Global Expansion of Wildland-Urban Interface (WUI) and WUI fires and the impact of WUI fires on global air quality

Fires in the wildland-urban interface (WUI) are an important issue globally. To understand the change of WUI, we develop a 9-km Worldwide Unified Wildland-Urban Interface (WUWUI) database for 2001-2020 with Random Forest models and satellite data. We find that WUI has been increasing in all populated continents from 2001 to 2020 and the global relative increase is 24%, with the largest relative increase (~59%) over Africa. Global total fire counts decrease by 10% from 2005 to 2020, whereas the WUI fraction of fire counts increases by 23%. The global total burned area decreases by 22% from 2005 to 2020, whereas the WUI fraction of burned area increases by 35%. These are mainly due to the expansion of the WUI area. On all the populated continents, the WUI fractions of fire counts are higher than the WUI fractions of burned area, implying that WUI fires tend to have smaller sizes than wildland fires. Despite the growing importance of WUI fire, the impact of WUI fires on air quality and health is largely understudied and less understood at the global scale compared to that of wildland fires. Building on the recent progress, here we present the first global analysis of the effects of WUI fires on air quality impacts and health using an state-of-the-art atmospheric chemistry model – the Multi-Scale Infrastructure for Chemistry and Aerosols model (MUSICAv0).