymoor Seydi of Boise State University, John Abatzoglou and Crystal Kolden from UC Merced, Gabriel Filippelli of Indiana University Indianapolis, Matthew Hurteau at the University of New Mexico, Charles Luce from the U.S. Department of Agriculture Forest Service’s Rocky Mountain Research Station, and Chiyuan Miao at Beijing Normal University. Financial support was provided by the U.S. National Science Foundation, enabling this comprehensive evaluation of global wildfire-human exposure patterns.
UC Irvine, established in 1965, stands as a premier research university in the United States, and its contributions to environmental engineering and earth sciences continue to be internationally influential. The findings articulated in this paper represent a pivotal advancement in the wildfire science domain, revealing previously underappreciated complexities in human-fire interactions. As the global climate continues to evolve, such research is indispensable for guiding adaptive strategies and safeguarding communities worldwide.
Subject of Research: Global wildfire trends, human wildfire exposure, climate change impacts on fire activity, demographic shifts and fire risk.
Article Title: Increasing global human exposure to wildland fires despite declining burned area
News Publication Date: 21-Aug-2025
Web References: http://dx.doi.org/10.1126/science.adu6408
References: Study published in Science, DOI: 10.1126/science.adu6408
Keywords: Wildfires, Climatology, Natural disasters, Fire weather, Human exposure, Population migration, Climate change, Vegetation management, Fire risk, Environmental engineering
