Rapid human expansion into natural landscapes, resulting in the growth of the wildland-urban interface (WUI), has heightened risks associated with wildfires.

Prof. WANG Jianghao’s team from the Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences has recently mapped global WUI changes in 2000, 2010, and 2020, revealing alarming upward trends in WUI areas.

This work, published in Science Advances, provides critical insights into how urbanization can intensify potential wildfire risks faced by people worldwide.

Against the backdrop of industrialization, the frequency and intensity of human activity have escalated, resulting in extensive natural land conversion into WUI areas. The most immediate conflict between human society and the Earth system is clustered in WUI, placing residents there at a higher risk of exposure to natural hazards, such as floods, landslides, and wildfires.

“The increased occurrence of extreme and large wildfires, exacerbated by climate change, necessitates urgent attention to these hazards in WUI areas,” said Prof. WANG.

Individuals living in or near WUI areas face elevated mortality risk due to exposure to flames and heat. Wildfire-related smoke can also increase the risk of illness and death even at a distance up to 1,000 km.

Therefore, understanding the dynamics of WUI growth and its underlying causes is critical for developing effective wildfire management strategies.

Conceptual diagram illustrating how human society and wildfire interact from distant wildlands to densely populated urban areas. (Image by GUO Yongxuan)

By 2020, global WUI areas covered 1.44% of the terrestrial surface, with approximately 1.2 billion people residing in these areas. Over the past two decades, WUI areas have expanded by more than a third, with 85% of new WUI areas identified between 2010 and 2020, the study showed.

The researchers noted that urbanization is the primary driver of WUI expansion, while changes in natural vegetation have a minimal impact. The acceleration of urban expansion also explains the uneven change in WUI areas.

The researchers’ further exploration of the spatial relationship between WUI zones and fire activity revealed that wildfires in and around WUI areas tend to be dense but low intensity, indicating that the WUI is a fire-prone area. From 2010 to 2020, small fires increased within a 1-km buffer of the WUI, while fire activities decreased at least 3 km away, which may be attributed to the increase in human activity.

In summary, the study shows that urbanization—as a key driver of WUI expansion—has contributed to increasing wildfire risks.